Fast idle

[Jobert]

Anyone know why my 2002 V8 XLS is suddenly fast idling?

I drove it on the interstate for maybe 15 miles on Sunday and when I stopped and shifted it into Park, it began to idle at about 2500 rpm

When I shifted it into Drive (or Reverse) it went down to normal idle (~800 or so).

I let it cool down for 2 hrs or so and when I started it up, same thing.

The throttle cable isn't stuck or sticking, and the plastic thing is resting against the screw normally, so I assume it's not a linkage problem.

BTW, that screw is a stud and has no visible means of "adjusting" it. There's no slot for a screwdriver nor is there any place for an allen wrench.

The vehicle had been gradually increasing in idle speed for 3 or 4l days prior to this incident, but only maybe 1200 rpms or so. This is waay too fast at 2500 and I can't figure out why it's gone up.

Could it be something other than my linkage? (like a MAF or injector or other problem?)

Thanks for any help.


UPDATE: There's a sticker that I missed under the hood that says:

This vehicle is equipped with electronic engine control systems. Engine idle speed, idle mixture, and ignition timing are not adjustable. See Powertrain Control/Emissions Diagnosis Manual for additional information.

Also, I saw a 2009 post by Soupdaddy that said he'd had that problem before but corrected it with a 'puter reset (disconnect negative battery cable) so I will try that:

http://www.explorerforum.com/forums/index.php?threads/2002-4-6l-fast-idle.254870/
I'll also sniff around for other posts on the subject.

 

[Number4]

You may try cleaning the throttle body. Remove it and spray it down with TB cleaner and scrub it with a tooth brush. Check out all the components attached to it as well, for cleaning.

 

[Jobert]

Okay, I may have solved my problem -- if only for the moment. Time will tell so I will update things later on and let you know how it's doing.

Long story short I did clean the IAC valve as per SyberTiger's thread -

http://www.explorerforum.com/forums...-the-iac-valve-2002-2003.339793/#post-2868726

I'm not sure that helped, but I did it. It obviously needed doing anyway. I did NOT clean the MAF but I likely will do that as well.

The real "solution" seems to be what I did today. I followed the 11-step procedure to clear the PCM here -

http://www.explorerforum.com/forums/index.php?threads/how-i-fixed-my-rough-idle.399499/#post-3241852

When I started it back up, the fast-idle situation was gone and it was "re-learning" things.

I think it's still re-learning things so I'll update this post in the future. As of now it's back to idling at ~700-750 rpm.

UPDATE: Now basically 9:00 PM in New Jersey and I drove it to the supermarket. Have now put 8.8 miles on it and when I got home and put it in park it idled steadily @ ~650 rpm for several minutes. So I'm hopeful.

 

[gtyates]

Make sure your coolant level is at the correct level. If low it can make the engine run a bit warm, and then the computer raises the idle to help cool it off better. Just experienced this on my '05 Sport Trac. If coolant is low check for a leak at the thermostat housing..

 

[Jobert]

I now have 56 miles on it (don't drive it much) and all still seems fine.

That is to say that it's not "stuck" in fast idle. It may still be learning and sometimes it does idle somewhat fast @ ~1200, but after it warms up it always drops down to idling smoothly at ~650 in Park. Sometimes I have to shift it into Drive to get it to do so, but it seems to always return to ~650 in Park. I say it may still be learning because it occasionally does that "rough idle" up @ ~900 or so.

But so far it always seem to return to a smooth ~650 in Park. You'll recall that I said it had run "rough" since I got it in August 2015 with a spat-out spark plug.

I'd say that it might be a good idea to make a short jumper wire and perform the 11-step procedure that I linked above "periodically."

Like maybe every 6 months or 1 year.

Or as required.

One other thing I noticed is that before I cleared the PCM by doing the 11-step procedure, I noticed that there was a distinct "clunking" sound when I slowed down to maybe 10 mph or so. That worried me cuz I don't want no stinking transmission / transaxle problems and it was happening all the time for several days prior to clearing the PCM.

But since I cleared the PCM, I don't hear it anymore. Since "PCM" stands for "Powertrain Control Module", I assume clearing it may have also cleared that problem.

 

[Jobert]

Just to update things, I now have 256 miles on it (don't use it much) and everything is fine other than it idles rough when I first start it and sometimes also when I'm driving it.

But no fast idle once it warms up and no powertrain clunk anymore.