Crazy Idle problem
 

My 92 mustang will idle at 2000 then goes down to 1100 (modified motor) like it should..then while im sitting still in neutral, it will slowly climb to 2000 again, and then goes back down to 1100..then after a while (few seconds), it goes down to like 800...ihave the idle set right and the tps....what can be causing this...oh..also have new o2 sensors installed today. Thanks guys

Start by retrieving your codes. When you say you have the tps right, does that mean it's at .9 volts or so, or are you trying to set it for .99 volts?

You should reset your computer and then let it idle for about 10 minutes to let it relearn your new components.

Check vaccuum connections.
i actually created a vacuum leak to make my car idle right, but the e-cam i have is notorious for that stuff.

What about the ilde control valve on the side of the TB? Would they get dirty or anything?

yes, clean that with some tb/carb cleaner, worth a try being those things are like 50$

Ok, thanks guys!

Did you not get any codes? I'd check that and the vacuum lines before I start pulling stuff apart.

havent checked codes yet, but will check hoses again

idle control problem fix (most likely)
 

if your idle is jumping around 9 times out of 10 its your idle control, its actualy pretty comon on 5.0 87-93, when my car started doing it i was going nuts yhen a freind pointed it out to me that thats what it probably was, first make sure your sensers are all working proper maybee get a code readout, then clesn the idle control unit, yhey get realy dirty. In my case i cleaned it and that was it problem solved, but 6 months later did it again so i replaced it and its never done yet for 2 years. just a little tidbit i thought id share with you, good luck.

I cleaned mine real good and no help....so im getting a new one today..thanks guys! Ill let ya know if it works better

Drill a small hole in your TB flap this helped mine idle right when I had my e-cam- Also clean your TPS and then unhook your neg. terminal for 30 minutes. Rehook it up idle the car for 10 minutes then drive in stop and go traffic for 30 minutes. This should help you out some. What kind of cam r u running? Good luck---Bri

What codes did you get? If you haven't read them yet, why would you just start replacing parts that may not even have a problem? There are a bunch of things that can cause a rough idle.