Hello,
I own a 2001 f150 with a 5.4L engine and 145,000 miles. The engine fluctuates at idle between 400 and 700 RPM's. Will stall when I let gas pedal go to quickly. Not throwing codes and CEL not on. Runs great while driving. It's when I stop at light or in traffic almost dies. I changed pcv valve and still stalls. If I rev the engine a few good times, "sometimes" it will idle right. How can I tell if MAF sensor is bad. I looked at it and it looks cosmetically ok. Any help appreciated!

 

I would suspect either an idle speed sensor or the throttle body needs to be cleaned. I would get a good throttle body clearer before replacing the idle speed sensor. With high mileage, carbon can build up around the throttle body butterfly.

 

Probably the idle air control valve (IAC).

http://www.oreillyauto.com/site/c/de...2169&ppt=C0018

You can remove yours and clean it, with carb cleaner and see if that helps. IF it does help, either replace it, or keep running the cleaned old one. For some reason, cleaned ones don't seem to last as long as replacing, so that's up to you.

 

Thank you Schraubenzieher and mustang8998 i will give them a try.