2000 S10 pickup with 4.3

[Aldon73]

My father in laws S10 runs irradict at times. When started runs at high idle for a long period of time and then after driving for a while, it won't stay running when at a standstill. What could be the problem?

[Jsdirt]

On anything built after the 1995 model year, you're going to need to supply alot more info in order for anyone to diagnose anything over the internet.

 

Could be anything from leaky injectors, to bad intake manifold gaskets, to a bad thermistor (temp. sender). Need to know what codes, if any, what your fuel trims are running at, actual engine temp vs. what the sensor says in the scan tool PID,  MAF airflow, and maybe a few more parameters I'm forgetting.

[Doug_Scott]

It would also be unusual that the check engine light is not on to indicate there is a trouble code set. 

[Aldon73]

It's not throwing any codes at all which I think is weird. I'll have to hook my diagnostic hand held to it to see what things are running at. Thanks for the info