OK guys, I have a 2000 X V10 and am having an intermittent high idle condition. I have searched the forums and found some useful info but nothing that addresses this issue. Here's what I've done. New IAC, found PCV valve hose leaking-replaced also new valve, found another vacuum leak-repaired, tested TPS and that was fine according to the specs I found. So here's my problem-upon starting engine occasionally "stumbles" then roars to life idles 8-1100rpm. Drives well till stopping at an intersection and idles 1100-1200 rpm.(lots of brake) Can pull into parking spot place in park and will idle up 1500-1800 rpm and then only drop to 1200 or so. I have checked everything I know. ALL these idle conditions are INTERMITTENT. (and yes I did check for codes "0" ) There is no loss of power. Any ideas appreciated. ( i'm still thinking TPS but.......)

 

Have you tried adjusting the TPS? I believe it should read below 19 percent at idle. Mine is at 17.2 percent at idle. If it's a TPS (intermittent) part failure then an adjustment would do no good. You can really only adjust it if the bolt holes are 'overbored' by the way.

 

I attempted that but there is no adjustment on this one, just round holes with no room to spare.

 

I drilled out the holes a tiny bit on mine to adjust it. I would try it and bring it down a hair, it can't hurt. I couldn't visually tell on mine that I drilled out the holes. If a smog inspector was able to notice it then it would fail as tampered or modified.

Not related to what I'm saying but here is some diagnostic info.
Part 1 -How to Test the 4.6L, 5.4L Ford Throttle Position Sensor (TPS)

I'm suspecting an intermittent TPS failure. An adjustment wouldn't help if this is the case. Really hard to diagnose. Note the conditions (engine and IAT temp, engine run time, throttle opening, etc.) then try to duplicate while testing again. If you can get a cheap scan tool/code reader that has engine data then you could be watching the data stream during the condition. Look for anything that stands out by reading your TPS data during different normal activities, as a baseline, then compare the data when your having the problem.

 

The TPS should never require adjustment, don't screw with it. The PCM "recalibrates" it every start cycle so you're just spinning your wheels.

If your system is OBD1 instead of OBDII (check label underside of hood), the operating software is much more restricted in its self-diagnostics.

Have you ruled out throttle linkage and throttle body mechanical concerns?

 

Thanks for all the input guys. It seems as though we're all on the same track in regards to the TPS in one way or another. With 204K on the truck I think I'm going to go ahead and replace the TPS. It's inexpensive, I just didn't want to get into throwing parts at it in hopes something would work. I have checked the throttle linkage and the throttle body shaft-no slack or play. Thanks again, I post my results when I get it figured out.

 

Perhaps they were referring more to a sticking throttle cable vs something loose in the linkage. I had an f150 that I had to put my foot under the throttle pedal and pull it back sometimes when it got stuck. Also make sure you don't have a Toyota floor mat under your pedal causing it to jam.

 

Sounds like a vacuum issue to me. Any correlation between brake pedal use and idle issue? Check function of check valve on booster pipe. May want to eliminate booster as an issue to. Any new issues with brake effort?

 

So, I installed a new TPS-no change. Started retracing my steps and got to the throttle body. I had "cleaned" it as part of my trouble shooting and when I say cleaned I mean I remove the air intake and sprayed it down with carb cleaner even though it didn't look that bad. Well I feel pretty dumb at this point. I again cleaned it, this time very thoroughly. From the closed position all looked well, when I opened the butterflies WOW what buildup. I am happy to say that it has been trouble free the last two days. Thanks to all for you advice!