Hello everybody,


I am new to the forum but not new the automotive world, I have been having this problem with my brothers truck for a while now and I cannot figure it out. When you start the truck, wether the engine is warm or cold, the idle loops up and down and eventualy stalls. When you put it in gear, it does the same thing. No vacuum leaks, cause I sprayed the plenum and the lower intake with brake/carb clean and the idle did not change. So it has to be a sensor. I have my suspisions that it may be the IAC...or the TPS but I dont know. Just looking to see if anyone else has had this problem before or any tips on how to fix the truck, cause I am stuck.

Thank you to anyone who reply's

P.S. She is a 1992 F150 with a 302.

 

Could be a bad egr or plugged PVC. Or a stopped up air filter low fuel pressure or bad head gasket and or worn cam lobes.

 

as soon as you guy's figure this out let me know

 

I dont think it is any of thoes things...Because i just rebuilt the motor, and she has a new cam, new PCV and filters, and EGR is functioning properly. Was told that It could be a IAC sensor as for that is the ONLY sensor that I have not replaiced. That and the TPS...Still looking for tips.

 

New timeing set?

 

Yep. I installed a new timing gear set from Comp Cams. But it does have a "mild" cam in it. Also from comp cams. with flat lifters as opposed to rollor ones and longer push-rods to make up the difference in lifter size. Valve train is all new...

 

Now that could have somthing to do with it. Look at Lazer cams web page and call bill here in memphis. Ask him about that set up to see if it could cause your problem. Toll free num on web page.

 

My 92 351 would lobe up and down so much that I would have to hold the gas and brake at stop lights. I tried everything including fuel filter, regulator, 02 sensor, and finally a Throttle Position Sensor. This fixed it. A little hard lesson learned, when you replace it, replace the little rubber hose that feeds coolant into the throttle body. I found out the hard way that it squirts coolant into the alternator and ends its life fairly quickly. You can check the TPS with an ohm meter but for about forty dollars (with connections) you can replace it.