Suburban 2500 6.0 Issues

I'll tell you how I figured out where my misfires were coming from. At idle (and during one of the misfire fits), I simply unplugged each coil's electrical connector. If you unplug one of them (or maybe two, such as myself) and the idle doesn't change or get worse, then that is the dead coil. To verify, I swapped it to another cylinder and tried again with the same results. My problems started off with a PO300 and eventually, as the coil died, it would actually throw a code for a certain cylinder.

Once you narrow down which one it is and replace it with a good AC Delco part, I can assure you that it won't give you any more troubles for quite some time. I let my truck sit for two months 2 years ago because I, like you, was so frustrated trying to track it down. Again, I would bet money on it being as simple as a dead coil. At least this motor will never shoot out a spark plug like a 5.4 or the V10 :D


Are your only codes the PO300? The only reason I ask is the LS series motors are prone to leaking intake gaskets after a while. If it says anything about Bank 1, Bank 2 lean, then that would solve it that and possibly the misfire. I wouldn't think the intake leak would cause a misfire, but it certainly could if they're bad enough. This issue isn't going to be anything major, they're pretty easy to work on and actually fairly simplistic.
 
Just a little update..

Stared checking coil wires again and found when I shook one the running condition changed. Replaced the wire, so far so good, but it has behaved for a while before.

Not sure if that's the issue but we will see... I'm considering picking up a setof accel coils and just replacing them all if the problem shows back up...
 
Not bad. Looks like the Accel coils are about the same price as factory ones. Get good quality plug wires too, I (very suprising to me) had a set of wires go bad just from letting the truck sit. Swapped them for a new set and never had another problem.

I've also never had good luck with any plug other than an NGK or AC Delco in these motors. FWIW. I ran a set of Bosch plugs and lost about 2mpg, no clue why.

I hope that gets you going though. I have the feeling you'll love that thing once you get all the little kinks ironed out.
 
Ran a can of sea foam through the burb today, ran pretty strong and no warning lights... From what I understand it sat a lot so I wondered if the issue could have been injector related as well... So far so good.. Had a random Trimble or two today, I may have fixed it or it could just be in one of it's behavior cycles. What this does confirm is its an electrical component failure and nothing more serious. A compression issue, clogged cat or valve issue would be more consistent.

If it comes back i hate to replace coils or injectors or ECM, it's going to be one of those three, blindly... Are there more dynamic tests a shop or dealer could do to narrow it down?
 
For some reason, with the stock operating system in use I've noticed several of the trucks, or anything using the Gen III motor for that matter, will sometimes have a random tremble at idle. My truck did, wasn't a misfire and wasn't fuel pressure related. If it turns out to be the injector(s), I have two different sets of stocks ones out in my shop IIRC. I'll never need them.

If I could hook to it with my laptop and data log it, I may be able to track down a spark issue. I know I would be able to see an injector problem with it. I wouldn't think the ECM would go bad, but if so, a stock reflash from a dealer should be able to solve it. If it did require a different ECM then you could get one used (fairly cheap) and have that one flashed with the proper operating system and such.
 
NCJeepin said:
Ran a can of sea foam through the burb today, ran pretty strong and no warning lights... From what I understand it sat a lot so I wondered if the issue could have been injector related as well... So far so good.. Had a random Trimble or two today, I may have fixed it or it could just be in one of it's behavior cycles. What this does confirm is its an electrical component failure and nothing more serious. A compression issue, clogged cat or valve issue would be more consistent.

If it comes back i hate to replace coils or injectors or ECM, it's going to be one of those three, blindly... Are there more dynamic tests a shop or dealer could do to narrow it down?
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Maybe I'm an idiot but I still think I'd find a good dealer with a gm scanner and let them hook it up. I wouldn't let them do work and I'd get the diagnostic price quote up front but I'd probablly go with a relearn and flash. It may not fix the issue at all but you should easily be able to cheaply rule those out. My understanding is those are $25 items or less at a reputable dealer.
 
Started to run shitty again, and this time its worse. Headed to the shop in the morning, its my trusted local shop they said they have all the computer equipment to work on this thing and he seems to think its going to be a simple issue. Looking forward to actually enjoying it.... Yesterday I estimated 6mpgs, if its starts behaving I'm pretty sure I'll hang on to it despite my wife's objections to how hard it is to drive.
 
Really hope you get it squared away. So far I'm loving my new one with the 8.1. Once I get my Ram sold I'm getting mine fully serviced to help avoid issues like this.
 
Results from the repair shop....

2 loose spark plugs, 2 burnt spark plug wires shorting out to the exhaust, and then a broken exhaust pipe 6" down from the manifold flange.

$165 bucks later and it will be ready for me to pick up this afternoon.... I've never had a come back from this shop, so it looks like I should be good to go, and can finally enjoy this vehicle!!!

Thanks for all the help, I'll keep y'all posted.

Bruce
 
Just picked it up.. it is NOTHING like it was.. There were some major issues going on with those deficiencies.

I had no idea this 6.0 put out so much power....
 
Lol sounds like a well invested $168. For gremlins like those I never hesitate to pay a few bucks to let someone else whose seen a couple hundred and has the right scanner look at it. Glad it worked out.
 
:D I love a 6.0! I've never driven a stock one though....


Glad to hear you got it all taken care of and it was something simple!
 
Final Update.

All is good in 6.0 world... Threw a cold air intake on it saturday, she runs out nice... Still not 100% the vehicle is for me, but atleast its running out nice now and I can get some good use out of it... I really appreciate all the help!
 
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