ok I have a 1993 F150 supercab with a 5.0 EFI I recently had a strong exhaust leak type sound and rich exhaust smell which turned out to be a broken exhaust manifold tube to the EGR That problem solved!! Yay!! But just before I fixed that problem it started running very rough and missing as well as has a loud whoosh sound from the intake as if it is trying to suck some serious air. If i unplug the IAC valve the whooshing sucking air sound stops imediately but still runs rough and stalls i of course replaced the IAC but no change. I am stumped. I need anyones help who might shed some light on the situation. I appreciate it Thanks

 

Check for codes

 

The engine light is not on and so no codes are present if i understand how it works correctly but.... it runs so poorly i dont know if it would do an accurate test??

 

No codes at all? That means something.

 

what would that mean???

 

No cel doesn't always mean there aren't codes. Scan for 'em anyway. It will test all your sensors solenoids and other electronics instead of just taking readings and may find your trouble

 

Did you disconnect the battery before/ after replacing the IAC? The computer will remember how it was running before and won't adjust sometimes, so resetting it will help it reconfigure how much air to take in for it to run smoothly.

Also, for the "whooshing" sound, check for any cracks or holes in your intake.

Before disconnecting check your codes. Use a scanner or if you don't have a scanner this THREAD will help you.

 

ok ran the codes came up with 22 which pointed towards MAP sensor. through the vacuum on it and it stalls and dies passed about 12 hg so i pulled a sensor from the junk yard and it runs better and smooth now. still slight whooshing sound but now it idles pretty high and it is very slow to come down if you hit the throttle. Meaning bring it up to say 2500 rpm it does not drop down instantly and stays at about 1100 for an idle? Any thoughts.

 

Skid Row

I will disconnect the batter and see if that helps and let you know

 

ok i disconnected the battery then reconnected and fired it up. Still high idle about 1400 on cold engine. Ran it around the block and out on the highway and it still is slow to come down when shifting and or at a stop. When the engine is warm it hangs around 1100 to say 950 rpm at idle Too high! Any thoughts