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Congratulations to our June winner!

 

Congratulations to Ronnie Raines, our June Motor Age Training/Federated Auto Parts "ASE Question of the Month" winner. June's question was:

 

A V8-equipped vehicle is in with a complaint of rough performance and low power. The technician checks the scan data and notices that the total fuel trim for bank 1 is a positive correction while the total fuel trim for bank 2 is a negative correction. Which of the following statements is correct about this MAF-equipped engine?

 

A.   This is an indication of a leaking intake manifold gasket on bank 2.

B.    This is an indication of a restricted exhaust on bank 2.

C.    This is an indication of unmetered air on bank 2.

D.   This is an indication of a leaking injector on bank 2.

 

You’re correct if you answered B!

 

All answers but B are incorrect because they refer to problems on one bank only. None of them explain the positive fuel trim correction experienced by bank 1. However, on a MAF engine using two separate catalytic converters, it is possible to get opposite corrections between banks when only one of the converters is restricted. The MAF measures, and reports, the total mass of air entering the engine. But with one side restricted, one side of the engine is getting more air than the other. The side with more air will run lean and generate positive corrections to compensate while the restricted side will have less air, run rich, and require negative trim correction.


Try your hand at July's question and be sure to enter the drawing sponsored by Federated!

 

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