Is anyone else experiencing "cylinder 7 misfire detected?"
80

Asked by paulb Jul 15, 2009 at 09:43 PM about the 2004 GMC Yukon SLT 4WD

Question type: Maintenance & Repair

After going through the normal checks - plugs, wires, coil packs - a new fuel injector in no. 7 cleared the code.  That was in May.  It is now July and the problem has returned.  Same cylinder, same problem.  Upon further inspection of the injectors, I found they are comtaminated with what looks like rust.  Ironically, there are a couple of Technical Service Bullitins out that describe what I am seeing.  Unfortunately, the TSB's only contain summaries.  Does anyone have any details they can share on a fix for this?

Oh, and another thing.  There is no exrenal fuel filter on this truck.  I happen to own the GM service manual and it shows where it is and how to replace it, but it is not there.  In the description of the fuel system, it says there is a filter in the fuel sending unit assembly inside the tank and is non-servicable.

2 Answers
20,115

Mike answered 15 years ago

You obviously at this point know what the problem is ( Rust ) - I would guess the fuel line enters the fuel rail around #7 cylinder hence it getting plugged Just a guess there :) Pull the tank my friend - Depending on the mileage do a PUMP and Filter screen ( No Cash then the screen is replaceable ) - Flush the tank and all lines INCLUDING the injector rail and injector screens ( they clean pretty easily with carb cleaner ) Reassemble ... Good Luck

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80

paulb answered 15 years ago

Thanks for the response. That's what I was afraid I'd need to do. probably a good idea to flush the entire system out. Can't imagine where the rust (if that's what it is) is coming from since most of the system is plastic. Thanks again.

Mark helpful

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