I found my old posts from Oct. 2000 where my 1999 F-250 Superduty (gas 5.4L) refused to run without keeping the gas pedal depressed. I ended up taking the truck to a Ford dealer where they replaced the Intake Air Control Valve which solved the problem. Two years and 60,000 miles later I now have the same problem with the EXACT same symptoms. I'm looking at replacing the IAC valve and wondered if others have experienced this same problem. I am getting 12.5 volts from the PCM to the IAC valve (which appears to be correct) but to remove or check the IAC valve on this truck requires one to remove the throttle body to get to the part which is not a real quick job. Anyone have any thoughts? Thanks!

 

Today I replaced the IAC valve located on the backside of the throttle body. This was a tough job as there was no way to work underneath the cowling so I had to remove the throttle body which took about 1 hour. Put on new IAC valve and new throttle body to manifold gasket and I'm back on the road. Interestingly, resistance checks did not indicate problems with the IAC, but problem must have been in the mechanical plunger portion. Visual inspection of old IAC valve did not indicate problem either but again, the symptoms were identical to previous problem in 2000 that was solved with the IAC valve being changed out. Only had $50 in parts as opposed to $220 + for Ford to do job.

 

The older IAC's used to always have problems with deposits collecting inside them. This would usally cause low idle problems. We would usally fix this by removing the selinoid from the plunger and housing. Would then use carb cleaner or brake cleaner to flush out the mechanical part of the valve. Would lube with a little wd 40 and work the plunger by hand several times to make sure that it moved freely . Would blow out all excess lube and then replace selinoid. Would happen most with high milage engines. PCV used to vent into manifold upstream from IAC and would tend to make it collect deposits pretty regularly. I would clean the old one up and keep it handdy as a spare.

 

That's a good idea, but in looking at the old one it appears the plunger housing is crimped over the solenoid and is uanble to be dissassembled or rather reassembled. There is a black **** on top that turns easily - what is the **** for?

 

That **** is the self-cleaning feature. All you do is turn it and the IAC cleans itself.


I really don't know what it is.

 

You could still probably do a good enough job cleaning it with the electronics attached. Mine has the selinoid attached by screws into a flange. The mechanical part is pretty indestructable, you can flush it out and still get it pretty clean. they are just so sensitive to collecting dirt and it really starts to effect performance when they get clogged or don't move freely.