2005 Ford Mustang IDLE HUNT

Tiny
PHILLIPS49
  • MEMBER
  • 2005 FORD MUSTANG
  • V8
  • 2WD
  • AUTOMATIC
  • 55,000 MILES
The car is a 2005 Mustang GT, 4.6L 3V automatic. The car is factory stock no mods.
I had to change the battery, The old battery was developing a shorted cell. After changing the battery over 3 weeks ago, I now have a problem with surging idle. It hunts up and down between 400 and 750 RPMS. It is amplified with the AC on. It sets a DTC p0506 "Idle RPM lower than expected" I can't find any vacuum leaks or air leaks. I followed a learn procedure, but mine must be really dumb. It hasn't learned anything yet. The air filter is stock and new. I replaced the TPS. No difference. There is no idle air control valve.
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Friday, October 3rd, 2008 AT 4:21 PM

5 Replies

Tiny
MERLIN2021
  • EXPERT
The IAC is now called the electronic throttle control motor, and you do have one...on the throttle body!


http://www.2carpros.com/forum/automotive_pictures/62217_Mustang_1.jpg

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Friday, October 3rd, 2008 AT 4:36 PM
Tiny
BARKLEE
  • MEMBER
I had the same problem I also have auto. FIRST remove the positive red battery terminal to start work. I removed entire CAI also TB, cleaned everything with carb/tb cleaner that you can get at ford also known as tune up cleaner. 2 sensors replaced throttle position sensor on the left of TB and the MAF. If you can't afford use electronic cleaner or non residue cleaner or MAF sensor cleaner and clean all sensors. Also spray the connectors with electronic cleaner. The TB had black gunk behind the butterflies. Also if the air cleaner is old replace or clean. I had the steeda cone filter. I cleaned it with k&n filter cleaner. I let it sit overnight everything to dry. The next day I did not over spray the filter with the special oil provide by k&n. I but the whole system back making sure all bolts tight and no air leaks out. FINALLY, return battery terminal back. With my diablosport tuner returned the original tune back to car waited a few minutes then returned the steeda/performane tune back to my mustang. Cycled the key then started. WOW
the car runs like brand new no idle surges no low idle p0506 no intermitant mass air volume blah blah
p0104. No check engine light the car is faster. Do this if you don't have any other problems with your car and the only codes are the above mentioned. After a few years the system gets dirty needs cleaning don't let dealer tell you that you need custom tune don't trust them to clean the system do it yourself, you only know how good is.
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Sunday, October 26th, 2008 AT 7:51 AM
Tiny
MERLIN2021
  • EXPERT
May be a cleaning, but if you remove battery terminals to protect against accidental grounding, it's the (-) negative you remove.
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Sunday, October 26th, 2008 AT 8:24 AM
Tiny
PHILLIPS49
  • MEMBER
Been meaning to get back to you guys with a responce. At first, I didn't think the information would be useful. After cleaning the MAF and replacing the the TPS I still had idle problems. I also had a throttle lag. Push the pedal gently. Nothing. Then all of a sudden the RPMS would jump up. It was also nearly impossible to hold a set RPM in neutral.
After reading the mechanics reponse, I bit the bullet and purchased a replacement throttle body which comes complete with the TPS and Throttle motor from Ford Discount Parts. It is now running as good as new. I think the throttle motor may have been bad. Thank you all! It is once again a pleasure to drive it.

Don
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Tuesday, October 28th, 2008 AT 10:41 PM
Tiny
MERLIN2021
  • EXPERT
Next time read the mechanix answer, not the guest!
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Thursday, October 30th, 2008 AT 3:33 PM

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