Random Misfire

Dieseltruckin2001 · April 3, 2008

I have a 2004 z71 1500 with 5.3l. Cold air intake and exhaust. I have rough idle and it will spit and sputter around 2000-2500rpm. I have checked as best I can for any intake leaks, cleaned the MAF and put new plug wires on yesterday. I am going to get new plugs as soon as I decide which ones would be best. Every once in a while I get a check engine light. Take it to my local speed shop and the code reads "random misfire." I have talked to everyone I could minus the dealer and haven't had anything help. Had a TB spacer on, took it off, no change. I do not where all the vacume lines are that I should be checking so maybe somethin there. Any help would be appreciated.

cwh · April 4, 2008

I have a 2004 z71 1500 with 5.3l. Cold air intake and exhaust. I have rough idle and it will spit and sputter around 2000-2500rpm. I have checked as best I can for any intake leaks, cleaned the MAF and put new plug wires on yesterday. I am going to get new plugs as soon as I decide which ones would be best. Every once in a while I get a check engine light. Take it to my local speed shop and the code reads "random misfire." I have talked to everyone I could minus the dealer and haven't had anything help. Had a TB spacer on, took it off, no change. I do not where all the vacume lines are that I should be checking so maybe somethin there. Any help would be appreciated.

You didn't mention the fuel filter. When was the last time you replaced it. I had similar symptoms on a '98 Tahoe that I owned a few years ago. Idled rough and sputtered and lost power in mid rpm range. Changed the filter and it ran like a top.

Chris

pennzoil29 · April 4, 2008

Ditto on the fuel filter. To many of us over look this item. I usually change mine every 10k.

Dieseltruckin2001 · April 4, 2008

Well, I thought about that. Went to the parts store to get one and it showed up as non-servicable??? They told me the filter is on the pump??? This sounds strange to me but then again this is my first gas motor, lol. Anyway, aside from that, I put new plugs in it last night and unplugged the battery and let set over night. Hooked it up this mornin and so far its runnin smooth!!!!!! Engine light went away and everything. Now that I said that I'll prob go get in it and it will mis like crazy, LOL!!!!!! So, I'll cross my fingers. But I would like any info on this fuel filter though. Thanks for the suggestions!!!

Draenor · April 4, 2008

Thats correct starting in '04 the fuel filter and pump are all in one, in the tank. Non-serviceable means your gonna have to replace the entire unit. Have you cleaned the TB? Sometimes it gets gummed up and you get a bit of rough idle. I would also keep the spacer off, as it does nothing. Make sure the TB gasket is not worn or torn. As for the mis-fire your going to need a Tech2 to scan. You can also take off each spark plug wire when the mis-fire or hessitation occurs and see if a difference is made.

cwh · April 4, 2008

Thats correct starting in '04 the fuel filter and pump are all in one, in the tank. Non-serviceable means your gonna have to replace the entire unit. Have you cleaned the TB? Sometimes it gets gummed up and you get a bit of rough idle. I would also keep the spacer off, as it does nothing. Make sure the TB gasket is not worn or torn. As for the mis-fire your going to need a Tech2 to scan. You can also take off each spark plug wire when the mis-fire or hessitation occurs and see if a difference is made.

I had an '01 GMC K2500HD with 8.1/ally combo. I bought and installed a set of the bosch platinum 4 plugs. The truck never did run right with those plugs. When I pulled them after less than 6 months they were all carboned and gummed up. I installed a set of AC delcos and never had another problem.