96 Windstar rough idle

My 96 Windstar with 150k miles is idling rough.

Idle revs (normally around 700 or so) will drop down to 400 every few seconds.

It only happens if the car is in drive and I have my foot on the brake, for example when in slow moving traffic.

Turning on the A/C will fix the problem. This is OK in summertime, but I am not looking forward to winter :)

I have recently had the fuel injector cleaned.
Also have recently had the spark plugs & wires replaced.
This has been going on for some months now (i.e. not just a bad tank of gas).

Any help or suggestions appreciated!

-Lou

I had a similar problem and it turned out to be the Power Steering Pressure relief valve wasn't working properly. Just waiting to find an old unit to replace.My van 96 with 185K would sometimes stall when you turned the wheel at a stop while in drive.

I had a similar problem and it turned out to be the Power Steering Pressure relief valve wasn't working properly. Just waiting to find an old unit to replace.My van 96 with 185K would sometimes stall when you turned the wheel at a stop while in drive.

Interesting. So far I haven't experienced that particular symptom, touch wood.

Another piece of information: the problem also goes away when the heat is on, the temperature is set all the way to blue (cold) but not on A/C
and is blowing through defrost (up so it hits the window).

From reading this message board I am starting to suspect either the IAC or maybe a vacuum leak.

My 96 Windstar with 150k miles is idling rough.

Idle revs (normally around 700 or so) will drop down to 400 every few seconds.

It only happens if the car is in drive and I have my foot on the brake, for example when in slow moving traffic.

Turning on the A/C will fix the problem. This is OK in summertime, but I am not looking forward to winter :)

I have recently had the fuel injector cleaned.
Also have recently had the spark plugs & wires replaced.
This has been going on for some months now (i.e. not just a bad tank of gas).

Any help or suggestions appreciated!

-Lou

I know it sounds silly, have you replaced the fuel filter lately???

I know it sounds silly, have you replaced the fuel filter lately???
That's a good suggestion.. I have all but ruled out the fuel system because my mechanic did an overhaul of that recently including cleaning the fuel injectors. Also, if it was the fuel filter, I am thinking that it would cause problems all the time not just when idling in drive (?) but that's just a guess on my part.

Welcome Ikeeble,

Plug "rough idle 3.8" into the "check this forum" box here. Read, read & read some more. Reference your chiltons, haynes manual. then . . . Reflect, reflect & consider some more. Then post what you've discovered.

My guess is, Intake/vaccume leak. Or some IMRC issue.

We're here to help.

Karl

Interesting. So far I haven't experienced that particular symptom, touch wood.

Another piece of information: the problem also goes away when the heat is on, the temperature is set all the way to blue (cold) but not on A/C
and is blowing through defrost (up so it hits the window).

From reading this message board I am starting to suspect either the IAC or maybe a vacuum leak.
If your defrost is on your A/C compressor is running and your idle compensator is activated. If the IAC is suspected you should be able to place your hand on it and feel it buzzing while your RPMs are fluctuating. Also unplug it and see if it makes any difference. If it doesn't chances are it needs to be replaced. I've been working on one of these off and on when the customer can spare the vehicle and it stalls for them on the first start but won't do it for me. I'm really leaning toward an intermittent vacuum leak like a canister purge solenoid that is sticking or something along those lines. A problem that occurs every day would be more likely to be a loss of vacuum due to a mechanical failure like a seal or gasket. These can be found by spraying the suspected area with WD-40 while the engine is running and you will see a change in RPM. These leaks will usually turn the MIL light on with a Lean Condition code.

Check the Boo switch (Brake on off) The Haynes manual says its a common problem of rough idle.

Check the Boo switch (Brake on off) The Haynes manual says its a common problem of rough idle.

Thanks for that suggestion.

For the time being I am living with the issue by running the van with defrost on or in the summer with A/C on, which smooths out the idle pretty well. I keep going back and forth on whether to sell the van or keep it...

One other thing, a previous poster mentioned that their Windstar died when pulling into a stop, I also have that symptom now, occasionally. It happens when the steering wheel is turned all the way (or almost) and I am coming to a stop. So, when the van is next in the shop I will follow up on that poster's suggestion and have them check the power steering unit.

Thanks,

-Lou

Due to the added load from the compressor in AC and Defrost modes, the engine boosts the IAC signal for higher idle so at least the valve's responding. Being that it is key in idle control and considering the miles on your car, I'd spend for a new IAC and TPS. They are not high dollar, can be installed in a few minutes without need for adjustment, and will most likely fix the problem. There are some enthusiast lists, like SHO forums, that just suggest replacing all engine electronic sensors at 100K to get rid of these intermittent failures.

Make sure after the repair that you disconnect the battery to discharge the system and allow the car to relearn its setttings.
Marc/Atlanta
'98 Windstar
'97 SHO

My friends turned out to be a dirty IAC motor. Sprayed the pintle and the throttle body real good with carb cleaner and the problem has been gone for a year or so. Now if he can just keep the rest of the van working right all at the same time he would be happy, what a POS.