Hello all, first posting. First of all I have read through several pages of useful info and searched for a similar problem before posting. I will admit I am new to the blue oval(dads retired from GM) so I dont have a lot of experience working on them. However, I have a 94 F-150 with the 5.8 and it is idling too high, drives fine except for when I do drive it it will be at 40mph.... checked for vacuum leaks, hoses as well as intake gaskets. no fuel in the line attached to the pressure regulator. cleaned and lubed the IAC according to another thread I had found on here to no avail. The one thing it does do is when I unplug the electrical connector from the IAC it idles down and dies. Any suggestions? Maybe check the TPS? Any help would be greatly appreciated!

 

I had a similar problem on my 96 5.8 (No OBDII) and it was the TPS, though it wasn't shifting correctly either, and would rarely go into third. As soon as I unplugged the TPS she settled right down, but didn't stall. Based on that, I replaced the sensor and everything has been fine since. Well, with the idle anyway.

Steve

 

Ford Fuel Injection Throttle Position Sensor (TPS) Here is a link for info on the TPS. Stephen could well be right on that.
If you look on the right of that page you can click on Self Test for info on pulling trouble codes without a code reader.

 

Thank you all very much. I will definitely be getting the volt meter out and and checking the TPS!!

 

Anybody fiddled w/ the throttle adjust screw?

 

I don't think you want to go there. I do not usually take someone's word on anything unless it can be backed up with a manual. In this case I have read several manuals stating you do not want to "fiddle" with that screw. Steve83 posted a procedure for how to reset it quite some time ago.

 

It was a question, not a suggestion. That's why I said "Fiddled" instead of "adjusted". But I suppose someone might take it as a dare! Better safe than sorry! (and they would be)

 

Gotcha....my mistake for reading that wrong. But that is a good point and more than once an OP has found that to be the case. In this example the OP has disconnected the IAC and the idle drops, so I would say something is telling the IAC to open the throttle too far such as the TPS?

 

One of the two. or a horrendous unmetered air source. I was hoping to rule out "fiddling" now, instead of him copping to it, 2 pages of posts after he replaced the TPS to no avail! People think it's the same thing as back in the Carbed days. Nope. Rereading it, it did almost sound like a dare. Now I'm picturing him w/ a little devil on one shoulder saying, "Go ahead, give it a little turn. The first one's free! I too was thinking TPS, but if the set screw was adjusted then his TPS test reading would appear out of wack regardless of weather the sensor was actually good. Yes?

 

Yep, it sure would