My 94 Mercury Sable had problems idling. It started by swinging wildly from 500 rpms to 1500, and then after a couple of days it would just die if I didn’t keep the gas pedal depressed. I changed the TPS sensor, as well as cleaning out the IPAC with carb cleaner and adjusted the idling screw. This worked for about a day, but today I noticed that even though I adjusted the screw yesterday - at 1000rpms idling, it went down again to 800rpms today.
It sounds like you have a lazy IAC motor. You may have cleaned the IAC motor, but on Ford vehicles when an idling issue arises, and if cleaning the IAC motor doesn’t solve it, replace the IAC motor.
First, If you do not have a scan system don’t change the idle air screw period.
Second, you are chaseing the problem. You don’t know what it is but you are putting in parts. Do not do this. Get the car scanned. It is odb11 and there should be a bunch of info on a good scan. Yes it could be an IAC motor but it could be bad spark and bad o2 sensors and bad injectors and… The computer has a lot of leeway to adjust the system before the closed loop starts. You need a scan or a good mechanic and stop putting in parts.
It’s the IAC or Idle Air Bypass Valve as Ford called it. It’s a solenoid valve, not a motor. Sticking closed is not an uncommon problem. The part being sold now is redesigned to be less likely to fail.
(When they stick closed, it takes more than just some spray cleaner to fix it. You are better off to replace it (about $80). Also, a stuck IAC will not set any OBD code.)
The screw you adjusted is not the “idling screw.” It is the throttle hard stop, and it will have to be set back correctly for the new IAC to work correctly.
This image shows the tool you need for this problem: http://www.autozone.com/autozone/catalog/parts/partsProduct.jsp?skuDescription=Chilton+/+Manual+-+Vehicle+Maintenance&categoryDisplayName=&fromString=&itemIdentifier=761497_0_0_&productId=761497&sortType=&parentId=12-0&filterByKeyWord=idle+air+control+valve&isSearchByPartNumber=&navValue=11200108&categoryNValue=11299999&fromWhere=&itemId=108-0&displayName=Manual+-+Vehicle+Maintenance&store=1140&searchText=&brandName=Chilton