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02 Yukon p0300


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#1 joeg

 
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Posted 14 August 2007 - 01:14 PM

Working on an 02 Yukon, 5.3l. Has steady miss, #7 and 8 dropping on cylinder balance. P0300 is only code that sets. Both cyls have spark, fuel, injectors are firing, good compression. #7 smooths out at higher rpm but 8 is dead. Checked rockers and pushrods, swapped coils and injectors to different cys. and miss stays with 7 and 8. We are a Ford dealer so dont see to many of these. Any help is certainly appreciated. any-help.gif
Joe Gullifer
Service Manager

#2 trueblueFS

 
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Posted 14 August 2007 - 09:26 PM

QUOTE (joeg @ Aug 14 2007, 02:14 PM) <{POST_SNAPBACK}>
Working on an 02 Yukon, 5.3l. Has steady miss, #7 and 8 dropping on cylinder balance. P0300 is only code that sets. Both cyls have spark, fuel, injectors are firing, good compression. #7 smooths out at higher rpm but 8 is dead. Checked rockers and pushrods, swapped coils and injectors to different cys. and miss stays with 7 and 8. We are a Ford dealer so dont see to many of these. Any help is certainly appreciated. any-help.gif

Its a possibilty you might have a vacuum leak causing those two cylinders to missfire. The intake manifold gaskets are known to leak & cause rough running & missfire codes on the 5.3 engine.

#3 joeg

 
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Posted 16 August 2007 - 02:13 PM

Broken exhaust valve spring!
Joe Gullifer
Service Manager




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