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1994-1995 5.0 Mustang SN95 Tech Forum

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Unread 04-26-2011   #1 (permalink)
302Feen is offline SHELBY GT 350 Member


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Default Strange Idle Problem 1994 Mustang GT

I just installed a 70mm TB onto my Stang. Before installing it I cleaned the heck out of the IAC, but ever since it's all been installed I have a strange idle issue...

When I first start it it wants to idle a tiny bit high (maybe around 1K RPM or a tiny bit more) but when I start moving the idle will only go down to around 2300ish RPM... until I come to a complete stop. Once I come to a complete stop the idle will come back down to around 1K RPM. But if it's moving at all the it only idles at 2300ish.

Does this sound like an IAC, TPS, or vacuum leak?
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Unread 04-26-2011   #2 (permalink)
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try unplugging the iac and see what it does.. the idle should drop down after revving rather quickly... if theres no change i'd definitely check to see if its sucking air somewhere after your throttle body install.. get some brake cleaner or carb cleaner and spray around the gaskets and see if theres any change in idle..it will either die or rev up when it inhales the spray

also, when you installed the throttlebody did you make sure the voltage was set on the tps.. the symptoms dont really sound like a tps problem, but since it was recently touched i figured i'd ask
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Last edited by kyle89gt; 04-26-2011 at 03:32 PM. Reason: forgot something
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Unread 04-29-2011   #3 (permalink)
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Quote:
Originally Posted by kyle89gt View Post
try unplugging the iac and see what it does.. the idle should drop down after revving rather quickly... if theres no change i'd definitely check to see if its sucking air somewhere after your throttle body install.. get some brake cleaner or carb cleaner and spray around the gaskets and see if theres any change in idle..it will either die or rev up when it inhales the spray

also, when you installed the throttlebody did you make sure the voltage was set on the tps.. the symptoms dont really sound like a tps problem, but since it was recently touched i figured i'd ask
Yeah, acutally this WAS the problem. When I first saw the new TB, I noticed the TPS on the new TB was strange. It had two allen head bolts that hold an adjustable mount on. I didn't think anything of this until I read my TPS voltage and I was at a little over 2 volts at idle (key on engine off of course). So I actually had to read the instructions... I know I know I'm embarrassed... But finally got the TPS adjusted correctly, and sure enough it runs ten times better and I CAN tell a difference in acceleration with the new TB. When I put my GT40 intake on, I kept the stock TB and didn't notice much of a difference. But now that I've put the new TB on, I think that put the intake to it's full potential.



So basically, with the high voltage on the TPS, the car was assuming that the idle needed to be higher than normal. So just as a helpful tip to others that have a same issue, check TPS voltage first. Correct the voltage, adjust and correct your timing, reset the battery and take it for a spin.

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-1994 Mustang GT "The Red Baron": 3.73 gears,K&N filter,GT40 tubular intake,BBK Full Length Headers,modified midpipe & Flowmaster muffs, timing at 12*. Best time- 14.74 @ 93.16
-Check profile for pics of our car collection!
- AmericanMuscle ROCKS!!
- "True Hot-Rods don't have valve covers!"
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