[toxxic98]

Hello,
I am new to this forum and am looking for help for my Stang. I have 98 GT that I have recently swapped out the non PI motor for a donated motor from lightly used 2002 GT. I have been having problems with the engine idle, for some reason it wants to stay reved high after you rev it up over 2500 RPM it takes forever for the engine to settle back down to normal idle. Even while driving the car and comming to a stop we started to notice the the car was getting hard to stop. So I tried to put the car in nutral and noticed the idle was way too high, causing the car to pull and be hard to stop. I have checked everything I know to this point. I did have a C&L cold air pipe and MAF with 24# injectors that I thought might be causing the problem so I changed back to factory MAF and 16# injectors and still had same issue so changed the IAC motor and checked voltage it was ok but still no change. I am out of ideas, can someone help with this issue?

Thanks

Mike

[limited]

look for vacuum leaks

[Shaun03GT]

Im having idle problems as well. Mine isnt as bad anymore, but Hows ur TPS? (Throttle Positioner sensor) Hows ur IAC? Try cleaning ur IAC, and see if that helps. Check the voltage on ur TPS. Good luck

[Mustang03]

see if maybe the little screw on the throttle body was changed because some poeple do that

[toxxic98]

Thanks for all the feedback, I have checked the TPS and the TPS voltage which is .99 to 1 volt. The IAC has been changed and the voltage to the IAC is within specification. I have been looking at the wiring schmatics and just wondering if the CCR constant control relay might not be working properly. I have an extra one and plan to change it this week to see if there is any change. Thanks again for the replys and I will keep posting until the problem is solved.

Mike

[ndfrspd]

Hey Mike,

I also have a 98 GT and I just recently finished a motor swap from a 2002 Kenny Brown Crown Vic, which is basically the motor you have currently have. My idle used to be around 1600 rpms and sometimes rev up to 2 grand. I started checking for Vac leaks, I changed my Throttle Position sensor, its not my IAC because i can plug it and it still idles high, i check the PCV valve on the driver side valve cover which seemed to be sucking a good amount of air so that was okay, but here is one thing i didnt notice!
Whoever owned the stang before me had fu*ked around with the set screw on the throttle body where the throttle closes. I sprayed PB blaster on that screw and got a good set of vice grips on there and man, it must have rotated it 9 times counter clockwise and i got it down to 700 rpms! But just to make sure see how far that set screw is in the throttle body. Mine was almost screwed in half way and that was causing the high idle. Right now its almost all the way backed out with a low idle. check and see mike and post back with results, hope this works for you.

blake

[toxxic98]

I checked the screw on the throttle plate and it is ok, the engine will idle fine once it settles down from the high idle. I have checked the throttle plate using meter to backprobe wires and check TPS voltage. The voltage is in range on TPS and when you rev the engine you can hear the idle control valve open wide open and then slowly as the motor calms down to correct idle. I have also back probed the idle control valve while at correct idle it has around 4.5 volts and goes up to 10.6 volts when the engine is reved. It seems that the ECM is working but it is very slow to lower the voltage to the valve to slow the engine to correct idle. I am just wondering if it is possible that the intake gasket could be leaking? I really cant hear any air leak when reved due to the idle control valve air noise when engine is reved. Yesterday I changed the TPS and no noticeable changes. I am going crazy with this problem. My wife drove the car yesterday and she told me that on her way home she wanted to let the car streach its legs so she suddenly floored the excelerator, the car took off really well and then backfired twice as it screamed down the road. Now I am worried, this kind of acts like a timing issue or detonation! I am ready to throw in the towel!