My dad has a 92 3.9 that doesnt want to idle or run at times. I started acting like it was the fuel filter, put 2 on then dropped and cleaned out the tank. No help. Changed the TPS and it seemed to help for a couple of weeks but then it starts acting up again. Dad is a long haul driver so the truck sits more than it runs, I drive it a few miles once a week just to keep everything going. Like I said this problem comes and goes it happens when the engine is hot or cold. Some days you can get in it andd go others it takes 5-10 minutes to get it to stay running. You can rev it while its doing its thing but let off the gas pedel and it just dies. PLEASE HELP I am tired of messing with it. It only has roughly 80,000 minles on it.

 

Probably a bad IAC Idle Air Control valve, they are known to be bad even when new. Next possibility is a vacuum leak.

 

Thanks Crazy I will try that and see what happens

 

Well TPS and IAC have been replaced and still same thing. I will try to die while at idle real bad if in gear but as soon as it trys to die if you hit the gas you could melt the tires off of it if you wanted to.Runs great other than idle and just off idle. Im out of ideas