Rough Idle

Hi,

My 99 Windstar just starts to have some rough idle.

I have changed the IAC (idle air control) valve. However, it does not solve the problem. As a matter of fact, it seems worse than the old IAC valve.

The rough idle is kind of irregular. It is very obvious when I stop. Occasionally, when I was driving, there are some stall but it went away quickly.

The sound of the idle is like "bon bon ". The wait for about few seconds, it is gone. After another while, it comes back again.

What do you think this could be? Could it be the fuel filter.
I changed my fuel filter at about 60K. Now, my van is about 84K.

Thanks for the help.

thsu :smooch:

Hi, my van 2000 windstar 92,000 miles also had a rough idle, I tried a new fuel filter and injector cleaner, and it really only improved a little. I just replaced my water pump and while I had the cowling off I replaced the plugs and wires. My plugs were really worn, the gap on some was almost 1/8" and they were pretty fouled. Also one of my wires, had the insultation cracked and split. With new plugs and wires I can say it is running much better and seems to produce better power.

Thanks for the info.

My windstar does not seem to lose power at driving. The plug may not be the cause. I will check it anyway. I have to admit that the change of the spark plug is really painful for the windstar.

thsu :grinyes:

Ok, an update here.

I think I just solved another white blue smoke problem of my Windstar. However, this irregular rough idle (or misfiring) is still there.

I have changed the spark plugs. The old spark plugs are nearly faulty. After changed the spark plugs, the windstar drives much better. Still, I can feel the little misfiring (or rough idle) when I stop.

Any suggestion?

Thanks

thsu :grinyes:

Check the coil pack for any cracks. This could be your problem if there's an arc in the ignition system.

The rough idle becomes a little bit worse.

How do I check the coil pack? Where is the coil pack?

Thanks

thsu :)

The rough idle becomes a little bit worse.

How do I check the coil pack? Where is the coil pack?

Thanks

thsu :)
The coil pack is located on the passenger side, just behind the plenum. To help, you can follow one of the ht wire, so you will reach it. Maybe it could be uneasy to see an arc on it as you have mentionned that it is irrigular, however a very small arc will give a misfire issue for sure.

So, are you suggesting to "feel" the crack? Is there any other way to "see" the coil?

The symptom is that it only occur at a warm engine at a stop. When I cold start the engine, I do not have this rough idle (or misfiring). Only when I come to a stop for a traffic light, then wait for a few seconds, the rpm suddenly drop from 800 rpm to about 500 rpm and then goes back to 600 rpm.

It is really irregular which makes it not easy to pin down the problem.

Any suggestion will be helpful.

Thanks

thsu :grinyes:

OK, another update here.

Finally frustrated enough. Brought the car the a mechanics. Changed the fuel (gas) filter and spark plug wire. The spark plugs were changed about 3 months ago.

Still, the misfiring issue is there. We then unplug the EGR vacuum line and plug the vacuum line. Well, it does not seem to improve it either.

As a matter of fact, the rough idle seems worse after the change of spark plug wire. The mechanic does not know why either. The thing puzzling us is that the car does not have any hesitation in acceleration or sign of faulty part while the car is moving. It is only when the car stop. The rough shaking comes out.

The mechanic then change a new PCV valve. It seems improve to the original status, which is irregularly rough idle.

Any idea???? It is getting really frustrated now.

PS: I forgot to mention that the car does not have any CEL code or hidden codes.

Thanks

thsu :)

Try a fuel injector cleaning with Berryman's B-12 Chemtool.
Might need a couple of treated tanks of gasoline to clean things up.
I have run into dirty fuel injectors several times on my '96 3.8L.
They get a buildup of crud inside the "end cap" that is at the spray end of the fuel injector.
The rest of the injector and fuel system was fine....I I routinely use detergent based cleaner in a maintenance dose.
The first time, I removed the injectors and cleaned them.
Then, I found out about the Berryman's...which is a solvent based cleaner.....and it seems to help.

The combination of EGR and PCV seems to create a goo.
A Motorcraft PCV valve is a good idea to make sure that you get the correct flow.
Some aftermarket PCV valves, and also old PCV valves can permit too much PCV flow...which ends up pulling extra junk into the intake..