hatecars
Member
- Joined
- August 12, 2010
- Messages
- 28
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- Year, Model & Trim Level
- 2003 Mountaineer
When you unplug the MAF, the PCM looks up the "Load w/ Failed MAF" table, and fuels from it instead. If your truck is bone stock, this is a very accurate table, and the vehicle will run and idle fine. You should also know that MAF failures are not common, and the sensors aren't cheap, and the aftermarket sensors are junk compared to the Ford sensor. Don't buy a MAF, you'll most likely be wasting your money.
You're painting a picture here. You've got both banks lean. The idle surging comes from the lean condition causing the motor to nearly stall. The PCM detects this low rpm, and compensates hard for it, raising the idle via the IAC motor. It overshoots the desired idle rpm, and suddenly the IAC closes and RPM plummets. Then, the whole process repeats. This is the up and down idle speed you're experiencing.
As long as your IAC is clean, and it probably is, this is not your problem. IAC is idle air control motor. It's a solenoid that bolts onto the side of your throttle body.
In searching for a picture of an IAC for you, I ran across this thread that you need to read!
http://www.explorerforum.com/forums/showthread.php?t=217062
First, thanks for you continued help..
I found my IAC, will clean it today..
I read the post your sourced about 4 months ago when my CEL first came on I replaced one of my cracked elbows(car would die and read lights, used a basic elbow for Autozone..) now the CEL light hasn't gone off yet and i am fine at red lights but in park i get the rpm reving thing.
Are there other elbow hoses besides the one i replaced? How many vacuum hoses should I have?
Do you think replacing it with a basic elbow instead of buying the Ford Motorcraft kit is the problem(seemed to work for the past 4 months)