2000 GMC Sierra Code P0300

LAVAJACK

MEMBER
2000 GMC SIERRA
6.0L
V8
4WD
AUTOMATIC
139,500 MILES

Misfire on 4 of the 8 cylinders. The 4 on the drivers side the coils, plugs and wires are fine. Had to replace the wires going to the coils something chewed through or cut to one of the coils that is when I found out only running on the passenger 4 cylinders. Wires all fine, what do you think maybe blown? Thank you in advance. Dale

3 Replies

HMAC300

MECHANIC
48,601 POSTS

Misfires are hard to find and mostly should be left to a pro so you don' put unnecessary parts on it. This should be scanned for codes and freeze frame applied because it may be an engine sensor causing it or low fuel pressure. Fuel pressure should be 55-62 psi with key on only. Auto parts rent gauge that can do it as well. It should meet minimum pressure

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Thursday, November 5th, 2015 AT 6:12 AM

LAVAJACK

MEMBER
2 POSTS

Not fuel problem not getting spark to the drivers side of the engine. The coils are fine wires are fine and tested looking through all wires to find a break cannot find any, thought someone may have came across this problem.

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Thursday, November 5th, 2015 AT 6:31 AM

HMAC300

MECHANIC
48,601 POSTS

Unfortunately this can be an ecm problem but until it is scanned and checks for resistance of wires from coils to wires is about the only way. Due to the positioning of pcm it can get water in it and destroy it. And truck can have furl pressure but not enough also if engine has been replaced prior to this then the cam and crank sensor have to be told as they will be still using old motor. You might takethis to a local pro and try the crank relearn to put cam and crank sensors in tune as a lot of guys seem to be this is the problem. It won't allow the coils to fire correctly. That seems to be what other techs are saying in tip section.

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Thursday, November 5th, 2015 AT 7:21 AM