Hello all;

I have a 2000 Explorer, 4.0 V6 SOHC w/ 135K miles.
All of a sudden it has an idle issue that's driving me nuts and the dealership can't fix. It has been in the shop 4 times for this problem so far.

It accelerates and cruises great, but when I come to a stoplight, the idle goes down to 900, then suddenly drops to 600 and idles rough.
The "Check Engine" light is NOT lit.
There is no hesitation, backfire or any other running problem.

I have had plugs and wires, PCV valve, IAC valve and MAF sensor replaced.
Technicians have checked for vacuum leaks and intake air gasket leaks and have found nothing.

I can "power brake" it and smooth it out some and even turning on the a/c or defroster boosts the idle and helps a little. Shifting to neutral or park does not raise the idle like previous cars I owned.

I only drive this car back and forth to work, about 1000 miles a month, and I'd like to make this Explorer last at least 200K miles. We just got a Ford Escape and I do not want another car payment right now!
I love my Explorer other than this idle problem!


Thanks
LLMatthews@aol.com

 

Since there are no codes I would try changing the fuel filter and verify that the fuel pressure in within specs.

 

The fuel filter has been changed within the last year.

 

Identical problem with my 02 with the same number of miles. I've replaced plugs, wires, fuel filter, MAF and IAC, and ran sea foam through it (last resort). I took it to a mechanic that says he cannot find it because he can't reproduce it. I do have a CEL though that shows Bank 1 lean. Mechanic says the computer shows that all O2 sensors are working within spec. I cleaned my old IAC and put it back on and it seemed to help some. The mechanic said that the Autozone brand IAC is likely the problem now and could be only slightly off. I hate to go buy a Ford IAC, but that may be the next step.

 

I had the Ford dealership repalce the IAC, so it should be Ford.
I'm beginning to wonder if it's the IAT. Coming to a stoplight, the RPMs will gradually drop and hang at about 900 until a complete stop, then it drops to 600 and starts to miss. I also wonder if its the tranny sensor.
I am also wondering if my CAT is starting to go bad, as I can feel a miss through the steering wheel when I first start up.

 

IAT? Not sure what that is.

 

According to my Haynes manual, it's the Idle Air Temperature Sensor....

 

Thanks. I just wasn't familiar with that term.

BTW, I tried something last night on a hunch. I first sprayed out the butterfly in the throttle body and cleaned a lot of soot out of their with a paper towel. While doing that I noticed an adjustment bolt inder the arm of the throttle linkage (the wire that pulls the butterfly open). I was told by one person that the throttle position switch may have a worn spot in it that would cause a hesitation, but their experience was at highway speeds. I thought, maybe mine may have a worn spot at idle speed and lets it stick at too low of a point. I gave the the bolt about a half to 3/4 turn to force the throttle position slightly up and it stepped the idle up just barely. If this seems to work, it may be the throttle position sensor that is causing these problems. I don't know if it would throw a specific code for that in that low range or not. Just experimenting.

 

Experiment failed.....I just spoke with my wife and she said that the CEL came back on and there's still a problem. Back to the drawing board.

 

You did give me something to think about. I was thinking of asking the dealership to check the throttle body and the TPS.
I do not have any CEL or fault codes, and I almost wish I did.
It seems to run fine until I come to a complete stop at a stoplight. It's supposed to idle around 900, but it drops to 500-600. I can't tell if it's a miss causing a low idle or a low idle causing a miss.
Correct me if I'm wrong, but doesn't the PCM put the engine in a different "mode" during idle vs. cruise or acceleration? It's almost as if the PCM is getting the wrong signal...

 

I don't know about the idle modes. It makes sense though. On all my other vehicles, the idle speed goes up a little when you put it in park. That would be a different mode as well.

It seems as though this problem is discussed a lot, but I can't seem to find a thread where anyone says they found a solution. Surely not everybody is just living with it.

 

I had the same problem with my Explorer, Problem is the o -ring seal under the oil/ vaccum seperator under the intake manifold, just follow the pcv valve that is mounted to a hose all the way under the intake manifold. Your going to have to remove the mainfold and the seperator to get o the o-ring. Make sure the seperator is not cracked before you assemble it back together. The wear & extreme heat will sometimes crack them. Make sure you replace the pcv hose too. The vaccuum is escaping through that seal thats why it runs like if it is missing and it doesn't idle good.

 

Thanks. I will definitely mention it to the mechanic.

I am not mechanically inclined enough to do it myself, so I'll have to take it somewhere. Is that a big/expensive job?

I was really afraid that it was something major, like a fuel injector, valve, or timing chain. I have 135K miles on it, and I hate to think that the timing chain is about to give up....

I had them put a new PCV valve on it. They had to order it, and it came with the hose assembly, so that should be taken care of.

I had also though of the intake gaskets, but the tech said that they have a spray that they use on the area, and if the spray is not "sucked in", they assume that those gaskets are good.

They said that they tested for vacuum leaks and didn't find any. Wouldn't an oil/vacuum separator leak show up?

 

I spent less than $150.00 in parts, did all the labor myself, thiers no way you can spray a liquid to check for the leak since the manifold is over the top of the seperator, I happened to find the leak by pulling on the PCV hose and hearing a loud hissng sound, at first I thought it was the hose, but after I check out the hose and it was ok, I then came upon the seperator, I then notice it was kind of loose, I removed he clip that is suppose to retain the seperator and pulled it outward, the o-seal was cracked and broken causing the air vacuum leak.

 

Cool. I'll check it out.

If it is a vacuum leak, I have no idea why it accelerates and cruises so well. The only time I have any problems is after it warms up, the idle drops after coming to a stop. When I first start the car, I can hold the steering wheel and feel an intermittent miss.