Truck idles fast momentarily when the clutch is pushed in. This happened about a 1 1/2 years ago at which point I replaced the IAC. Over the last month or so, it started doing it again. Since I bought the "auto store brand" I assumed that maybe it had gone bad, so I installed a new Motorcraft one. Truck started doing it again, but I can't find the thread(s) that talk about other things to check. Can someone direct me to the threads or what else I need to check. I've looked for vacuum leaks and can't find any plus The DPFE sensor has been recently changed due to a P401 code. I also have no CEL.
Thanks

 

a bad pcv valve will cause a high idle, and not throw a code.

 

Thanks, I will check into it. As far as I know it's still the original one with almost 155,000 on it.

 

At 155K, your well past due for a scheduled maintenance replacement on the PCV valve. Check your PCV system rubber fittings, rubber hoses condition & their fit also.

 

Paw Paw, I was actually thinking about that on the way home from work this morning. I am thinking along the lines of replacing all that while I was there.

 

There is a tech bulletin ford put out. I can't rememeber the number of it.
It concerns the 98-2000 rangers. High idle issues when replacing the IAC don't fix it.
Basically the connector on the TPS is jacked up and Ford recommends buying their $80 kit to fix it. The kit has a new connector which you splice into the old cable harness for the TPS.

I had the same issue every 6 months and would replace the IAC for high idle and it always came back anywhere from 3 months to 6 months. I also noticed a pattern. The high idle always seems to come about during wet or humid weather conditions.

After reading the tech bulletin I decided to clean the connector on the TPS and the connector that plugs into the TPS with electronics cleaner. While the connector was wet with the cleaner, I put the connectors together and took them apart several times to help clean the contacts/pins. I let the connector dry for a few minutes and then stuffed the connector with dielectric grease to help prevent corrosion on the pins. Put everthing back together and fixed. No idle issues anymore. After doing this your idle trim might be out of wack but drive it for a couple of days and let it relearn the idle trim. Don't bother unhooking the battery to do this. Just drive it.

 

Did not know about that. Thanks for the info, I'll look in to it also.

 

High Idle TSB 00-3-5

 

I've got the same problem with mine (2000 4 cylinder manual tranny) I was gonna ask about on here. About a year and a half ago or so, I got the same high idle problem when I stopped and clutched, and could also feel the idle surge driving at lower speeds.

I replaced the IAC valve with an aftermarket part which lasted a couple months before starting again. Since it was still under warranty, I took it back and put the new one on which again worked for a couple months before the idle problem returned. I then spent the extra money for the Ford part figuring that might solve the problem, which it did for 9 months, and just last week has AGAIN returned!!!

Greenpus, I'll have to try cleaning the TPS like you described above and see if that helps. I'm at about 120,000 miles and I've not replaced the PCV valve since I bought the truck at about 80,000 miles so I guess that wouldn't hurt either.

If anyone else has any input, I'd certainly appreciate hearing it too!! This high idle problem is really getting to be an annoyance, almost enough to justify that next truck payment!

 

Ford should have replaced the pcv for free at 60,000. That's stated in the warranty booklet for the 2000 2.5. From that point on, the owner is required to replace it every 60,000 after.

 

It's possible the PCV was replaced under warranty, I really don't know. The used car dealer I bought it from said he bought it from a Ford dealer, they used it as a parts truck before selling it. You'd think they kept up with all the maintenance as required, but who know.

Just wondering, if the problem's been with the TPS all along and not really the IAC valve, why does replacing the IAC solve the problem at least for a few months?

I can't say for sure if my problem has only been during wet or humid weather, but I'll have to start paying more attention to that.

 

When I first brought my truck into ford for the high idle, they had no idea what it was and said, it's either the iac or tps. first guess they took was the iac and it worked for a year. after that, i started replacing the iac every 6 months or so for high idle issues and never took it back to ford. I can guess as well as they can LOL.
My guess is when you replace the iac you also bang on the tps cable and cause it to reseat itself and it works for a while. The same thing would probably happen if you disconnect the connector from the tps and reconnect.
Cleaning and using dielectric grease on the tps connector fix it for me and my truck has been good on the idle for over a year now and I'm using one of the iac's that I thought was bad.

 

Ok, so just to be clear, you didn't remove the TPS, you just unhooked it, cleaned the contacts, filled the holes in the connector with the dielectric grease, and reconnected it, right? If that's it, I'm gonna give that a shot tomorrow and will let you know how that goes.

Good to know you kept using the same IAC valve, because I considered trying to take that one back to Ford to see if I could replace it under warranty. I'll try this first before messing with it though.

Thanks for the input!

 

yes. Don't remove the tps just unhook the connector. every tool box should have dielectric grease. I don't buy it from the autoparts stores becuase you don't get alot and they charge to much. I buy it online in the big *** tubes because I like it and use it a lot on my motorcycles to keep the connectors clean and well protected.

 

Just a quick update -- replaced the PCV and hose, no help. My valve did have a Motorcraft number on it, so I'm assuming it was still original. Hose just looked dried out, didn't find any cracks or splits in it.

Cleaned the connector for the TPS as suggested, so far so good. Will now in the next couple of days for sure.