QuestionQUESTION: I have a 2004 GMC savanna full size extended van with a 6.0 liter v-8 engine with mileage at 56,000. The van started to idle rough and stalled. After reading the codes it came up as a P0101 and a P0300. I replaced the Mass air flow sensor, checked for vacuum leaks, and replaced spark plugs. The van starts after clearing the codes but once the throttle is pressed further than 1/3 of the way the van starts to idle ROUGH again almost stalling. I have noticed that parking the van with the rear of the vehicle elevated it seems to start and idle fine. Any help would be greatly appreciated.
thanks pete
ANSWER: Hi
Could you PLEASE try to get the PCM scanned again, and let me know which exact cylinders are miss firing?
The mechanic SHOULD be able to observe the data and let you know whick one(s) are missing.
Thanks
Pawl
---------- FOLLOW-UP ----------
QUESTION: Pawl
I got the van to start idling bad. Then I scanned the codes and turned up a P0101, P0304, P0300 codes. I did notice the cylinder 4 plug was saturated with fuel when I changed the spark plugs. Also when the van is idling rough a large amount of carbon smoke and the smell of unburned fuel can be detected at the tail pipe.
Thanks,
Pete
ANSWER: Hi Pete
It REALLY sounds like you MAY possabally have a bad injector on the #4 cylinder.
The p0304 would verify that it is the #4 cyl.
You could check it with a noid light, making sure it blinks and is not on steady.
If it is on steady, the injector harness is shorted to (-) ground OR the PCM is keeping it grounded. That would be WORST case scenario.
I would more likely suspect a bad injector.
I Hope this helps.
Please follow post back, if needed.
Pawl
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QUESTION: Hi Pawl
I finally got around to changing out the fuel injectors. I did all 8. I started the vehicle and I have the same problem again. I checked to see if maybe the ignition coil or wires were bad... no luck. Is there anything else i should check that may cause this type of problem.
Thanks Pete
AnswerHi Pete
Lets get back to basics and original post.
A Misfire CAN be caused by
Fuel system
Ignition system
Engine Mechanical
Your original post stated if it is elevated it runs OK.. does this still hold true? Is fuel level OK?
If so I would check fuel pressure....55-62 psi
SHOULD hold when key turned off....
If not the feul tank unit is at fault.
Also on the passenger side of engine the wire harness comes around the back of engine from drivers side to passenger side.
with engine running, wiggle and tug on the harness not too hard, but a hefty tug and wiggle the whole harness from back to front.
IF it acts up I would HIGHLY suspect the connector that breaks off and goes to the coils for that side.
Also is it JUST the #4 cylinder still...
If it is that even side (2, 4, 6 & 8) I would also HIGHLY suspect the front oxygen sensor..It CAN cause this.
Since you've eliminated other fuel and ignition...ONLY item left after this would be Engine mechanical...
Run a compression test on all cylinders.
It COULD be the cam or a lifter...
Please follow back post
Pawl
