2001 Winstar wants to stall at stop lights

[jdrh]

I have searched the forum on stalling at idle and have not found a situation quite like ours. My wife's 2001 Windstar starts and runs fine until she has to wait more than 1 minute at a stop light. The idle will slow down and act like the engine is going to stall. It has stalled on a couple of occasions. To keep it from stalling, she shifts into neutral. Here is the strange part. This only happens during the first 15 minutes of driving in town. I don't recall it ever happening after driving longer than that. The van has 150k plus on it. It has been doing this for months. I checked the IAC and it was clean as new. I recently replaced the engine coolant temperature sensor and that hasn't helped.
Could it be the cam position sensor? I saw a few posts on that causing stalling.

[jbearden84]

Although the IAC looks clean, unless you can verify that it's new, i'd still replace it. They arent that expensive and i've seen many cause that type of problem. Also check for vacuum leaks.

[jdrh]

I will take your advice and replace the IAC valve. Thanks.

[jbearden84]

Yea give that a try. Also dont forget to check for vacuum leaks.

[joeuser742]

After reading this post, a few days later my 2003 did the same thing. It only happened once, I was sitting at a stoplight, the van was still cold. It kind of felt like it was running on 4-5 cylinders. I was thinking it it could be a an injector getting clogged or on it's way out. Another thing it could be is the coilpack.

[12Ounce]

Other "usual suspects" to add to the list:
MAF sensors ... a spraying with proper cleaner can do the trick.
EGR system problems ... not the main valve, but the feedback sensor or sensing hoses. Also the EGR jets may be plugging.
Ditto to IAC and vacuum leaks.
Alternator output Check with voltmeter at idle.
Throttle body dirty ...plate sticking, or position sensor awry.

[jbearden84]

Originally Posted by 12Ounce

Other "usual suspects" to add to the list:
MAF sensors ... a spraying with proper cleaner can do the trick.
EGR system problems ... not the main valve, but the feedback sensor or sensing hoses. Also the EGR jets may be plugging.
Ditto to IAC and vacuum leaks.
Alternator output Check with voltmeter at idle.
Throttle body dirty ...plate sticking, or position sensor awry.

Yep I would try taking a look at all of these things. They are relatively quick, easy things to look at, and with the age of these vans, it probly needs to be done anyway

[jbearden84]

Originally Posted by joeuser742

After reading this post, a few days later my 2003 did the same thing. It only happened once, I was sitting at a stoplight, the van was still cold. It kind of felt like it was running on 4-5 cylinders. I was thinking it it could be a an injector getting clogged or on it's way out. Another thing it could be is the coilpack.

Next time it does this, try stepping lightly on the accelerator pedal with your other on the brake. Normally, if the IAC is bad, opening the throttle plate a little will bring the idle back to normal and you'll know thats what it is. Of course that doesnt always mean it's a bad IAC but in my experience it has alot of the time. If, when you step on the accelerator, the engine does not smooth out, then i would look elsewhere.

[joeuser742]

In my case I think it's a fuel injector. The van was sitting at the light for 10 seconds before it did this. I just got the van not long ago, I have yet to change the fuel filter and put some of that fuel injector cleaner in. I also need to take a look at the coilpack.

[serge_saati]

In my opinion, the most probable cause is a vacuum leak. Because it's very intermittent.
Do this test: next time it happens, turn off engine, unplug MAF sensor to put in LIMP mode, then restart the engine. If the symptoms disappears, you can eliminate fuel delivery and ignition problem.
Then it would be vacuum or MAF problem.
You'll notice if you drive a little bit in LIMP mode that the transmission shift very hardly. So I don't recommend you to drive like that, just idle. Do this test in a parking lot, not in a big boulevard.

When you have a vacuum leak, air bypass the MAF sensor. So unmetered air goes in intake, and your air/fuel mixture is wrong. Also less air pass through the MAF since pressure in MAF is reduced because of leak. When you press on the gas, the small leak don't make a big difference. When you run in LIMP mode, you don't use the MAF data, but TPS and rpm data instead. There's no MAP sensor to compensate for vacuum leak in this van.

You can also visually inspect the MAF sensor, but it takes time to remove it in a 3.8L.

Don't replace parts for nothing, do this test, and test for vacuum if needed.

Do you also leak antifreeze and oil? If so, it could be one lower intake manifold gasket.

When you shift in neutral, there's less load and vacuum for the engine than in Drive or Reverse when you're stopping. Because the torque converter doesn't need to force too much when it pumps hydraulic fluid to the turbine nor to rotate the stator clutch with the fluid. So less load means more available power and better idling.

[jdrh]

Well, I did replace the IAC valve, but it didn't solve the problem. The problem seems to be occurring more often now. I guess it's time to check all the vacuum lines. I haven't checked all the vacuum hoses, because I get a reading of 20 inches at idle. The next time it happens, I will unplug the MAF sensor to see what it does. Does anyone know where I can find a diagram of all the vacuum lines?