rough idel help???????

help
i have a tbird sc 90 but sometimes with i turn the engine on the rpm goes up and down from 1500 to almost o (couple times the car turned off byitself) some other times the car idles ok but if i turn the a/c on or if i use something electric or if i steer the idle gets rough again, i've been reading a lot trying to find out what the problems is and i think is either the idle air control or the oxigen sensor........what do you think guys, any help will be appreciated

Typically when the engine "hunts" for the correct idle speed it is the TPS. Check that and the IAC for starters. Pull the codes and see what they are.

i took my car to the mechanic and they could not find any codes just that the rack and pinnion needs to be replaced but other than that no codes thanks flewthecoupe i appreciate your help also i wanted to tell you that i notice lately that the car runs rough when i am parking my car since i have power steering and power breaks i was thinkiong the alternator was not giving enough power what do u think? how about o2 sensor? maybe underdrive pulleys? i know this coz i been reading a lot coz i love this car and i really want to keep it thanks for your help......

How long have you had this car? Upon reading this through again, you may have underdrive pulleys on the car. If that is the case, everything is turning slower (i.e. power steering pump) and it will affect the way the car idles or operates at low rpm. What happens when you are driving and the rpms are above 1000? Does it still do this? I don't have great knowledge/experience with rack and pinion so I can't tell you that is the cause. One thing I do know is one way you'll know if you're rack is going, you'll sometimes get dead spots when turning at any speed, like you have no more power assist.

Another place you might want to register and browse/ask questions is the Super Coupe Club Of America. (http://www.sccoa.com)

Michael

i know sccoa is a great site but i took my car to the shop (2 differents) and they both think that tha idle air control valve is not working rigth so ill chenge it and let you know what happend....by the way do u think this is the problem also what do you think is the best mod for this kind of cars i am thinking of putting a shift kit or get a better exaust what do u think...thanks for all your help.....

Headers and a cat back system, remove the air silencer from the right wheel well, larger TB and MAF, etc. There is a huge list of things to do and to say "This is the best" just doesn't work for all.

check for an air leak in the supercharger tubes at the intewrcooler and on the other enda if its suckin air the car wont idle. mine idled low when it was suckin air it also missed. i had had it apart and didnt tighten the nuts on the top intercooler tube enogh. when i mashed the gas it was very erratic and didnt show a code

its me again well i just installed the new iac and helped a lot but seems like the problems still existing but the car does not runs like before......should i change the tps or not? i got another questionf if you dont mind how much hp does inclease the k&n air filter if you install it where the air box used to be you know like a home made cold air intake? also where is the computer? can i disconect it my self? should i live the car running a bit so it can adjust to the new iac? how can i check for air leaks in my supercharged? i know its a lot of questions but you seem to know a lot of this car and i feel like yuo are the kind of person that likes to help unexperienced people like me thanks alot i really apreciate you take the time to at least read this post and if i can do something for you like related to computers i could problie help you thanks once again

1. Change TPS? Get a multi meter and ohm that thing before throwing parts. I just don't remember the specs.
2. You MAY see 2-5hp increase. If you are getting the conical filter, drop that thing into the fender well and you'll have to plumb it in. If you leave it in the engine compartment it is sucking up so much hot air it won't do anything for you. Also, if you just get the flat replacement filter you can get cooler air straight out of the fender well. The air silencer needs to be removed from inside the fender well no matter which way you go.
3,4,5. Computer is behind the passenger side kick panel. No need to disconnect the computer for what you have done so far.
6. Get a can of carb cleaner and spray all of the fittings and mating surfaces. If the car starts to stall, you've found your leak.

thanks a lot for all your info now i checked for leaks and look like thier isnt leaks and the overall behavior of my car has improve since i instaled the new iac but my only concern is that when i start the car the rpm does go up to 2500 like evry car my rpm stay at 1100 rpm it seems like the engine does not rev like it should do it but everything else besides that if ok thanks again for everything by the way i do even know your real name mine is erik and live in CA so whats your name and where you live flewthecupe and actually you are not that newie are you?

It's Michael and I'm only "new" to this board. Where did you get your IAC? If it isn't OEM, take it back and get OEM. Many, many people (myself included) have had the same problem after installing an aftermarket part. Idle just wouldn't come down under 1100. Had to shift into nuetral at every light.

Hey i've been reading over all ur notes and i own a 92SC and i had the same problem with my idling after ford had if for about a month they found out it was my ignition mod giving me problems.
The modual was showing fine on dignostic exams but it was apparently not

thanks to everyone i really apreciate everything and just so you know my car looks like is running ok now it took a while but its runnig ok i dont know what happend but ever since i installed a k&n filter my car is working ok which i am so glad to tell you.
the only thing that i am concern about is that when sometimes i start my car the rpm DOES NOT go up to 2500 rpm like it should do it, instead the rpm stays at 1100 and then go back to 800 or so is that normal for this cars? another question guys some times my car leaks antifreezing but what i've notice is that sometimes the reserve tank of antifreezing is empty and some other times is full so when the tank look empty i put more water or antifreeezing in it then starts to leak. is it the watter pump? some hose? i've been trying to find the place where my car leaks from with no results oh by the way after driving my car for a couple hours it it feels like is overheating? what can i do?

thanks to all of you
and thanks god the rough idle is gone lol