(yes another one of these post lol, but it's 105* this week)

88' 350 TPI (mostly stock)
new parts.

• MAF
• Fuel Pump
• FP Regulator
• Plugs\Wires\Cap
• Ignition Coil
• Wide Band O2
• Various wiring replaced to eliminate some voltage drop

Been getting the car working after sitting in storage for 18 yrs. Thought I had everything working, as I could drive it around no issues for 20-30 mins or longer at a time for several weeks. Took it to the store, got gas (good gas) and was driving it home on the service road, was giving it some gas (3/4 throttle) and started to drop off and was backfiring loud enough I thought I blew an engine.

Had to baby it home, couldn't give it any gas or it would die. When you start it when cold, runs perfect, can give it plenty of gas and drive it hard. But as soon as it warms up after 10 or so mins, it'll just stall, everytime. Cool off for 30 mins, and it'll run for about 2-3 mins and stall again (and repeat.)

Things I've checked..

• Fuel pressure is perfect, I don't think it's bad gas as it runs perfect cold.
• With timing light hooked up, it'll fire spark even when dying until it completely stops
• O2 readings are perfect, sitting around 14.5 until it dies
• No SES light
• Timing is correct with (whatever the connector is) unplugged
• Checked with TunerPro, everything looks good.
  • no knock
  • Injector Pulse width is constant until engine dies (looks like the ECM is trying to keep it running.)
  • TPS voltage is fine
  • IAC position doesn't change (though again when starts to die the ECM begins to open it.)
  • MAF voltage looks consistent

The only thing I can't actually guarantee (at least not until it gets darker and I can hook up a noid light) is that the injectors are actually firing, but as the ECM looks to be trying to increase PW, I don't think the ECM is cutting fuel.

What am I missing that I should be looking at?

 

Fuel tank might not be venting properly. If you'll search you'll see similar problems.

 

good point. forgot to mention I pulled the gas cap off to make sure it wasn't a pressure issue.

I went ahead and changed the ignition control module, was stamped GM, so pretty dang old. It's running now. will let it idle for another 15 mins before I take it for a test drive to see if that was the issue.

 

Was the ICM the problem? I have a similar issue and thought it might be the ICM, but someone suggested fuel pump (don't think so) and another suggested ECM (I hope not).

 

Looks like I am getting the same issue, runs fine when cold but as soon as it has warmed up or I switch it off and then go to restart it it won’t idle.
I have replaced
Temp sensor
Throttle Position Sensor
IACV
Maf Sensor
Fuel Pump
Fuel filter
Plugs
Leads
before any of this was replaced it wouldn’t idle at all and just wanted to cut out plus it ran very rich, now it runs when cold but not once hot but still runs a bit rich, not as bad as before.
I will be checking the fuel pressure, anything else that needs to be replaced?
TIA.

 

Coil and ICM would be my first suspicion. Typically they run fine until they get too hot and the engine starts breaking up and shuts off. Then once it cools down it starts like nothing ever happened.

Earlier this year I had practically the same issue. After a long drive on a hot day it slowly started breaking up past 4500rpm, then 3500rpm a few minutes later, 2500rpm, then anything above idle would misfire. It gave me just enough time to pull it onto a side street before it backfired and shut off. Got it towed home and an hour later it started right up like nothing happened. Replaced the coil and ICM at the same time and it hasn't happened since.

 

Thank you Tylersteez for the reply and advice, will be checking these and replacing as necessary or may just replace, would you know which icm I would need 4 pin or 7 pin so I can get them ordered and just replace them or is it a case of taking the cap off and checking?

 

I had this same issue this summer, check out your idle valve. Also a bad fuel pump can do this. If the fuel pump can't keep enough pressure it might stall. Also try starting it with your foot on the gas and give it a couple of revs to like 4000-4500rpms, it might not stall then. Then it probably would be the fuel pump.

 

iacv is new and fuel pump is new, got it sorted now as it was the timing that was out, now at 6 degrees btdc as it was at 4 degrees btdc