Can’t figure out this truck at work! Here is some background on the truck. Its a 01 Suburban 2500 Series with the 6.0L. I can’t get rid of this misfire and its driving me crazy. Its was flashing for about two weeks and someone finally brought the truck to the shop. Now it was Cyl#8 misfire. Since it has 78K on it I replaced all the plugs and wires. Now I'm getting a random misfire. Cylinder #7and 8 has a bad miss now. I switched the COP with no help. I ohmed out the injectors and all are 11.6 Ohms. I put some fuel injector cleaner in the tank and went for a drive on the highway and still I’m getting a misfire after the highway run there was some misfires on cylinder #1 and 4 but mostly 7 and 8. I’m only getting a random misfire code none are setting a specific cylinder code but I’m just looking at my operation data on my scanner. Now I’m thinking either got a couple bad plugs or my gap is off. They are iridium plugs and you aren’t supposed to change the gap but after the first set of misfires I changed the gap to factory gap of .060 with no change.

Am I missing something here? I guess I'll put a fuel pressure gauge on it tomorrow to make sure its getting the proper amount. Any ideas on what i could do next. I was just talking with my snap-on guy today and he was talking about the new Vantage Pro seems like an awesome program I wish I could graph and view fuel pressure, injectors, and spark. I’m think about bringing in my laptop and SCT program and using that haha.

Sorry for the long post try to be a thorough as possible.

John

 

Yes, this is a Ford site. The Suburban would be a GM/Chevy.

 

i'll try to help even though its not a ford.
have you ever had the dexcool coolant flushed? have the pos plastic intake gaskets ever been changed yet? what was the gap at before you put it back to .060? what kind of plugs did you use? could be the whole entire egr system, because the 6.0 had a junk system on it. there are too many possibilities to list for that engine. the chevrolet 6.0 was junk IMO.

 

why are you using iridium plugs? they usually burn too hot for the typical engine.

 

Thanks for the info now I’ll go to chevytalk.com haha. Just thought there might be a GM tech or someone with some useful info - you know that’s possible even on a ford site.

Yep the coolant has been flushed. Haven’t checked the intake manifold yet Ill check for leaks tomorrow. I put AC Delco Iridium plugs in there and thats what came out. I called up Carquest and thats what they sent. The plugs out of the box were gapped at .040. This truck has done a lot of idling and it never really leaves the city since its a deputy chiefs truck so Ill look into the EGR system. I’ll pull the EGR valve to see how gummed up it is.

Thats what came out of the truck.

 

Yea, looks like you lucked out!

 

No no no

Their a healthy fine wire plug , small improvement over platinum is all.

 

What code is it throwing, #8 misfire?

I bet it's a COP. Try replacing them with new ones. Depending on the miles this may improve the overall performance also even if it doesn't fix the problem.

Try posting on a GM / Chevy truck site. They should be able to help better.