[StAnG89]

I have a 1989 5.0 Mustang. Lately the idle has been getting stuck at around 1500-1600 rpms. I will be driving the car and I will feel it get stuck at high engine speeds (usually this happens once the car heats up a bit). I press in my clutch and the rpms remain where they are, they will not return to normal idle speed. I cleaned out the idle air control with carb cleaner, checked my vacuum to make sure it was normal, cleaned out the throttle body, lubed the throttle body linkage, put on a new throttle position sensor. Then I tried switched to a friend's idle air control and switched to a friend's MAP sensor. I also noticed that when I rev the car the rpms stick for a second or two when they fall to about 1100-1200 rpms. I turned the timing back to about 8-10 degrees, maybe I should turn that back to about 12-14, but I'm not sure what would be best for the car. THe original owner had it at about 14. I have got no idea what could be causing this to happen? If anyone has any ideas please let me know because I am going crazy and I want it to run normal again so I can keep racing!
1989 5.0
Edlebrock Performer Intake Manifold
Hooker Competition Headers
3.55 rear end
Underdrive pulleys
Custom Exhaust, no cat-backs w/ flowmaster mufflers

[Blade10]

14 timing is pretty common for performance, but usually forces the use of premium fuel. 10 is stock.

The idle staying up is usually either the throttle plates not closing or the IAC motor is stuck open. Id try setting the throttle plates and the TPS as per the TPS sticky.

Blade

[StAnG89]

Thanks, but how do you set the throttle plates? I have no clue.

[lordbremn]

Check your Throttle position sensor, it may be out

[89GTVert]

I would yank your intake tube and actuate the throttle plate a few times by hand to see if its sticking. you can turn it (and adjust it if needed) from the underside of the throttle body. just look to see if its getting stuck before you do anything crazy. It sounds like a mechanical problem to me, not a sensor.

One other thing, if you do mess with the throttle plate adjustment you will have to re-adjust the TP sensor to match it.
here is a link to one of the threads that talks about it, just in case you need it.
http://www.allfordmustangs.com/forum...&highlight=TPS

[Skinney]

I bought a used 70MM Edelbrock tb of a guy whos gf put his car into a pole because of a stuck throttle. When I checked the throttle body, I sort of felt like Grissom from CSI...upon further investigation, I found that he had replaced his TPS with an aftermarket unit, even with the tb off the car, when I opened the tb up all the way it stuck open. Swapped on my Ford unit, no problems after. This might not be your problem, but may be worth a look.

[StAnG89]

Thanks, I'll check those ideas out and see if it helps. Also I know my idle air control opens and closes, but is it possible it is getting stuck? I was thinking probably the throttle body or IAC would be the cause, just like 89GTVert said it is probably mechanical, any more ideas I could check into would be much appreciated and thanks to all who have gave ideas so far.

[84 predator mus]

even though you lubed the throttle cable, the cable itself can still be bad. my 89 gt did that and one day it stuck full throttle when i mashed the gas. not so fun experience especially in busy traffic lol. i'd check your cable and see if its cracked. also i took my stock throttle body off and pulled the butterfly out of it and it was clogged with crap. just some ideas.

[StAnG89]

As of late the idle has not been getting stuck, but sometimes it jumps from normal up to about 1200-1500 and then it goes back down, so i am starting to think that it might really be the throttle cable, if anyone has some more definite ideas i would really appreciate it, thanks in advance.