2000 windstar stalls; how to check IAC

It stalls occasionally, and according to my wife, only at idle (usually when coming to a stop). I suspect the IAC, and have taken it off and try to check it. There is 12V at the harness (with the key on); and 11k ohms on the solenoid, which Haynes says is correct. That's as far as their diagnostic goes, but since there's 12V available I should think when I plug it in I should see the shaft move, but it doesn't. I want to know if it should b4 I spend $100 on a new one. BTW, the interior was 'sooty', but the shaft was free to move, spring was ok, and I tried to clean it up. Next day or so will tell if it acts the same, or better.

I don't know about here in the Windstar Forum there are posts specifically for the IAC, but I know there are posts on this in the Taurus Forum. From memory, to test if the IAC is operating properly, start it, then with foot off pedal, turn steering wheel stop to stop. If it acts ok, not trying to stall, then the IAC is ok. IF it stalls or near stalls, then it's not working as it should. Another electrical test in addition to what you did is to measure from the disconnected pins at the IAC to its metal body for resistance to be sure it isn't shorting out. You should have 10k ohms or more. Your other readings and tests were right on.

Does it behave the same wether the engine is hot or cold?
Does the van idle OK in Park or Neutral? And does it change when you put it in gear? Any difference in idle while the brake pedal is depressed or released with the vehicle stopped?

Does it behave the same wether the engine is hot or cold?
Does the van idle OK in Park or Neutral? And does it change when you put it in gear? Any difference in idle while the brake pedal is depressed or released with the vehicle stopped?
I just cleaned the IAC and there is not a lot of improvement, however it idles fine in park/neutral. When in drive it fluctuates between 500-1000 rpm and is very rough idle.

I just cleaned the IAC and there is not a lot of improvement, however it idles fine in park/neutral. When in drive it fluctuates between 500-1000 rpm and is very rough idle.

Welcome to the forum!

Disconnect the harness to the MAF sensor and see if it runs better. Give it a good clean with MAF cleaner and see if it works fine, if it doesn't then replace the MAF.

Best regards,

Oscar.

Thanks, I'll try it. I'm also getting the same codes most others have reported for the 2000 Windstar (171/174).

Sound like a vacuum leak. Warning: if you disconnect MAF sensor and it idle better, it still could be a vacuum leak because air can bypass the MAF and reduce airflow in MAF, thus fuel in injectors. Especially at idle. So if it has a vacuum leak, fuel mixture will be more lean with MAF connected.

Best way to diagnose this problem, is with a vacuum gauge at an manifold port (eg: EGR vacuum intake port). Normally it should be steady from 17-22 mm Hg. If it's lower than 10 mm Hg, it's a big vacuum leak.

It could be also an EGR or PCV valve stuck open.