'92 G30 w/5.7 cutting out at warm idle

My 1992 G30 with a 5.7L is cutting out at warm idle. Not complete stall but close. With an auto trans, it feels like you are being bumped in the rear when the trans locks after each cutout. Another possible related problem is restarting after about 30 minutes of shutdown. If it sits for brief periods, it will restart right away but will be stumbling for a few seconds until it clears up.

Engine has just had a complete new distributor, plugs (AC Delco) and wires. Runs fine on highway. No error codes showing. Can't find any vacuum leaks. Injectors seem to be spraying ok. No dripping observed. Ohm meter (analog) showed both about 10 Ohms. EGR not frozen.

What could be causing this problem that is gradually getting worse.

Thanks,
Jim

Just a guess, your EGR valve might be leaking, allowing manifold vacuum to suck exhaust gases in, even though its supposed to be closed.

Just checked the EGR valve. I don't have a vacuum tester so I sucked on the hose and blocked it for 20 seconds while holding my finger against the diaphram. The valve seems to hold.

How about the EGR solenoid? Is there any way to test that?

I've replaced the EGR solenoid but found no improvement. Also noticed that it only wants to cut out at warm idle in gear. If you slip it into neutral, it is fine and runs smooth.

I have a 1989 G20 5.7L and had that same problem of running rough, and stumbling once it warmed up, replaced the temp sensor and ran fine after. You say it's getting worse though. If it was'nt temp related I'd suggest the fuel pressure regulator. Good luck