Our 2005 Focus with 2.0 Duratec engine and automatic transmission and 186,000 miles has developed an issue where, after it has been sitting for several hours, stalls right after starting and won't idle unless a foot is left on the gas for several minutes. This happened a few times last fall but started acting normally when the ambient temperature fell below freezing over night. Now that over night temperatures are in the 30 to 50 degree range, it has resumed this stalling issue when the engine is cold. There have been no codes and no check engine light. Once the engine has warmed up, it idles fine.

Yesterday, I removed and cleaned the IAC (with MAF sensor cleaner spray) after the car had sat unused for about 6 hours. The car started right up and idled correctly. The temperature was about 42 degrees. It then was left unused for about 15 hours. The temperature was then about 35 degrees. When started, the stalling issue was back.

Could the IAC still be the problem and need to be replaced? At least it is in an easy to reach location. Does the Duratec engine have 2 temperature sensors and one of them be bad? The temperature gauge works normally. Someone suggested the MAF sensor could be bad or dirty. Is that possible with these symptoms? Is there a way to test these before replacing them? I don't want to spend over $100 on parts and still possibly not have the issue resolved. Any other ideas?

 

First the vehicle has over 185,000 miles, and we have no idea of what kind of service it has received .
A lot of things can go wrong in those miles.
.We could keep throwing parts at it until we hit the 100 dollar mark and if we hit it great , if not , now, we will invest the 100 dollars and have some tests done to help determine where the problem lies.There could be a few reasons for this to be happening and the shotgun approach sometimes works and most times doesn't.

A good place to start would be to have the computer checked for any codes. A lot of places will do that free of charge hoping to sell you some parts.
Not all problems will illuminate the check engine light but will still store a code in the computer.So far all it would cost was your time.
Interested?

 

I have a mid range code reader, a bit nicer than what I've seen used by local auto parts stores. It has no stored or pending codes.

It receives regular oil changes. It also got a new set of spark plugs during the winter on a day when the weather was decent.

Other than having to replace the alternator three times in the last two years, It has been pretty reliable.

 

Did you also clean the throttle body or wherever the AIC resides? Pull the connector off the MAF and see if the problem goes away.I would also check fuel pressure since borderline pressure often shows a symptom on a cold engine.Has the fuel filer been replaced recently? Your engine uses a fuel injection pressure sensor, is the vacuum line attached to it in good shape? Is there fuel in it?
If you can get a scan tool which can give you live data, you can look at sensor signal voltages and fuel trims to logically track your problem more efficiently.

 

Thanks, Raski, you have given me some direction that I find to be helpful. No, I didn't clean inside whatever that is that the IAC is bolted to. There was a thin layer of dirt inside the IAC but I would not have called it gunked up. It has been over a year since the fuel filter was replaced which means a little over 10,000 miles since it was replaced. I am surprised at the idea that a vacuum line issue could cause this when the engine is cold but not when it is warm. I will look into your fuel pressure suggestions.

I am curious about the idea of removing the connector from the MAF. Whenever I have done that on other cars, the engine would not run well at all. If disconnected, should I expect the engine to idle correctly when it is cold?

The engine does not miss or run rough when cold. It preforms normally other than a foot must stay on the gas until it warms up to keep it from stalling.

 

A typical code reader is not sufficient to provide the info necessary to verify what may be suspected.

A scan tool that can provide what is called data stream info is what is required here.
The figures when cold compared to when warmed up most likely would provide the info to make a worthwhile diagnosis.
Until that is done , you can continue replacing good parts and hoping you hit the cause. If you know someone who has a scan tool and can obtain the data stream info for you then post that info here. We should be able to offer a worthwhile suggestion or two to get to the root cause of the problem. Can you do that?

 

I will work on that this week.

This morning it was 25 degrees and the car had not been started in 20 hours. It idled fine right away. After driving it for half an hour it was parked for about 3 hours. The temperature had risen to 35 degrees. It wouldn't idle when started until it warmed up.

I can see how this could get complicated.

Fortunately, I haven't replaced any parts yet.

 

A scan tool with the ability to display live data can give sensor output signals which are fed to the computer. Many of the sensors are ignored during open loop operation(cold engine). Air flow information from the MAF, ambient air temperature sensor and the coolant temperature sensor. Example, if the outside temperature is 25 degrees(f), you don't want the computer thinking its 65 degrees because of incorrect sensor information. That may not set a code unless the sensor value is well out of its parameters.The engine wants more fuel when cold and a vacuum leak or fuel delivery problem will lean out the mixture and show a symptom when cold but can operate fairly well when warmed up.

 

I know that it has been several months since I talked about this. I have 3 Ford mechanics scan the engine after sitting overnight and all of them said that the readings appear correct. None of them would give me a printout to share here. So I did something that I rarely do, I replaced the IAC without proof that it was faulty. The car now runs fine and has been fine for the last 4 months. Go figure. Now we have to wait for real cold weather again to be sure.

I believe that the big problem was that if you didn't see a problem within 30 seconds of starting a cold engine, it would take many hours of sitting before having a another chance.