99 Windstar running rough intermittently

I have a 99 Windstar with the 3.8 V6 and at times it will run very rough and make popping sounds when I accelerate. It can run like this for a couple days at a time and then go away for up to 6 months at a time. I can run to the store and it will run rough on the way there and fine on the way home. It never stalls, it just has loss of power and makes the popping noise if under a heavy acceleration. I have added different fuel injector cleaner and it seems to help for a short time but then it can come right back or stay away for a long time. Any ideas?

Have you had a tune up, plugs and wires, replaced? Ford double platnium plugs should be replaced every 100,000kms, I have also seen the ignition coils crack, you will not be able to see crcks unless you remove it and inspect the bottom.

Does the Check Engine Light come on?
There is a TSB for vaccum leaks for 1999 and newer windstars.
Save this link for future reference.
http://leckemby.net/windstar/windstar01.html

I would think that you would get a CEL, but it still could be in the early phases of failing.
Vaccum leaks can be tough to track down.
It can be leaking when the engine is cold vs warm, or vice versa.

There is a Mass Air Flow (MAF) sensor right next to the air filter, and there is also a air temperature sensor in the flexible air hose that goes from the MAF (and air filter) to the throttle body. Both of these have electrical connectors, and they can both be cleaned with a spray of non-residue electronic cleaner. You can buy the cleaner at Radio Shack, and I have also seen it on the shelf at several auto parts stores. You want to flush dirt off the surface of the thermistors.

I have had a tune up not even a year ago. I have 118,000 miles on it and I had the 100k recommended maintenence performed on it. While working on it they told me I needed new plug wires also. I have noticed in the past couple of days that the popping noise is only when the rpms are between 1500 - 2500 then it just sort of sounds like it is running on 5 cylinders.

And yes, my Check Engine Light is on and has been for sometime now. Even when the van is running good the light stays on and when it is running really rough the light blinks.

I had similar problems. It was P0301 - cyl 1 misfire. Sometimes I saw P0304 - cyl 4 misfire. It was clogged EGR ports - 2, 3, 5, 6 clog up leaving 1 and 4 open to get all the dirty EGR air.

Check your codes - Autozone does it for free.

Search EGR ports here. Wiswind has a good pictorial.

I have had a tune up not even a year ago. I have 118,000 miles on it and I had the 100k recommended maintenence performed on it. While working on it they told me I needed new plug wires also. I have noticed in the past couple of days that the popping noise is only when the rpms are between 1500 - 2500 then it just sort of sounds like it is running on 5 cylinders.

And yes, my Check Engine Light is on and has been for sometime now. Even when the van is running good the light stays on and when it is running really rough the light blinks.

Definatlely step # 1 - Get the codes read.

Your problems could be caused by any number of things including - Lack of ignition, too much fuel, EGR flow, clogged EGR ports, Vacuum leaks.........

I wanted to thank you that have responded to this. It got so bad I ended up taking it into the shop. After having it for 4 hours they called me and told me it was ready and it was free of charge. It ended up being a broken spark plug and it was under warranty since they had just put then in last year.

Good deal - it's good to see an easy AND free fix.