SURGING AT IDLE WITH A/C OFF AFTER WARM- 1995 350 TBI

[350TBI]

1995 GMC C1500 350 tbi with a rebuilt 4l60e 275k- has been idling really rough in park surging and ultimately stalling after a few minutes usually with the ac off. Truck runs good when given throttle but the surging and stalling is driving me crazy I’ve tried everything. Replaced EGR valve, Map Sensor, IAC Valve, PCV Valve, TPS, vacuum lines and hoses, Distributor Cap and Rotor, Plugs and Wires, Intake Manifold Gasket, Throttle Body Gasket, Valve Cover Gaskets, Fuel Pump, Fuel Filter, all in the last month or so just tossing money at the truck. No mechanic in my area can help me out any assistance or directions would be appreciated. I love this truck and will rebuild it 20x over before getting rid of it. I appreciate any advice !

 

[1997]

i don't see O2 sensor in your list of parts, how old is it?
my 95 had what sounds like a similar issue and the O2 sensor was the culprit.

any codes, OBD1 can set codes without turning on check engine light.

there were a couple of threads on similar issues, do a search might help you out.

if i get time i'll see if i can find them.

 

[Schurkey]

Verify fuel pressure.

Connect a scan tool, look for codes, but more important--look at the data stream when the idle is poor. Verify ALL sensors.

Consider a faulty magnet on the distributor pickup-coil area. Common on TBIs. Can cause all sorts of problems including stalling and misfire.

Magnet cracked through rivet-hole, just under "Copyright" symbol.

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[1997]

Might give you some ideas,

Surging idle on cold start

Hello everyone, my first post! '94 5.7 TBI with 145,000. Truck is original and last year developed a miss/bad idle in gear. I replaced the IAC, TPS and EGR, plugs, wires, cap, rotor, still had the problem. Checked the fuel pressure, good, 13 psi. No codes. Next, I noticed that the...

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