Chuggle -- more info -- no ideas?

[sevie8]

Still working on this -- HELP, Chevy guys! No trouble codes set. On hot start only, I have a surge and then stumble on move off. Also have it on light throttle cruise. After increased throttle it doesn't occur. Things done -- new fuel filter, PCV valve, distributor cap, rotor and spark plugs. Timing set to specs. EGR valve clean, holds suction, EGR solenoid works and holds suction. Swapped in old O2 sensor (which worked fine) and problem still there. NO vacuum leaks found.

Disconnecting the IAC stops the problem, but lets the idle speed run too high.

When I disconnect the EGR valve and plug the solenoid valve port to the EGR, the chuggle is gone (Of course, the motor pings then, so I can't use that to fix the problem!)

Any ideas?? Thanks, Sevie

[bracketshark]

I bought a new EGR from GM once that had too large of an orfice (where the hose hooks on) it would stumble off idle every time, but this was a new piece and was easily identified as the problem and the parts department agreed. I'm not sure how the EGR could affect spark rattle in your truck, unless its staying open some. What model and motor are you dealing with anyway?

[sevie8]

It's a '92 5.7. I read that even if the EGR is disconnected, the spark control is still set up for a motor with EGR, so the timing is still way advanced. That's why the engine pings. I just took the IAC valve off and will clean that up with carb cleaner . The TPS seal is in two pieces and my book only shows one piece -- maybe that is creating an air leak. I have 147K on it, but the TB is very clean internally. Thanks