Have an 89 ford 150 5.0 302 automatic. At start up whether it is warm or cold it jumps to 2000+ rpm. Seems to be a little lower warm though. It falls down to 1100 to 1300 after a minute or two. The highest idles are in park and nuetral. In drive or reverse it sticks around 1100 to 1300 unless I give it gas and it stays high for a few seconds and falls back to the 1100 to 1300 range. No one seems to be able to pull any codes on it. I have change plenum gasket, iac, and tps. No vacuum leaks from what I have check with my mechanic stethoscope. It idles and drives fine with the iac sensor disconnected. Butterfly aren't sticking and are closing fine. It runs rich and when the iac sensor is disconnected the transmission slips if I goose it. With sensor connected transmission works great. My next move is map sensor. Anyideas?

 

How do you know that it is running rich? Sounds like a vacuum leak. Use a propane torch without the flame to find out if it has a vacuum leak.

 

I can smell it running rich. I and many other friends have ran the vacuum line up and down. I feel that it's a leak but I'm less mechanically inclined than my friends. Who all say it's a sensor problem

 

also, how would I go about using the torch test. What would I look or listen for? Run it over the lines or through the untake?

 

Run it over the lines and listen to the engine. It will speed up if it sucks propane into a vacuum line. Just be careful and don't get too carried away and put it on the hot exhaust manifold. Could start a fire.

 

Haven't got a chance to check yet. Got a propane torch setup. I was able to find time to run blink code and got 33 (egr valve open not detected) and 41(lean mixture).

 

Lean mixture is usually a vacuum leak. This could be tied in with the EGR system.

 

lean mixture can be low fuel pressure./fuel pump/fuel filter/fuelprerssure regulator