1990 Chevy Suburban idle/accleration problems

[SoCalSlaughter]

Hey guys, i have a 1990 Chevy Suburban with the 5.7 350 TBI, and I'm about to pull my hair out with this truck. Its been running bad like this for almost a year. It has a really hard time accelerating from a stop and when its warmed up the idle wants to shoot to almost 2,000 in P. I also noticed while Im driving the IAC will whistle like a turbo when I let off the gas and at a idle I can hear it sucking in a bunch of air. Sometimes I get a engine light but it always read "Lean". Sometimes when its cold it runs like a camp, like nothing is wrong, but after awhile of coming to stop signs it starts to do it again. Most of the motor is new and new sensors and ignition. Replaced intake manifold gaskets, egr gasket, valve cover gaskets. I noticed that the PCV valve vibrates very quickly even when I pull it out of the valve cover still connected to the TBI. And the timing is dead on. Since I've had the truck (Got it with 113,000. now at 141,000) Ive rebuild the TBI, intake manifold gaskets, new distributor, preformance ignition system, all new gaskets, all new sensors, fuel filter. Im thinking dead cylinder or burnt valve.

[cableguy0]

You need to check for vacuum leaks first and foremost. Where is your timing set at? Was it set with the est wire disconnected? If you hear an obvious whistle there has to be a vacuum leak somewhere. Lean codes also indicate a vacuum leak. It could be a lack of fuel but it wouldnt run better cold if it was fuel flow. Im gonna bet you have a massive vacuum leak somewhere and while the engine is in closed loop for cold start up the extra fuel being dumped for warm up is overcoming the vacuum leak.

[SoCalSlaughter]

The the brown wire is disconnected and I set then timing to 0, the advance a few. And all the vacuum likes are new. Have a vacuum gauge hooked up to it and at idle in gear it reads about 14psi. And the whistle is coming from the IAC. When i stick my finger in the valley where the IAC pulls air, the whistle stops.

[cableguy0]

Get a can of carburetor cleaner. And spray around the intake and throttle body while the engine is running. The engine will rev if you hit a leak. at that point try to pinpoint where its leaking and fix it. After you do that. Put the timing back at 0. Then unhook the battery and leave the truck sit for an hour or so to make the computer lose its memory. hook the battery up and restart the truck. Remember just because a component is new doesnt mean its actually working. Are you throwing any codes and what are they? Vacuum should be closer to 20 inches but we will tackle that afterward. The other thing to do would be a compression test to make sure that the engine is mechanically sound.

[SoCalSlaughter]

Ive reset the ECU a few times trying to set the timing back. But will still run the same. And I've replaced the TBI gasket and manifold gasket and sprayed them down and still nothing. And the only codes Ive been throwing is the "Lean" code. Usally comes on after ive been driving. park it for about 20 minutes and start it up again it comes on and goes off after I start to drive.

[cableguy0]

What is the code number? Is it an o2 code? A bad oxygen sensor can also cause some of your issues.