95 for w-star engine surging

My 95 ford w-star Lx 3.8L enging surges from 600rpm to 900rpm but only when the vehicle is stoped in gear, i.e at a stop light.
Any ideas out there??
Thanks

Hello and welcome to the forum!

Try taking a look at the IAC valve; I'm not sure about the 95 model but it should be located at the throttle body it has a 2 pin connector running to it. It may be dirty or full of carbon and the PCM cannot properly adjust it causing the RPM's surging. If that doesn't helps try cleaning the MAF sensor with MAF cleaner.

Best regards,

Oscar.

Thank you very much, i will post my results.
I took out the IAC it looked to be in very good condition, no corrosion at all.
I haven't got to anything else because i am so busy working.
I will try all of the other helpfull tips this weekend, ''i hope''
thank you .
ps it does serge at any teperature, but only when it is in gear and stoped, or trying to stop/park

Surging could indicate a vacuum leak. A big culprit on these vans is a vacuum leak on the hard plastic tube that resides on the back of the motor on the passenger side. (on mine it's red).

Correct me if I'm wrong, but I believe faulty IAC's usually manifest themselves only when the engine is cold. I had one and thats what mine did. It idles like crap until it warmed up. After that, I never had the problem again. It acts like a choke.

Mark

The IAC can act up at any temperature.
The IAC is more like a mini-accellerator, it opens a path for air to bypass the throttle plate in the throttle body.
The intent is to have the computer (PCM) control the airflow (idle) when your foot is off the accellerator.
The IAC has a small motor inside that drives a "screw" that opens and closes a valve.
It could stick only when cold, all the time, or who knows when.
The FIRST step is to try to clean it, using something like the spray version of SeaFoam or even WD-40......which will leave some lubricant on the threads of that screw so that it moves more easily.

If it was a problem with IAC, it will show different symptoms. It's not the IAC.

It's either a problem with vacuum leak or maybe the MAF sensor is dirty. Or the O2 sensors. That's the most probable culprits in descending order.

Do you have CEL on? (check engine on).