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When our VAT40 died at the Ford/Jeep dealer, the shop foreman and service manager opted for what appeared to be a suitable succedaneum. The new ARBST came off the MAC tool truck for a cash exchange of about $1700. The VAT40’s impeccable ability to condemn an alternator stator had spoiled us dreadfully and I got burned a time or two with the new machine, which would tell us the stator was bad when it was actually good. I found myself doing an o-scope test on every alternator to back up the diagnosis when I got the red ‘stator’ light on the machine.
Another non-credible test was the injector flow meter procedure on the Rotunda injector cleaner/tester supplied to Ford dealers in the late 80s. This machine cost 2000 and was outfitted a pump, a regulator, and a small fuel tank with flow meters with color bands for the various injectors – it was designed to flow fuel through the injector at a fixed pulse width, and if the floating ball in the glass tube indicated fuel flow that was in the colored band matching the injector, that nozzle passed the test. In theory it was great, but in the shop it was a liar. I repeatedly saw injectors pass the flow test before and after cleaning, but the vehicle would run better anyway, so that flow test was a waste of my time and dumped it from my routine.
Then there are tried and true methods of troubleshooting that don’t cost much.
Remember my method of wiring a test light in series with a cooling fan motor and a battery and a quick turn through of the motor? You can immediately condemn a bad motor that way. If the light ever goes out during that test, the motor is junk. That test can easily be done at the fan relay socket without removing the fan if you’re a sharp cookie.
Using the in series amp measurement function of a cheap DVOM (set the meter up for 10 amps and use it like a jumper wire to bypass the fuel pump relay), a reading less than 2 amps with a humming fuel pump tells you the tank is empty. A normal pump that is actually moving fuel will show about 8 amps depending on the vehicle.
And low-cost tests like this aren’t limited to electrical stuff. Bump the A/C compressor clutch that fails to engage hot, and if it clicks in, the air gap needs to be set.
Fouled Up Five Hundred
At the risk of belaboring the unreliable test equipment point, let’s take a peek at a 2005 Ford with 68k on the odo, a vehicle that kept throwing the wrench light and “Fail Safe Engine” message and a nasty failure to accelerate. This unit has electronic throttle control with three potentiometers in the pedal, a motor and a sensor on the throttle body, and a PCM strategy to limit throttle response if the pedal pots don’t agree with each other. About once a day this Five Hundred would drop into Fail Safe Engine mode without warning but a key cycle would temporarily return things to normal.
With the Genisys software freshly updated (3.0, 2007)and the DTCs retrieved (P2106 Throttle Control Actuator Forced Limited Power and a P2135 Throttle Pedal Position switch A/B Voltage Correlation), we dove into the datastream and pulled up the three pots. The graph pattern on Sensors 2 and 3 should track together (although with slightly different voltages) and the trace on sensor 3 should be an inverted plot of the other two. While moving the throttle and watching the three pedal pot traces on the Genisys screen, I noticed that the three graphs were producing the right pattern sometimes and a dreadfully wrong pattern some other times.
The pedal assembly is about sixty bucks, and so I ordered one. Nothing changed. Found TSB 6-21-1 that listed a gaggle of codes including the ones we got. It said to replace the throttle body and reflash if the unit was built before 3/9/2005.
Well, this one was built a lot earlier than 3/9/05, so we put the updated throttle body on it and I had a graduate of mine re-flash it at the Ford store. The Five Hundred’s driver still had the same concern after a couple of days. This was getting interesting.
Connecting my $2000 four trace Interro PDA scope to the three pot wires, I wanted to see if I got a screwball set of traces like the Genisys was showing me. The traces were beautiful on screen, but with the scope connected the PCM wouldn’t allow the throttle body respond to the pedal movement. Disconnecting the scope, we got throttle actuation. Apparently the Interro had shorted the pot signal enough that the PCM didn’t trust what it was receiving. It was disgusting to me that I couldn’t depend on the $2500 Genisys OR the $2000 Interro PDA scope to help me with this one. I am now using a 4 Trace PICO scope, by the way.
After all that, it turned out to be a wire chafing on metal – caused by a vehicle accident from a year earlier!
Two More Bad Performers
In addition to the Monte Carlo, we encountered a 2004 Dodge Stratus with just under 70,000 miles and a cold misfire. The owner was out of town, so I’d have it for a few days.
We used the Interro (with a $3000 ignition system adapter) to paint the pattern. With a ragged #1 spark line and high snap patterns on the other three, the Stratus 2.4L got a fresh set of Champion Platinums and a verifying test drive. Everything seemed normal on the first couple of test drives, but we weren’t done with the Stratus: We just thought we were… More on that later.
The 148,000 mile Monte Carlo came to me via a phone call from one of our nursing instructors – she told me the transmission on her Chevy was shifting late and hard.
A short test drive was all it took to determine that the 2001 Monte Carlo was seriously underpowered – it took some pretty deep throttle to reach 30 mph and with that perceived load and speed, the transmission shifts were definitely late and hard, but the problem was an engine performance concern. A quick check of the transmission fluid showed it to be clean and full.
With the hood up on the Monte Carlo, we checked the engine vacuum – 18 inches idling with a steady 8 inches at about 2500 and a heavy and irregular induction backfire.
Fuel Pressure was healthy all the way through the problem range, hanging in at about 50 psi (normal for 8th VIN 1 – specs are higher if the 8th digit is K).
Our DTC scan with the Genisys gave a bevy of DTCs –
P0108B - MAP Circuit high voltage
P0128B ECT below thermostat regulating temp
P0404B EGR Open Position Performance
P0463C Fuel Level Sensor Circuit High Voltage (the ever popular fuel tank sending unit problem so common GM cars of this vintage)
P1404A EGR Closed Position Performance
Scoping the ignition system we saw a flat lining #4 leading to a spark plug inspection. The air filter looked good but the fuel filter had probably been in that same spot since the assembly plant and human lungs couldn’t shove any air through it.
We yanked the exhaust and it didn’t rev any better that way – that led us to check the ignition system. We put the exhaust back on.
Checking the plugs was tough. Those smooth and shiny Delco ceramics (why the heck to they do that?) can vulcanize to wire boots in a hot engine compartment like there are no tomorrows – I generally have to destroy the wires and put a new set on many of the 3800s I’ve done, and my students didn’t do much better on this one. Plugs and wires got rid of the induction backfire; the car ran smooth, but still wouldn’t pull your hat off.
Textbooks teach a troubleshooting procedure that focuses on the normality of exhaust temperature at various places. The idea is that the exhaust is supposed to be hotter coming out of the catalyst than it is going in, and just about everybody who has done any troubleshooting knows about that method. So you get an infrared temperature gun, start the car, raise it on a lift, and take readings.
We did. The exhaust going into the cat was 320 degrees, which is a little hot, but behind the catalyst it was reading 430 degrees. So what does that mean? Is the cat bad or good? Well, it runs like a bad cat, but what do we do with those temp readings? We learned from them – that test isn’t always right, so beware!!
With the header pipe and converter completely removed from the manifold, the engine still wanted to cut out on the lift, but that was the 4000 rpm rev limiter GM programmed in. The problem was that it sounded almost exactly like the engine had sounded the first time – had we been confused by a rev limiter and an induction backfire? A test drive with open exhaust went beautifully.
Monte got a universal cat that was actually a pretty good fit ($167) and the Chevy was back on the road, albeit still needing a thermostat and a fuel level sensor (see DTCs), but the customer didn’t want those concerns fixed on this trip.
Finishing The Stratus
The Stratus wasn’t finished – I drove it to lunch and found that the cold misfire had returned because #1 had a scorched the inside of spark plug wire boot, making a nice carbon track that tended to give the spark an easy path to ground that wasn’t through the center electrode. Oddly enough, the new Champion plug we put in #1 had a center electrode resistance of 57,000 ohms. The others read 17,000, 18,000, and 26,000. The old plugs read just over 5,000. I know Champion doesn’t like it when I mention measuring the center electrode, but Ford calls for it in their trouble shooting, so I do it on everything, especially when I’m chasing an odd concern. The Stratus got new wires and fresh set of Champion platinums for good measure.
Troubleshooting these days is almost impossible without sophisticated diagnostic equipment to gather data, but a real technician will learn to depend as much as possible on common sense whenever the high dollar boxes fall on their flat little faces and questionable troubleshooting procedures fail. Yanking the cat and driving the car turned out to be the test that made the grade on the Chevy, and a $10 ohmmeter smoked out a faulty new spark plug on the Stratus. A good head, good hands and steel wrenches are still the best tools out there. R.W.M.
From October 24, 2013's "Live from TST" webcast, "G" Jerry Truglia and Pierre Respaut utilize the Snap-ON MODIS, OTC Genisys Touch, Fluke 98, and Autoland Scope for Relative Compression. Check out the first of "Live from TST," live and 'hands on!'
With enhanced functionality, a faster operating system and a bigger, full-color touchscreen display, MODIS Ultra isn't just retooled. It's completely re-imagined. It's also more intuitive, with an 8" screen that can be navigated by touch or by its 4-way thumb pad. And you still have the sophistication and convenience of scanner, scope and exclusive Fast-track® expert information in one diagnostic tool. So you can move between jobs quicker and with more accuracy than ever before.
Professional technicians can maximize investment in new tool line with combination kits
Ingersoll Rand is rolling out four unique IQV20 Series™ cordless combination tool kits featuring products from the new cordless tool line. The four kits are designed to fit an array of applications in the garage bay. The impact wrench kit, IQV20-201 includes both the W7150 1/2″ high-torque cordless Impactool™ and the W5130 3/8″ mid-torque cordless Impactool, while the fastening kit, IQV20-203, includes the R3130 3/8″ cordless ratchet and 3/8″ Impactool. Two drill/driver and Impactool kits are also available. The IQV20-204 includes the W7150 and D5140 1/2″ cordless drill/driver, and the IQV20-202 includes the W5130 and D5140. Each kit comes with two batteries, charger and a rugged tool bag for storage.
IQV20 Series cordless tools have an integrated intelligent battery management system. This technology controls and coordinates power flow between the battery, switch and motor, and helps maximize system efficiency and runtime. The 20-volt lithium-ion battery platform allows for all tools in the line to run longer between charges — giving technicians the ability to complete a full shift on a single charge.
The battery interface offers the versatility to interchange both the 1.5 and 3.0 Ah batteries between tools. Product engineers designed the system so most tools in the series share the same batteries and chargers, allowing technicians have access to a freshly charged battery.
All tools are equipped with an all-metal drive train, delivering a wide torque range and high performance for a variety of applications. They are also built with an impact resistant housing, helping to protect against repeated drops and corrosive fluids and chemicals.
“As automotive technologies advance, service jobs get more complex and automotive technicians are forced to cover a larger scope of work in a limited amount of time,” said Nathan Schmid, marketing manager – vehicle services, Ingersoll Rand. “The Ingersoll Rand IQV20 Series offers professional technicians the tools they need to get the job done fast, every time. The new combo kits help technicians maximize their investment in the cordless line.”
For more information on the IQV20 Series combo kits, visit ingersollrandproducts.com/iqv20.
Have you ever stood peering into the engine compartment, scratching your head and wishing you could see inside the engine when faced with a drivability complaint? Wouldn't so many problems be easier to find if you could? Imagine being able to see exactly when the ignition event actually happened, or confirm that a valve that wasn't sealing as it should? How about verifying cam/crank synchronization without the need for a "known good" cam/crank sensor waveform or tearing the engine apart to access the physical timing marks?
You could do all this and more in minutes if you were using in-cylinder pressure testing as part of your diagnostic assault!
This test uses a pressure transducer and a digital storage oscilloscope (DSO) to monitor pressure changes in the cylinder while the engine is running. A transducer differs from a sensor in that the transducer is able to accurately measure the pressure while a sensor simply reacts to pressure change. The transducer converts the pressure measurements into a voltage signal that your scope can use to paint a picture of these changes on the scope's screen, bringing the idea of a traditional running compression test into the 21st century!
In this edition of The Trainer, we'll show you how what accessories you'll need and how to set up a scope to perform this test. We'll also show you the basic elements of the in-cylinder running pressure waveform, and what they have to tell you. After viewing this video, we're sure you'll see how valuable a technique this is and how it can save you hours of time in the shop!
The digital storage oscilloscope is a great diagnostic tool when used, but often the scope lays dormant because it takes too long to set up just to perform a simple check. Enter the AESWave UScope, a one-channel pocket-sized scope that boots up quickly and adds a level of convenience most big box scopes can't meet.
Yes, there are times you need that multi-channel scope but for those times you just want to take a fast look, consider the AESWave UScope.
For more info, log on to http://uscope.yourdiagnostictools.com/
The more they stay the same! The folks at AESWave (.com) recently shared this vintage video featuring founder Jorge Menchu discussing secondary waveform analysis. But it was filmed back when just a few guys were using scopes for drivability troubleshooting and before we had digital scopes that we could hold in our hand. The equipment might be old, but the lessons Jorge shares are still as valuable today. Check it out!
Then be sure to visit the AES website for more great resources and diagnostic tooling offers.
Curry’s Auto Service Highlights the Scientific Methods and Experienced
Teams Supporting the Services Performed on Hybrid Vehicles by Hybrid Shop
Gainesville, VA June 4, 2013 Curry’s Auto Service, one of the largest
independent auto service and repair shops in the Washington, DC, area,
highlights their official position about its proprietary and innovative
battery conditioning and rebuilding processes for hybrid vehicles on
behalf of The Hybrid Shop (THS) and Automotive Research and Design
THS and AR&D’s methodology, relating to servicing hybrid electric vehicle
(HEV) systems, is firmly rooted in sound technical methodologies, proven
testing and diagnostic processes (that reflect standards utilized by the
battery industry). In addition to upholding applicable industry
standards, AR&D’s 26 years of technical experience is focused on
supporting hybrid electric vehicle systems and battery technology. These
activities are led by AR&D Chief Technical Officer and recognized expert
in hybrid vehicle technology, Dr. Mark Quarto. Dr. Quarto is a hybrid
vehicle systems technologist and Electrical Engineer with over 28 years
of experience in hybrid and electric vehicle propulsion and energy
systems. Dr. Quarto’s professional and vast field experience includes
numerous technical contributions and management of research labs, service
engineering and practical experience resolving field product performance
concerns. In addition, Dr. Quarto is a patent holder in electric vehicle
drive systems, hardware and software developer, and a curriculum developer
and a technical instructor. His long standing professional memberships
include SAE (Society of Automotive Engineers) International and IEEE
(Institute of Electrical and Electronic Engineers), along with The
Scientific Research Society (Sigma Xi).
The THS team is composed of experienced technicians, professionally
trained and certified in hybrid battery conditioning. Our
environmentally-friendly and cost-effective solution to HEV battery
“conditioning” gives customers an alternative to costly battery
replacement. Through scientific methods and by appropriately cycling the
battery modules we can achieve up to 95% of its original energy
(capacity) and power that results in extending the overall service life
of the battery, thereby benefiting the customer.
It is the Electro-Chemical nature of a Nickel Metal Hydride (NiMH)
battery to experience apparent capacity loss (ACL), which can
significantly affect capacity and power during its service life. The
aggressiveness and severity of ACL is influenced by geographic area
(terrain), ambient temperature, drive cycle (highway vs. city vs.
blended), frequency in which a car is driven, and the individual drivers
style. Battery power can be affected by battery capacity and/or internal
resistance, which is also tested and measured as part of the conditioning
process. As a result, these batteries can lose capacity and power that
can eventually cause drivability issues including loss of horsepower,
torque, and reduced fuel economy. Therefore, capacity and/or power will
likely diminish in most NiMH battery cells over its service life. Similar
to Nickel Cadmium (NiCad) technology, this is a well-known phenomenon
with nickel-based batteries in the electro-chemical community; (many
consumers have experienced this occurrence with cell phones,
radio-controlled hobbies, power screwdriver tools, and other
electrical/electronic devices). However, applying nickel based
electro-chemical performance to HEV technology, is not well understood
today in the automotive community. In summary, for most nickel based
batteries to maintain proper balance, capacity, and power during its
service life the process of conditioning the battery cell (conditioning =
cycling with the proper process) will ensure that the battery will regain
(most of) its DESIGNED operating performance. It is a well-known fact
that NiMH can sustain 500+ cycles (conditioning) to regain its capacity
and power with the proviso that the batteries do not have electrolyte
loss, have not performed in sustained periods of internal or external
over-temperature conditions or been operated in an unbalanced or nearly
The Hybrid Shop at Curry’s Auto Service offers a 12-month/12,000 mile
warranty. Whenever the driver experiences reduced performance, a check
engine light (MIL), or, significant reduction in fuel economy, the
battery conditioning process should be considered. However, this process
should only occur after the basic vehicle systems have been eliminated as
the cause for the symptom (e.g. proper engine operation, tire pressure,
etc.). Based on the history of nickel based battery products, and how
it can affect vehicle performance, battery conditioning should be
considered as a maintenance procedure every 5-7 years (on average) to
restore the vehicle performance as close to the OEM’s stated vehicle
performance parameters as when the vehicle was purchased new if the
vehicle is having any performance or significant fuel economy issues.
The Hybrid Shop at Curry’s Auto Service can perform a comprehensive State
of Health (SOH) check for approximately $499, which applies toward
battery conditioning if needed. This SOH check includes:
€ A complete Vehicle Performance Inspection
€ Power and Energy Testing of battery modules
€ Testing the Electric Transmission (Motor Generator Unit) for electrical
and magnetic integrity, and aging (winding and insulation deterioration)
€ Testing Power Invertor (motor control) System wave form analysis and
the current control regulation system
€ DC to DC convertor output test (dc-dc component replaces traditional
belt driven alternator).
It is THS’ position that if a car is under warranty and the customer is
not experiencing any problems, the vehicle likely does not need service.
If the MIL illuminates and the car is under warranty the customer should
go back to the OEM dealer and secure a warranty repair. If the car is out
of warranty or a customer has an issue with a reduction of fuel economy,
performance or drivability, THS can often service the vehicle, if
necessary, for much less than a complete battery pack replacement. Also,
if the customer requests status of the battery pack SOH (capacity and
power), testing can be performed, documented, and resulting data provided
to the customer. For fleet customers (especially those with new vehicle
warranties that may be significantly less than the normal consumer
warranty period) THS offers a proactive predictive maintenance service
program. This program monitors the SOH of hybrid high voltage system
components, saving fleets costly down-time by trending and documenting
the overall condition of these systems at periodic service intervals.
It is the official position of THS and AR&D that a majority of the out of
warranty hybrid vehicle battery population can be serviced to restore
battery capacity/power utilizing the conditioning (or rebuilding) process
- as necessary - to extend the service life and performance of the hybrid
system. This service can save customers 60-70% when compared to the cost
of a new battery pack replacement and up to 50% when compared to
purchasing a rebuilt battery pack. This positions THS as a service
leader in Green Technology by reducing overall battery waste through a
proactive, experienced, scientific approach to service and maintenance.
About Curry’s Auto Service
Founded by Matt and Judy Curry in 1997, Curry¹s Auto Service was named
“2010 Top Shop” by Motor Age Magazine. In June 2010, Curry’s Auto Service
was chosen by the readers of Northern Virginia Magazine as “Best Auto
Repair Shop” in Northern Virginia. In addition, Curry’s has received the
highest AAA ratings in the country for customer satisfaction.
Headquartered in Gainesville, Virginia, Curry’s Auto Service is one of
the largest independent auto service and repair shops in the Washington,
DC, area, with nine locations in Northern Virginia and one in Maryland.
Curry’s services more than 4500 customers each month at its shops in
Alexandria, Arlington, Chantilly, Dulles, Fairfax City, Falls Church,
Gainesville, Gaithersburg and Great Falls/Reston. For more information,
please visit www.currysauto.com or follow us on Twitter and Facebook.
About Automotive Research and Design (AR&D)
Founded in 1987, AR&D is one of the leading automotive aftermarket
technology firms in the field supporting Hybrid and Electric Vehicle
Systems with specialized diagnostic equipment and credentialed technical
training. Other services and product offerings include project
management, consulting, instructor and student classroom materials and
custom curriculum development. As a leader in HEV Systems within the
automotive aftermarket, AR&D strives to provide products that support
scientifically-backed and technically sound solutions to educators, OEMs,
technicians, fleets, and other automotive professionals. The company
utilizes a wide range of partnerships, including but not limited to The
Hybrid Shop, SAE International, Educational Industries, and The
TurnaroundTour providing a full scope of products and services to the
aftermarket. For more information about AR&D please visit www.go2hev.com.
There is no question that a modern automotive labscope, in the hands of someone who is willing to learn how to use it, is a powerful diagnostic tool.
Many of the technicians we've met around the country tell us that they (or the shop) own a scope but are unsure of how to use it or when to use it. The answer to "when" is pretty simple. You can only get comfortable using any diagnostic tool or process by doing it a lot, and doing it first on cars you know are OK. As we've said in these pages many times over, troubleshooting problems is similar to that old game where you compare two pictures to one another, looking for the differences. If you look at lots of good "pictures" then when you see a bad one, it will stand right out!
How to use it is another story, and one we intend to try and help you with right now. In this month's "The Trainer" video, we'll show you the basic settings and how to choose the ranges you want dependent on the signal you intend to capture. We'll also show you some common testing procedures and how to connect your scope to perform them. And we'll also show you why these connections are made they way they are so you can apply that knowledge to future challenges on your own.
Special Preview of SureTrack™ Now Included with ProDemand™
With a subscription to Mitchell 1′s ProDemand™ repair information, you now have access to a preview of our newest product, SureTrack™ — the most comprehensive source of expert knowledge for professional technicians.
ProDemand provides the industry-leading OEM repair information you rely on every day to repair vehicles. SureTrack builds on that foundation, adding powerful diagnostic tools – just a click away, so there’s no need to search multiple databases.
Key benefits of SureTrack include access to real-world diagnostic information through a single lookup:
• Real-world fixes written by technicians
• Most commonly replaced parts based on real repair orders for the specific vehicle and diagnosis
• Guided component tests for each component and vehicle
• Waveform and graph library from actual on-vehicle tests
• TSBs and Recalls
• Life-line access to a community of expert technicians
This preview of SureTrack is available to all ProDemand subscribers at no additional cost. You will have access to all the features of SureTrack through September 2013 while we continue to enhance the product during the preview phase. The SureTrack product team is currently working to expand the powertrain information and in the coming months you’ll see the scope grow to include information on brakes, suspension, ABS, body electrical, HVAC, and airbag systems.
Click here to learn more about SureTrack.
Click here to learn more about ProDemand.
During the grand opening of Spanesi SpA training center and show room in Naperville, IL the Collision Repair Education foudation represented by Brandon Eckenrode, Director of Development and Clark Plucinski, Executive Director accepted a donation of a new Multi Bench 12 for the 2013 Makeover Grant Winner from Spanesi Managing Director, Timothy Morgan.
The mission of the Collision Repair Education Foundation is simple and straight-forward: "To secure donations that support philanthropic and collision repair education activities that promote and enhance career opportunities in the industry."
But the scope of our endeavor is enormous and complex. We're committed to partnering with generous donors to fuel the future of the collision industry with bold educational initiatives that will:
Foster and make accessible an educational environment of the highest quality for future collision repair technicians.
Promote a complement of highly-trained, qualified instructors.
Help educational institutions acquire state-of-the-art equipment, tools, and supplies.
Mold the collision repair technicians of tomorrow by enhancing educational opportunities for the collision students of today -- creating a link between collision repair schools and the businesses that will depend upon their students.
Provide the driving force to spearhead a new era of excellence in our industry.
Hello, I'm having a fit with My Jeep. It's a 2001 JGC Limited with a 4.0 inline 6.
I was pulling away from work about two weeks ago and it sputtered and died. Will restart and idle but can’t put in gear and drive of rev up. I got codes, Random misfire, cam and crank sensors, #1 and #3 coils. Replaced the sensors and coil with no luck, checked fuel psi at the rail and it is perfect at 45 psi. Thinking all that was left was the PCM, i ordered on and installed it today and it still won't start up and run. I'm out of ideas. Any help would be great.
First make sure the cam synchronizer hasn't locked up - with the cam sensor removed, does the cup spin when the engine turns? If so, set the cam sensor - line it up on zero TDC (compression, #1) and rotate the cam synchronizer until you can poke a toothpick through the sync housing AND the cup that rotates inside it.
Ok, well we set the cam sensor, but all that did was make it start better. It was 5 deg off. I hooked up the MODIS again and have 3 codes PO353, PO351, PO352 all are ignition coil primary circuit codes. Also was checking readings. At start up it starts and idles perfect! When you start to give it throttle the PCU goes from closed to open loop and starts to spit and sputter. If it doesn’t die it will start to idle like it is only running on a few cylinders. Also will run lean and the injectors are way open at about 7.5 pulse width rather then the 3.5 or so that they are at when it is idling smooth. Any help would be great.
What's the fuel pressure?
46 psi at the fuel rail.
If you have a scope function, dual trace the cam and crank sensors - the cam sensor should be making its switch halfway between two of the four tower clusters drawn by the crank sensor.
You need to see what you're losing when it sputters and pops - it's either starving for fuel (injector issues?) or it's firing out of time.
What would cause all three coils to throw the same codes though? Thanks for the help.
Check out the article on my website called "Scan Tools, O-Scopes, and Toothpicks" - I had a Jeep Cherokee throwing me ignition coil codes because of a cam sensor synchronization problem - it would drop companion cylinders and throw ignition coil codes and there was NOTHING wrong with the coils - period. Setting the cam sensor synchronizer with a scope the way I described fixed that one.
Just looked at the article again, so was your scan tool showing the synchronizer at 0 and it still ran bad? I put it at 0 today and it still won't throttle up. It was at +5.
thanks again. B.
Read the whole article - the scan tool readings were wrong - and I don't trust a Snap On scanner any more than the one I was using.
Just wanted to thank you for all your help and let you know what I found. Well the first thing I checked was the synchronizer cup. It did move a bit at that time but not to the point I thought the gear pin was sheered, so I moved on to everything else. Well I woke up Sat. And figured I would be working all day on the Jeep and maybe find the problem. So I start with the toothpick fix and got no results. Would start and idle great, but step on the gas and it would sputter,, backfire and die.
With the backfire I knew it still had to be a timing problem. I finally decided to pull the synchronizer and physically check the gear and pin. Well I found the problem finally after three weeks of over thinking the whole thing! The pin was not sheared, but was broke to the point that when I would rev it up it could move several degrees out of time. I went to our parts room and FREE roll pin installed it and set timing and boom! Running perfect!
Thanks again for everything.
Not too long ago, I got a call late in the evening from my youngest son’s girlfriend. Her Ford Explorer wouldn’t start, she said, and could I please come and help? What was I going to do, say no?
I grabbed a meter and some basic tools and drove over to see what the problem was. It didn’t take long to discover that the negative battery cable end had been replaced with one of those aftermarket clamp-style ends and it was spinning freely on the battery’s ground post, a classic case of voltage drop. The connection was enough to allow the lights to work, but as soon as the high current demand from the starter tried to make its way through, the connection gave up and went open. I removed the clamp and cleaned the connection, then reattached the cable to the battery and tightened it up. She started the truck right up and I told her to stop by the next day so I could make a more permanent repair and check out the rest of the system.
Did she listen? Of course, not…she’s a kid.
The next night I got another call from her, with the same complaint. Only this time the fault wasn’t a matter of voltage drop but of voltage period. When I arrived the battery only read 8.64 volts, nowhere near enough to start the Ford’s 4.0-liter engine. Heck, not enough to start my lawn mower’s engine! But why is there a problem with the battery now, just a day later, when the truck started fine last night and all during the day?
When you have a problem with the “no crank” or “slow crank”, you need to make sure you test both the battery and starting system to see where the culprit lies. And if the battery is weak, you need to know why. Is there a problem with excessive resistance in the cables, like I had the first night? Is the charging system doing its job to keep the battery healthy? Or did the battery just die of old age or neglect?
That’s the topic of this edition of The Trainer!
87-90 Cherokees – A Breed of Their Own
In 1989, after my employing dealership bought the Jeep franchise, I spent a lot of time in Jeep/Renault school. I was most familiar with the Ford engine control systems, and it seemed to me that the Renault/Jeep systems were a horse of a totally different color, and so I grappled with the oddities of it. In time, however, my perspective changed as I became more familiar with the product. The 87-90 Cherokee/Comanche isn’t like anything else out there, and the fuel system on these babies is a peculiar study, so let’s take a quick look at it.
The fuel system is fed through 5/16 rubber hoses connected with worm clamps to steel lines from a pump in the tank that should hold its familiar 30-40 psi for awhile with the engine shut down. If it doesn’t, pull the pump/sender assembly (you don’t have to pull the tank to do this) and tighten the hose clamps inside the tank. Voltage is fed to the pump through a ballast resistor from a relay over near the ignition coil and diagnostic connector. There’s also a familiar fuel pressure regulator on the fuel rail.
By the way, there are four relays in a line over there – The Fuel Pump Relay, the Power Latch Relay (which is controlled by one Engine Controller pin to feed power to another Engine Controller pin), the O2 Heater Relay, and the A/C relay.
The Cherokee/Comanche carries a multipoint sequential fuel system with a bell housing-mounted two wire VRS Crank Sensor (mounted on driver side at about10 o’clock), a distributor-mounted Hall Effect Cam Sensor for injector timing (50 percent duty cycle), an old GM style Manifold Absolute Pressure sensor, and Engine Coolant Temp sensor (up top and in the front) and an Intake Air Temp sensor (in the intake plenum behind the Throttle Body). There’s an adjustable Throttle Position sensor on the Throttle Body that is a dual function unit on Auto Trans equipped platforms, so it has two GM style weatherpack connectors, each with three wires, and the connectors are discretely designed so as not to transpose.
The Heated Oxygen Sensor looks like any other O2 sensor but is actually a titania unit that measures the temperature of the exhaust (cool is rich, hot is lean) and reads from 0 to 5 volts, with 5 volts lean and 0 volts rich, an arrangement that is antithetical to what we’re used to, but if you set up a scope and plot it on a graph, the pattern looks exactly like what you’re used to seeing, but remember, high O2 voltage reading indicates LEAN mixture, NOT RICH like everybody else’s system. More about that later.
The Bendix Engine Controller is mounted under the dash above the accelerator pedal at a peculiar angle and it is simple to remove (if you know where the screws are) but irritating to reinstall because the screw holes aren’t easy to find. That unit doesn’t generally need attention anyway, but be aware of it. The 16 ohm injectors are hard-grounded and fired with voltage pulses from the Engine Controller rather than ground pulses like we’re used to seeing on everything else.
Idle speed is controlled with a GM style four wire stepper motor, but I sure wouldn’t try a GM Idle Air Control on a Jeep. We had a special tool for checking the operation of the stepper motor at the dealer, but I have no idea where you could get one now. One set of windings in the IAC is connected to terminals A and B, and the other is connected to B and C. Make sure you compare the cone-shaped pintle on the end of the old one and the new one if you have to replace it… there are a couple of different pintle shapes used and the aftermarket people tend to foul this up sometimes.
The Throttle Body has an idle stop screw, but don’t jack around with that one. The idle air bleed screw is on the side of the Throttle Body behind an aluminum plug, and I haven’t seen one in recent years that hasn’t been tinkered with, but if it hasn’t been tinkered with, leave it alone. Cleaning the Throttle Body and IAC bypass passage is very easy to do on this engine and should be done at every oil change.
The PCV system consists of a grommet in the rear of the valve cover with a ¼ inch vacuum line connected to it. The grommet has a small hole that meters the vacuum. With the closure hose disconnected from the air cleaner and capped with your thumb, you should feel a slight vacuum with the engine running. If you feel pressure there and see crankcase steam, you’ll also have oil in the breather: Check the PCV grommet for clogging as well as the vacuum line and the hose nipple to which it connects.
The ignition system is beautiful in its design, with an e-core coil tidily mounted right on an ignition module that takes its orders from the Engine Controller. To check the operation of the ignition module and coil, just disconnect the two-wire weatherpack unit, connect your test light to power, and touch the probe to terminal B of the ignition module. The coil should fire each time you tap the terminal. The scope pattern it produces is unique, so get used to what a good one looks like.
The crank sensor that provides engine speed and crank position should read at least 480 millivolts AC while the engine is spinning with the starter, and if it doesn’t the Engine Controller might not respond to the signal. The connector is at the rear of the intake plenum, usually with a red wire and a white one. Measure this voltage with: A. The crank sensor disconnected, B. A cold engine, C. Your Digital Meter on 2000 mv, and D. Somebody spinning the engine. If the voltage is nonexistent, replace the sensor. If it’s a bit low, use a long screwdriver and gently bump it closer to the pulse ring. The crank pulse ring is a study in and of itself. On Auto Trans 4.0L Units, it has a lot of small windows separated from each other by very narrow metal vanes. At 120 degree intervals throughout the circle, it has a wide window and a wide vane. When it sees a wide window and vane, it knows that a cylinder is 90 degrees before TDC, and it uses the sync signal from the Cam Sensor in the distributor to determine which cylinder is coming up. If the sync signal fails (and sometimes it does), then the Engine Controller will simply pick a cylinder at random on startup, and on some starts it might run better than others. If something bends just one of the thin vanes inward, the Engine Controller will be confused and won’t fire the coil in time.
The spark plugs are easily accessible with the exception of #1, and the firing order is the familiar old straight six 1-5-3-6-2-4. A distributor sorts out the spark the old fashioned way, but the timing is not adjustable, primarily because the Hall Effect unit in the distributor has nothing to do with ignition. Put the distributor in with the rotor just passing the #1 firing post when the timing mark is on zero. Don’t, and you may have a road speed surge due to rotor alignment/timing advance issues.
One looming difficulty is the fact that the Bendix system’s datastream is totally inaccessible if you don’t have a Chrysler DRB II with a special adapter and cartridge, and to my knowledge, the aftermarket folks have never addressed the need. There is no Check Engine (MIL) light, and the orange Emission warning light that comes on after a certain amount of run time is tied to a special clock box under the dash that is dedicated to that purpose. The clock is resettable to kill the light if you know how to do it, but I won’t go into that here for lack of space.
There is no way to retrieve any trouble codes (which are worthless on this one anyway), and determining fuel trim numbers is a faraway dream without a scan tool. The diagnostic connector on the Cherokee/Comanche platform consists of two separate plugs mounted in a stamped steel plate over on the passenger side of the engine compartment near the Ignition Coil/Module assembly. The old MS1700 Renault tester we initially used would work, but it was so slow, squirrelly and clunky as to be non-usable. Be that as it may, there are multiplied thousands of these old vehicles (the giant majority are 4.0L) still running the road, and there are some ways you can track down problems on this generation, so if you’ve been buffaloed by some old Cherokees (pun intended, but it’s a stretch), maybe this article will be a good addition to your files.
First off, measure all the voltages on a properly running Cherokee or Comanche as soon as you can. This takes some creativity, but the sensors aren’t hard to find, and as technicians we have to be creative by our very nature, right?. You need to know what the sensors are reading with the engine running and not running, cold and hot. Those numbers will be your guide. Connect your o-scope to the ignition system on a good one and note the peculiar shape of the waveform – take a digital photo of it or store it if you can for future comparison.
One of the most common driveability problems is stalling, and if cleaning the throttle body and IAC passage doesn’t fix it, try having a look at the O2 sensor:
The one wrinkle here is that if the Oxygen sensor intermittently fails at low voltage (and it generally does), then an ECU in closed loop mode will attempt to correct to the lean side and cause the engine to stall. The O2 sensor heater is fired by a relay in a small bank of four over near the ignition coil and the diagnostic connector. So how do you find it if the sensor reads normally in the shop and you don’t have a DRBII? I connect a Digital Multimeter and drive it until the stalling occurs. Ideally, the customer may have noticed a pattern that you can follow to duplicate it. If the O2 voltage plummeted to the basement and stayed there shortly before the stall it generally means the O2 sensor is at fault, and sometimes the threads come out with the sensor, so be ready with your 18mm spark plug tap.
As with any system, the key to fixing this one is to get to know it. R.W.M.
Without a doubt, the use of a scope and pressure transducer to "see" running cylinder pressure is one of the greatest diagnostic tools to hit the bays in a long time. With minimal effort, a technician can grab a ton of information. This video is produced by Pico Automotive over in the UK but is a pretty good explanation of this method.
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