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Shawn, Auto Service Technician
Category: Ford
Satisfied Customers: 3756
Experience:  16 years experience Ford,Nissan and Honda dealership in all areas
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1997 Mustang Cobra: under load..second compressor

Resolved Question:

My 1997 Mustang Cobra really hesitates and bogs down under load mostly in second gear under hard acceleration,hesitates in all gears under acceleration,also when AC is on when i stop at a light the car idles at 2000rpm and then drops down to 12oo and then to 600 and then stalls ,this all happens in about 20 seconds.When ac is off it idles normal.Just had a brand new ac compressor installed,AC is working.
Submitted: 7 years ago.
Category: Ford
Expert:  Shawn replied 7 years ago.



Thanks for using Just Answer, the first place I would start based on the description you have given sounds like you have either a stuck or defective IAC (Idle Air Control) valve. In that case the IAC must be replaced.





Customer: replied 7 years ago.
I took it off and inspected it ,cleaned it and hooked up the wires and had someone turn on the key i could feel something click inside but the visible part of the mechanism did not move. I s it also possible the feul pump is fail to deliver enough feul under heavy load and that is why it feels like it running out of gas in second gear?
Expert:  Shawn replied 7 years ago.



If there is no movement, then the IAC is defective. Also if the fuel pressure is inadequate and below specs this can also cause a misfire, and poor performance.

Customer: replied 7 years ago.
Changed the IAC and at first it seemed toidle and run a bit better ,took it for a drive and it still hesitates and surges and stopped at a red light and the idle was at 2000 and slowly dropped down and ended up stalling like it did before.I believe the idle only does this if the ac is on.
Expert:  Shawn replied 7 years ago.




The next step will be to clean the Mass Airflow (MAF) sensor. To clean the MAF sensor, carefully remove the plastic sensor from the aluminum housing, and spray the sensing elements, at the tip of the sensor, with electrical contact cleaner, or a good brake cleaner. Do not use any cleaner that will leave a residue like carb cleaner. Check the sensor passage in the housing for any debris, and if the housing inlet has a screen, make sure it is also clear of debris. Let the sensor air dry, then carefully reinstall it in the housing.

Reset the Powertrain Control Module (PCM) adaptive strategy by disconnecting the battery for more than 5 minutes. This will reset the PCM's BARO calculation to a default value, usually about 150 Hz.

Drive the vehicle, and do at least 3 or 4 hard-throttle accelerations, holding at least one for several seconds, as traffic laws will allow, of course.

After driving, recheck the BARO reading. If the reading is within range for the shop's elevation, the codes should not return. If the BARO reading has returned to a low reading, and the MAF sensor was just cleaned, it should be replaced, then the reset and drive procedure repeated.


There also is a TSB (Technical Service Bulletin) from Ford in regards XXXXX XXXXX situation, hope this helps you out.


Click Here for TSB

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