Hello,
I recently installed a Ford Racing 70mm throttle body on my 02 Mustang GT and am having idle speed issues. With the stock TB my car idled at approximately 650 RPM, now it idles at 750. I set the idle
speed via the mechanical throttle stop per FRPP instructions and can acheive my desired idle speed of 650 with the IAC disconnected. When I plug it back in it rises to a stable 750...no surging, etc. I am reasonably confident I do not have any leaks. The IAC is new with maybe 2000 miles. The Predator tune has been in the car for both throttle bodies.
The indicated RPM shown on the tach is in agreement with the RPM in the diagnostic mode and also with an external tachometer.
What I'm extra confused about at this point is that the Predator tune idle speed is set for about 650 RPM... why is the PCM not getting the RPM closer to this number when there is apparently range left in the IAC to drop it?
Is the IAC supposed to be supplying air at all times or only when extra loads(A/C etc) are on the engine at idle?
Thanks
U7146, 02 Mustang GT, Idle speed problem
Moderator: mikel
Re: U7146, 02 Mustang GT, Idle speed problem
123xyz, there are a few reasons that the car will not idle and it is just that the calibration is set up for a stock throttle body with certain airflow at closed throttle, minimum Iac settings for idle, desired airflow etc. etc. The computer believes the IAC needs to be at a base setting to allow the correct airflow requirements and will not learn to back off further. Without custom tuning you can do it the old fashion way and just back off the screw some more.123XYZ wrote:Hello,
I recently installed a Ford Racing 70mm throttle body on my 02 Mustang GT and am having idle speed issues. With the stock TB my car idled at approximately 650 RPM, now it idles at 750. I set the idle
speed via the mechanical throttle stop per FRPP instructions and can acheive my desired idle speed of 650 with the IAC disconnected. When I plug it back in it rises to a stable 750...no surging, etc. I am reasonably confident I do not have any leaks. The IAC is new with maybe 2000 miles. The Predator tune has been in the car for both throttle bodies.
The indicated RPM shown on the tach is in agreement with the RPM in the diagnostic mode and also with an external tachometer.
What I'm extra confused about at this point is that the Predator tune idle speed is set for about 650 RPM... why is the PCM not getting the RPM closer to this number when there is apparently range left in the IAC to drop it?
Is the IAC supposed to be supplying air at all times or only when extra loads(A/C etc) are on the engine at idle?
Thanks
A few tips before you attempt the above...disconnect the battery to clear any learned values, make sure the vehicle is at operating temp, no A/C or tension on the P/S. The Ford Racing idle procedure was developed on the old Fox body strategy too I believe so you may want to bend the rules there.
Hope this helps!
Kev
SETTING IDLE
I have 02 GT and 75mm Accufab Throttle body & plenum and have no problems. The screw on the throttle should not be adjusted to set idle. Idle is controlled by the computer if idle screw is set correctly (should have been that way when you got it) and Throttle Position Sensor is set to correct .98 - .99 volts, ignition on, engine off.
After the TPS is set correctly the throttle body idle can be checked.
If set correctly the engine will barely run & stumble when the connector to the IAC is dissconnected.
After the TPS is set correctly the throttle body idle can be checked.
If set correctly the engine will barely run & stumble when the connector to the IAC is dissconnected.
Gentlemen,
Thank you for the replies. I was able to get the idle down to the desired 650 RPM by simply adjusting the stop on the throttle body while the IAC was still connected. If I continued to adjust the stop to close the throttle further the RPM stayed at 650. This tells me I was then getting into the range where the IAC and the PCM were starting to make adjustments to maintain the idle. kmac1, I think you are correct in that the existing "settings" specify a minimum IAC opening and I was fighting that. Fortunately the throttle body had enough closing range left to get me to the correct idle speed. Seems like the procedure from Ford Racing may be a little confused about later vehicles? LARRY2716, the throttle body was a used purchase from EBAY and perhaps the prior owner changed the original stop setting causing this problem in the first place.
If you guys check back in on this, how critical is the TPS voltage setting at idle? I originally had it set at .965 volts (FRPP specified .960-.980). Now after changing the stop again it is at .933 volts. I have a Haynes manual(admittedly pretty basic) which says the value should be between .500 and 1.000 volts. I will probably need to remove the TPS and drill out the mounting holes to get back into the FRPP range at this point. Just wondering if that is really required.
Thanks again.
Galen
Thank you for the replies. I was able to get the idle down to the desired 650 RPM by simply adjusting the stop on the throttle body while the IAC was still connected. If I continued to adjust the stop to close the throttle further the RPM stayed at 650. This tells me I was then getting into the range where the IAC and the PCM were starting to make adjustments to maintain the idle. kmac1, I think you are correct in that the existing "settings" specify a minimum IAC opening and I was fighting that. Fortunately the throttle body had enough closing range left to get me to the correct idle speed. Seems like the procedure from Ford Racing may be a little confused about later vehicles? LARRY2716, the throttle body was a used purchase from EBAY and perhaps the prior owner changed the original stop setting causing this problem in the first place.
If you guys check back in on this, how critical is the TPS voltage setting at idle? I originally had it set at .965 volts (FRPP specified .960-.980). Now after changing the stop again it is at .933 volts. I have a Haynes manual(admittedly pretty basic) which says the value should be between .500 and 1.000 volts. I will probably need to remove the TPS and drill out the mounting holes to get back into the FRPP range at this point. Just wondering if that is really required.
Thanks again.
Galen
What I have read stated .98-1.0v for my 2002 GT, I had to open the holes in the new TPS I bought. Yes, adjusting the throttle plate stop also changes the TPS setting. My stock was .995 volts, as I checked before pulling the plenum. The throttle plate should just pass enough air with the IAC electrically disconnected so it barely runs at idle.
Have a good one !
Have a good one !