Multiple Cylinder misfire

buttaluv · 01-16-2008, 08:41 AM

My truck recently started acting up, a couple of times, when the motor was cold, it would not want to keep running, even dying a couple of times. After running for awhile it would run ok, (I have never thought it idled all that well). I took it in to have it checked out and it had "multiple cylinder misfire" I guess 4 of 8 cylinders must have misfired at the same time. I did tune it up this summer, plugs, wires, etc..

oh yeah it's a
99 GMC
4x4 4.8 liter auto.

mudseeker · 01-16-2008, 01:47 PM

who did you take it to? did they tell you the specific code? the codes would help out alot.

gmtech · 01-16-2008, 09:26 PM

Alot of intakes leaking vacuum when they are cold spray some carb cleaner around the base of the plastic intake on a cold moring to see if the idle changes if so need to replace the gskts

o3shortbed · 01-17-2008, 06:06 AM

my former bosses truck (99 chevy 4wd 5.3) he had the same code turns out his #7 coil pack was misfiring. he replaced 3 of them to find it.

nmw75 · 01-17-2008, 08:03 AM

I'm going thru a "Random Misfire" problem right now too. Narrowed it down to a faulty fuel injector. Installing a new one tonight & hopefully it fixes the problem.

I'm lucky enough to have a friend that can borrow a GM code reader / diagnostic computer. We could watch each cylinder as it fired or in the case of cylinder #1 didnt fire. The coil was working so that led us to the injector.

Finding a cause of a misfire is not an easy job!

01-16-2008, 01:47 PM	#2
mudseeker Senior Moderator Join Date: Feb 2006 Location: michigan Posts: 6,374	who did you take it to? did they tell you the specific code? the codes would help out alot. __________________ i'd rather be hunting

01-17-2008, 08:03 AM	#5
nmw75 Full Member Join Date: Jan 2008 Location: Maine Posts: 21	I'm going thru a "Random Misfire" problem right now too. Narrowed it down to a faulty fuel injector. Installing a new one tonight & hopefully it fixes the problem. I'm lucky enough to have a friend that can borrow a GM code reader / diagnostic computer. We could watch each cylinder as it fired or in the case of cylinder #1 didnt fire. The coil was working so that led us to the injector. Finding a cause of a misfire is not an easy job! __________________

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01-16-2008, 08:41 AM	#1
buttaluv Junior Member Join Date: Oct 2007 Posts: 9	Multiple Cylinder misfire My truck recently started acting up, a couple of times, when the motor was cold, it would not want to keep running, even dying a couple of times. After running for awhile it would run ok, (I have never thought it idled all that well). I took it in to have it checked out and it had "multiple cylinder misfire" I guess 4 of 8 cylinders must have misfired at the same time. I did tune it up this summer, plugs, wires, etc.. oh yeah it's a 99 GMC 4x4 4.8 liter auto.

01-16-2008, 09:26 PM	#3
gmtech Senior Member Join Date: Dec 2005 Location: farmville Va Posts: 348	Alot of intakes leaking vacuum when they are cold spray some carb cleaner around the base of the plastic intake on a cold moring to see if the idle changes if so need to replace the gskts

01-17-2008, 06:06 AM	#4
o3shortbed Senior Member Join Date: Jan 2008 Location: L-burg KY Posts: 334	my former bosses truck (99 chevy 4wd 5.3) he had the same code turns out his #7 coil pack was misfiring. he replaced 3 of them to find it.