crash813

Well, after over a month, I finally found my issue..... one plug had a cracked insulator. Plugs were only 6 months old and were factory Denso's. Strangest part was it never sounded like just one cylinder misfiring. But once I replaced it, it was good to go.

For your issues GMC, I would double check your TPS and stop screw settings. Its literally fractions of a mm that changes closed, to partially open, to WOT on that thing. Make sure its setup correctly. It took me awhile to get it setup right and I had to take the TB off to do it. I would also look at the plugs you took out. Do they look like they were burning rich or lean? Lean I would keep chasing air getting in the system somewhere since it sounds like the fuel system is working correctly. Rich and I'd check you air filter and afm. You might also want to check your o2 sensor since its reading that in partial throttle situations and not predefined maps based on afm. Good luck either way.

crash813

Almost forgot, I know it sounds crazy but double check your grounds. Factory grounds are usually pretty stingy to begin with but after 20+ years, they can fail at intermittent times and create all kinds of gremlins. I always upgrade mine now.

gmc

Thanks for the responses. I think I finally found something. I disconnected the EGR and it runs great. Everything tested good, but something must be sticking or leaking in the EGR system. I plan to dig a little deeper this weekend.

chukarhunt

iTrader: (1)

I had just posted to check your AFM, but you already did that, so nevermind lol. My computer has been sending me an EGR code for months now, but the truck runs great. Strange how EGR can affect how an engine runs. I know the EGR only works when at part throttle, so it may be something related to the TPS, but it sounds like you already have that dialed in too. Good Luck! Sorry, I don't know much about the EGR, I just took mine off.