ok my car is a 94 z28, im having issues were 20-25mins after i start the car from a cold start its stalling. once it stalls out usually you have to wait about 30secs to restart it and even then it will only run for maybe a minute, the longer you let it sit the longer it will run but never seems to run more then 25mins . and on colder days like temps in the 40's ( ran it once when temps were about 45 out and ran for over a hour and never stalled) it seems to not have the issue, but on 60deg days it acts up?? replaced the following things and still has the same exact issues as it did before. new opti, new ICM, new coil, disconnected the MAF still same, checked my ICM and coil wires for any cracks and all appears good, even disconnected my 6al and still the same?? running out of ideas here if i try to restart the car right after it stalls and keep it revved to about 1500-2k rpms it seems like i can keep it running but as soon as i let off it dies?? any help would be appreciated

 

Have you scanned it for codes? Have you checked the fuel pressure? Hopefully you did that, before throwing all those new parts at it.

 

no havent scanned it for codes because the SES light wasnt on but i do want to buy a tool to scan it, whats a good scanner for a 94? (meaning could i find a descent one at a local auto parts store that scans obd-1?) and yes fuel psi is good. ive read alot of guys having similiar issues with the opti causing this problem, when i swapped my opti out i just got a reman one from autozone, i kept the cap and rotor cause it was only a month old and looked like it did the day i put it on, possible the cap is the issue or usually heat related problems with the opti is the optical sensor?

 

Disconnect an O2 to force it to stay in open loop and see how it does.

 

well today its a lil cooler outside then yesterday ( about 10deg) and now it wont stall out,lol! im also wandering if it is fuel related cause yesterday i had 1/4 tank of gas and i went and filled it up today so either the cooler temps outside or now since it has a full tank of gas it isnt stalling out??

 

But you said "yes the fuel psi is good". How would low fuel be a problem, if the fuel pressure is good? What was the exact fuel pressure, at idle with and without the vacuum compensation line connected, and at WOT/max engine load?

Best bet for scanning OBD-I is software like TTS DataMaster or FreeScan. Gives you a data log of all the engine sensors, PCM parameters, and trouble codes, allowing you to look for what's going wrong when it isn't running right.

 

psi is 38psi vac line on ( running off a pcmforless tune right now so thats his recommended setting), 45-46psi off. this is a racetronix 255 pump btw. but also with a full tank of gas. possible for a fuel pump to heat up and die when beetween 1/4-1/2tank if its going bad but then run fine with a full tank?

 

Heat buildup in the tank is a possibility. That may be promoting vaporization of the fuel. What are the mod's on the car? What necessitates the 255 LPH pump? Do you have an exhaust system that might be too close to the fuel lines? Are the heat shields still on the tank area? Is your EVAP system, and its pressure control valve working? When you pop the fuel tank cap, do you sense pressure or vacuum?

But the most likely spot for vaporization is on the suction side of the pump. Do you still have the bucket? Vaporization on the suction side would show up as a loss of fuel pressure, which you say you don't see.