My 99 GMC truck needs a miracle

[leolkfrm]

compression test will help eliminate a mechanical part breakdown, rings valves etc

[mudseeker]

instead of clearing the code you should have saved the freeze frame data when they were set. it could be anything, the freeze frame would have helped pinpoint it.

[Sneakysportsman]

Sonds like the exhaust lobes on the cam going down. Or the lifters collapsing.

[Redrocket1045]

Originally Posted by Sneakysportsman

Sonds like the exhaust lobes on the cam going down. Or the lifters collapsing.

Wouldn't the engine miss with a bad lobe/lifter? Once the engine has undergone its 30 second cycle - it will run almost like normal. It idles at around 550(which is not normal) and accelerates fine(without a load). When I gun the engine - I notice some - not a lot - but some black smoke out the tailpipe. As stated before - if I shut off the engine and restart - I have to repeat the process again or she just won't idle(run at 2000 rpms for about 30 seconds).

[bradrhale]

wont miss if this is an exhaust lifter. 550 rpms is not that bad. my 00 idled around 600. this was after i replaced the TPS. it did idle around 1200. have you cleaned any carbon deposits out of the TB?? could be causing a rich mixture, the black smoke, and once you have cleared her throat out, she would start running correctly. might also check the vacuum theory as well just for giggles.

[Redrocket1045]

Originally Posted by bradrhale

wont miss if this is an exhaust lifter. 550 rpms is not that bad. my 00 idled around 600. this was after i replaced the TPS. it did idle around 1200. have you cleaned any carbon deposits out of the TB?? could be causing a rich mixture, the black smoke, and once you have cleared her throat out, she would start running correctly. might also check the vacuum theory as well just for giggles.

Thanks. Yea, I checked the TB and it's clean. I'm going to check out the vacuum theory next. I'll post the outcome later.

[Sneakysportsman]

Did you check the fuel pressure regulator?

[Redrocket1045]

Originally Posted by Sneakysportsman

Did you check the fuel pressure regulator?

Yea, the fuel pressure regulator and the fuel pump are fine.

[Redrocket1045]

Originally Posted by Redrocket1045

Thanks. Yea, I checked the TB and it's clean. I'm going to check out the vacuum theory next. I'll post the outcome later.

Checked out the vacuum to the booster and there's plenty. If I crimp the hose with some vice grips the idle comes up a tad(about 100 rpm) but it still misses upon start and I have to fast idle at 2000 rpms for approximately 30 seconds to get it to run half decent. This is really pi**ing me off.

[mudseeker]

like i stated before, we need the freeze frame data to make an educated guess at what the problem might be. it could be as simple as a bad EGR. an EGR that is open at idle can cause a stumble/stall condition. it needs to be put on a tech2 and components tested. i've had an EGR that would go wide open when the computer commanded anything more than 40%. requested values and actual values need to be compared to find your problem.