very low idle when cold

[nobodyfresh]

I've searched these forums and read dozens of posts that I thought were the same problem as mine but have not found a solution.

My 2000 Explorer v6 4.0 SOHC has problems idling when it is cold outside. It behaves similar to a carb engine that has a faulty choke. The idle is very low and it stumbles when revving it until about 1500rpm. The problem goes away once the engine reaches operating temperate. This only occurs in weather below about 60 degrees and worsens as the weather gets colder.

I have replaced the IAC, MAF sensor, spark plugs, spark plug wires, and air filter. I do not hear nor see any noticeable vacuum leaks.

Any ideas?

It's getting really cold out and it would be nice to be able to install a remote starter!

 

[fixxxer]

Your coolant temp sensor could be bad, it's very easy to test. http://www.autozone.com/az/cds/en_us/0900823d/80/04/f5/ac/0900823d8004f5ac/repairInfoPages.htm

 

[nobodyfresh]

I think I'm going to bite the bullet and do the 00m12 fix. I have the diesel sounds when it is cold like alot of people and its possible my intake gaskets may be causing this cold idle problem. Thoughts?

 

[fixxxer]

That would be a good place to start, but check for loose intake manifold bolts and any vacuum leaks first before getting too far into it.

 

[Cobraguy]

It sounds like the ECM is struggling with control of the cold idle. The coolant sensor is a good place to start. A faulty or dirty IAC motor too. If no codes are set, this will take some good diagnosis work to determine the cause.

 

[nobodyfresh]

I know the IAC isn't dirty/faulty because I just replaced it. I will check the coolant temp sensor today.

 

[nobodyfresh]

I installed the 00m12 kit today. It went fairly easy and took about 3 hours. I compared the two cam tensioner bolts and the new one is slightly longer which I assume just takes some of the slack out of the cam chains.

Anyways, I think my idle problem is fixed but I won't really know until tomorrow morning. However, my diesel sounds still persist. Interestingly enough, for the past 2 years it only made the sounds on cold starts and lasted a few minutes. Today (before I worked on it) it made the sounds all day! I'm guessing something finally fully broke and I'm going to have to replace the guides and all the other fun stuff

Is this new problem something I should worry about? I won't really have the time to replace the guides for another couple weeks. It's really annoying and crappy sounding but I can deal with that temporarily if I have a nice cold idle. *crossing my fingers*

 

[nobodyfresh]

This morning it started right up and held a steady idle for over 10 minutes in 16 degree weather!

When I first started it I let it run for about 5 minutes and it had no diesel sounds. I had to do something so I turned it off and when I came back 30 minutes later to try it again it started right up and idled smooth but the diesel sounds came back.

Does the diesel sounds suddenly getting really bad yesterday and then not existing this morning but coming back 30 minutes later make sense to anyone?

I really don't want to open the timing chain cover and have to replace the parts in there if I don't have to.

 

[nobodyfresh]

Does anyone have an estimate of how long it would take to pop the front timing cover off and replace the plastic guides that are most likely broken? Also, would I have to remove the intake again?

 

[dawgtown]

My 99 Mountaineer 4.0 has similar problem. It idles bad in cold weather. After about 10-15 minutes it smooths out but still runs rough for awhile. During warm weather it runs like an injector is misfiring. Sometimes it will stall when I stop at a stop sign, etc. Gas mileage is bad. A mechanic replaced the plugs, wires and 02 sensors and cleaned the throttle bottle. He connected it to a computer and now says there is a problem in #2 cylinder. I've spent too much money already. Any recommendations?