IDLE Air Control valve

[Lift]

Ok ok i been on this problem for a while now i just finally took the time to figure it out. Heres the problem: Start it up hot or cold or normal w/e my truck idles at 1800 to 2000. Then lowers to about 1600 slowly. Also it bogs every 45 seconds like goes down and goes back up. So This is what i did. I checked my c02 censor it was good i even cleaned it. That didnt do crap. ok So then someone told me Oh hey you dont have a barometric pressure sensor. Didnt get one yet but i will. Im sure thats not the problem tho but it will help. so I thought maybe it might be my TPS so replaced it. unplugged it while the engine was running and plugged it back in. Boom 1100 rpms But Trun off the engine and turn it back on back to 1600. Hmm so then i thought of this funny idea hey lets unplug the idle air control sensor with the motor on Whala 550 rpms-600rpms doesnt bog down up and down anymore. But if you unplug it while it bogs it kills it or it will keep bogging. I beliave my IAC is Bad Im really excited i think i got it please tell me if im correct. Im really hoping i am. If i am i willl replace it asap! haha


Maybe i will post a video of it running and me unplugging the IAC. But not tell tommorow its dark.

 

[Lift]

anyone?

 

[TrexMex]

Dude you're describing the exact same problem I had a year ago. Truck was going up and down in revs when idling. I first tried just to clean up the IAC valve and that worked for a couple of days and back to the problem again. I ended up replacing the sucker and 1 year later I'm a happy idler

ALSO, clean up your MAF sensor really good because the high revs are usually indication of a dirty/faulty MAFsensor. There is an article in the Tech Library on how to do it.

 

[Lift]

Dude you're describing the exact same problem I had a year ago. Truck was going up and down in revs when idling. I first tried just to clean up the IAC valve and that worked for a couple of days and back to the problem again. I ended up replacing the sucker and 1 year later I'm a happy idler

ALSO, clean up your MAF sensor really good because the high revs are usually indication of a dirty/faulty MAFsensor. There is an article in the Tech Library on how to do it.

i knew it! well im going to replace the IAC and i already bought mafs cleaner and cleaned it a while back. You know it really helps when your going to school for this stuff =D.

 

[xentris02]

i had the same problem and my truck was even throwing iac codes and turned out to be tps. it would only happen when it was cold out so it took me last winter and this fall to figure it out

 

[Lift]

I replaced my tps didnt do a thing. I even unpluged it while it was started then plugged it back in it brought it up to 1100 rpms but still bogged and when i restarted the truck it went right back up to 1600. I unpluged the iacm with the engine running and it dropped the rpms to 600 and stopped bogging. Eather i got a bad computer or the module is bad.

 

[TrexMex]

I replaced my tps didnt do a thing. I even unpluged it while it was started then plugged it back in it brought it up to 1100 rpms but still bogged and when i restarted the truck it went right back up to 1600. I unpluged the iacm with the engine running and it dropped the rpms to 600 and stopped bogging. Eather i got a bad computer or the module is bad.

I really wouldn't blame it on the computer... take out the IAC valve, give it a good soak in carb cleaner, rinse and install... it might be stuck. If that helps go ahead and replace it.. it won't be long before it gets stuck again.

 

[TrexMex]

OH and BTW I believe idle RPMs are ~900, but that might only be for manual transmissions; will need someone else to back that up..

Wouldn't hurt to check it, though...

 

[Lift]

I got a 4.0L 5sp maunul. It should not be at 1600. It was probably running on such low rpms when i unpluged it because it has nothing to tell the engine what to run at. So if i replace it or clean it it should be around 800 i beliave.

 

[Lift]

it died when i unplugged it. the 3rd time i started it i was reving it up to keep it alive

http://www.youtube.com/watch?v=vnWU9yq1ZTE

 

[Earl43P]

Looks like it's working to me.

http://fordfuelinjection.com/?p=39

I'd suspect a vacuum leak, but I couldn;t hear any hissing in that video.

 

[Lift]

no vacumm leak. and its idling way to high

 

[TrexMex]

no vacumm leak. and its idling way to high

Try removing the valve from the truck and give it a good cleaning, it might be stuck

 

[Lift]

Try removing the valve from the truck and give it a good cleaning, it might be stuck

ok

 

[Lift]

i removed it and cleaned it. The engine still bogged and the idle went down slightly. Im going to replace it. If that doesnt fix this problem can not having a barometric pressure sensor do it? i dont even have one. When the previous owner did a motor swap he forgot to put it in.