Hey guys, have a small problem and wanted some of your input, I have a 93 F150 5.0 5spd, and it keeps over revving, it will start off normal then rev to 2 grand and stay there, its erratic.. It doesnt wanna die, doesn't even drop below the normal idle rev, Any idea what this could be? Idle Air Control Valve? I replaced the TPS sensor I wanna say 2 years ago but am not 100%

 

Sounds like you have an air leak somewhere. Also double check the throttle plate is closing and the throttle cable isn't binding. Fast idle I would suspect around the intake manifold gasket and everything that bolts to it like the EGR and the throttle body.

I would also check for codes, the ECT (engine coolant temp) sensor is also known to cause some wacky idle problems if it isn't working right.

 

Here is a video of what its doing:

http://videobam.com/OTPXR

 

Interesting how it creeps up then just dies down. I would still check for engine codes. You can also find air leaks by spraying carb cleaner around the intake, throttle body and EGR gaskets with the engine running. If the idle suddenly changes you know you have a leak.

 

Ok so did some more playing around today and did what you said, i unplugged the air idle control and the truck didnt die, it idled normally, went and got a new idle air controller, switched it out and started it up, started up a little high around 2k then comes down. Is this normal? Whats the normal start up rpm? It idles better but it still jumps a little over 1k now idling, then goes back down...the air induction (black plastic vent at the rigt front of the engine) tubing seems loose, it sounds like it gasps more air and then the rpms raise... Thoughts?