Hi all. New to the board. I just picked up an '89 Iroc-Z with the 350/5.7 TPI. The car is in decent shape with minor problems. The biggest problem I'm having is with long periods of idling. If I let the car idle for 10-15minutes, it will stall as soon as I put it into gear and will not restart. It turns over, but won't fire. If I spray some starting fluid into the intake, it will fire up right away and then run fine. And it only stalls after idling for an extended period of time. It never stalls any other time. Any ideas? Help!

 

More info.... the car will restart with no problems after sitting for 15-20 minutes. Fuel pressure regulator?

 

Ok, the problem got worse tonight. The car runs poorly and starts to stall once it gets warmed up. As soon as it gets to operating temperature, it starts to stall at idle. The idle seems to be hunting and drops as low as 500, at which point it usually stalls. After stalling, it won't restart until it cools down a little(about 20 minutes). The car isn't throwing any codes. Any ideas? This is my new winter daily driver and I don't know anything about it. Help!

 

I would do a complete tune-up, plugs, wires, set the minimum air, and set the static timing. Run fuel injector cleaner thru it.

Does it run hot, and what is the fuel pressure?

What does the alternator do, up the voltage or weak?

There is probably just one reason why it does this, you need to be a detective and check things out.

 

How well does it idle once it while it warms up? Idle speed, smootheness, etc.

I agree with doc, try checking the fuel pressure when it's in near-stalling condition.

Obviosuly air, spark, fuel, and compression are the 4 things required to start an engine. You have air obviously. It's cranking, so you have compression. It fires up with fluid, so there is spark. That leaves fuel.

But again, working with a good state of tune makes things easy(er).

 

I was thinking fuel pressure from the start. What should the pressure be at idle, cruise, key-on?

 

Cruise? I don't know if anyone can answer that, since load (and vacuum) at cruise will vary widely.

At idle, pressure should be 37 PSIG, ± 3, and with KOEO, the pressure should be 43 PSIG ± 3. Make sure the pressure maintains for at least 15 minutes after shutdown.

 

Okay, I'm gonna be scanning it and checking the fuel pressure on Monday, but I was hoping to get some other ideas of things to check in case I don't find anything that points to a possible cause for this. The car is almost undriveable now (it ran fine less than 48 hours ago). The only thing that really changed is the weather. It was in the 40s and 50s the other day when I bought it, and now it's gotten below freezing (low 30s). It runs poorly and wants to stall whenever it idles, and once it gets warm, it gets even worse. Once it reaches operating temperature, it stalls whenever the RPMs get down to 600-700 range. It will restart, but then stall as soon as I put it into gear. Any other ideas? Thanks guys!

 

After you do the scan, if it shows up that you have low fuel pressure, start simple. Replace the fuel filter, make sure the injectors arent stuck open or something, then see where it goes from there.

 

Ok, just checked the fuel pressure. The highest it goes is 40-42 psi. Most of the time it's down around 35 psi. This is low enough to cause the problems I'm having, right? From what I've read, it should be close to 50 psi. Has anyone ever had a failing fuel pump with these symptoms?