Chevy 350 won’t idle

[89chevy4scrap]

I have a 1989 k1500 with a 350 in it that won’t idle. I’ve replaced the fuel filter, cleaned the ground for the fuel pump (which is relatively new), new spark plugs, new pcv valve. The truck almost always starts but never fails to die. It might run for two seconds or it might run for 2 minutes but it always dies. I was going to start throwing more parts at it but I figured I’d see if maybe I’m missing something simple. Any help would be greatly appreciated.

 

[WICruiser-97]

After it dies how long do you need to wait to be able to repeat the start/stop process?

If it does start does it run a high speed and only stop at idle or stop regardless of throttle position?

 

[89chevy4scrap]

As soon as the engine stops I’m able to turn the key and start it again. When it does idle it seems to be at a good speed and it can run fine for a minute or two fine. Also seems to die regardless of the throttle position, if I try and give it gas as dying it dies regardless.

 

[Drunkcanuk]

Head on over to the engine and performance section. There is a sticky that has all the factory service manuals there. Download the one for your year and follow the troubleshooting section in there.

 

[RichLo]

Has it been slowly getting worse or is it a brand new problem?

The ICM will give symptoms like that but usually it first starts killing it after a long drive on a hot day.

 

[WICruiser-97]

Monitor the fuel pressure to see if it drops before the engine stops. You should be able to get a fuel pressure tester from your local parts store for free on their tool loaner program.

You mention the fuel pump is fairly new but did you also change the fuel filter?

 

[Schurkey]

The USUAL THREE bits of advice:

1. Verify fuel pressure at prime, and under load. If the engine won't run properly, use the bleeder valve on most fuel pressure testers to "load" the fuel system. Use a drain pan to catch the bled-off fuel. Consider replacing the fuel filter depending on mileage and condition, especially if the pressure is low.

2. Verify ALL normal "tune-up" items: Distributor cap and rotor, plug wires, spark plugs. Check initial ignition timing, and electronic advance. Assure the PCV, EGR, EVAP, and heated-air intake systems (including air filter) are working properly. Verify battery voltage, and charging voltage. O2 sensors get lazy with age, if it's got more than 50K miles on it, it's questionable. Even if the O2 sensor "works" it could be reacting too slowly. Make sure the ignition coil has enough power to reliably fire a spark-tester calibrated for HEI, and that is best done with the ignition coil hot from miles of run-time, and with the coil misted with water from a squirt-bottle. A plugged catalyst (or other severe exhaust restriction) can stall an engine--check for back-pressure problems.

3. Connect a scan tool, verify EVERY sensor and computer output. Look at the fuel trim numbers. I'd be paying special attention to the coolant temp sensor, the TPS, and the IAC. You can check for "codes", but the real diagnostic power is in the data stream.