When I went to leave work today I started up the truck and it died right out. I had to keep on the pedal to prevent it from stalling. Once i got about a mile away i was able to let it idle, but the idle was very low and it flucuated constantly from 400-500rpm. It did this in neutral, drive, and park. When i got home i started it up a few more times and it did the same thing everytime (low idle jumping from 400 to 500-600ish). What could this be? Does the 5.4 have a idle air control switch or sensor? Any help would be great.

 

Christmas night last year, we got into the Expedition to go home and it started very roughly and just as soon as I took my foot off of the gas pedal in order to press the brake and put it into gear, it stalled. I tried to start the motor 5 times and same results. I got a new Borg Warner Idle Air Control (IAC) valve at O'Reilly Auto Parts for $73.43 and 30 minutes later (the next day) I had it fixed. I probably saved $150. If this sounds like your problem...

1. Disconnect negative terminal from battery(5/16"). Two reasons, safety, and the engine computer has to be provoked into calibrating the new IAC to work with your engine. Disconnecting/reconnecting the battery will accomplish this.

2. Unbolt the three bolts (10mm, I think) that secure the plastic "4.6 or 5.4" cover to the top of the engine.

3. It's on the driver's side, looks like a silver cylinder (1" dia. x 3.5" long).

4. Unplug the two-wire harness from it.

5. Unbolt the old IAC (two bolts, 8mm) and remove the IAC and the old black mounting gasket.

6. Bolt the new IAC in its place. Don't forget the new gasket (or reuse old one)!

7. Plug the wiring harness you unplugged in step 4 onto the new IAC.

8. Put 4.6 or 5.4 cover back on.

9. Reconnect negative terminal to battery.

10. Start engine and let idle for fifteen minutes (Don't touch the accelerator!) to allow the engine management system to learn how much voltage the new IAC needs to perform it's job.

I borrowed this info from another post. I think it was on another forum too.

 

cleaning the iac valve may work as well, it worked for me.

 

Kailor,

Thank you for the great write up. Do you know if the IAC on your 4.6 is diffrent than that of a 5.4? I don't see any silver cylinders near the throttle body. I did take the IAC motor (i belive) off the side of the throttle body and cleaned that and the shaft. It didn't act up the rest of the day, so i don't know if that was the problem or not. Thank you very much for the advice, I may go to napa and order a new IAC valve just to be safe.

 

The V10 has the same problem and I cleaned mine. Have not had this trouble with the Expy 5.4 yet but will clean first.

 

I cleaned my IAC last year, about 30K miles ago. It still idles just fine.

 

Cleaning is an excellent and inexpensive alternative to replacement. What did each of you clean your IAC valve with?

If your looking at throttle body cover from front of vehicle, it's at right rear. It's more than just a silver cylinder, there is a module or something attached to it. Wish I had a picture to post. Good luck.

 

i doused mine with a generic electric/contact cleaner

 

This forum is such a great resource! The other half barely made it home yesterday evening with the engine at first refusing to start and then constantly cutting out. Searched the forum and learned that the problem was probably the IAC valve; went to the local O'Reilly's and bought one ($55) and spent a couple of hours this afternoon removing the old one and bolting in the new one - starts and idles just fine now.

I followed kailor's excellent instructions posted above. My additional 2c:

1) My IAC valve was on the left hand side as you look at the engine, hard up against the firewall (1999 Exp EB 5.4).

2) The top 8mm bolt was fairly easy to get to but the bottom one needed just the right length extension for a 1/4" drive socket to fit and get leverage. The good news was that once started both bolts backed out easily using just my fingers (note that you'll need fairly small fingers to do this).

3) I removed both bolts before unplugging the electrical connector as it was impossible for me to reach the connector beforehand. The plug clicks positively into the socket on the IAC valve so you need to depress the 'bottom' of the connector in order to release the locking tab. Be very careful you don't lose the cable down the firewall once it's unplugged - my cable had very little slack available so I moved very slowly and deliberately when extracting the IAC valve so as not to touch the cable and cause it to slide down and away from its normal position.

4) Similarly I was very careful when moving the new valve into position for the same reason. I simply reversed the procedure and plugged in the connector (you should hear or feel a click as the tab locks) before installing the top bolt first followed by the bottom bolt - don't forget the new gasket which comes with the valve.

5) Do the 15 minute idling thing as kailor suggests and everything should be hunky-dory.

 

someone who actually uses the search (besides me, of course), and on there very first post too!

you, sgtpilot, are a good man (or woman, perhaps).

 

still a man last time I checked!

 

After using the search, this seems like the fix for my problem. As soon as the temp gets out of the single digits, I should be able to fix my problem.

 

patch, is that you?

-brian

 

Replaced the IAC on Saturday.(25 degrees!!!) Hardest thing was getting the battery cable off I put on. Took me 20 minutes with a $53 part from Autozone.( plus tax for the governor.) -8 degrees on Sunday afternoon and I just reached in and turned the key.