'96 Windstar misfires when warms up....

[Repiv]

1996 3.8 windstar misfires. Runs smooth throughout driving range upon start up but when it reaches operating temp idles rough and bucks when driving, no engine light no codes sent. Help......

[taillight]

Sounds like it might be the EGR. Try cleaning it out.

[Repiv]

Also engine pings and gets poor fuel milage.

[wiswind]

As tailight mentioned, it could be dirty EGR ports.....just not bad enough to light a CEL yet.
There is a EGR port for each cylinder, pressed into the lower intake manifold.
They develop a black soot right at the end.....where the EGR gasses meet the oil vapor from the PCV system.
The EGR ports start clogging at the driver's side, Cylinders 1 and 6 first.
The last to clog are cylinders 3 and 4......at the passenger side of the vehicle.
So, these 2 cylinders end up getting ALL the EGR gasses when the EGR valve opens.....which causes a misfire on cylinder(s) 3 and/or 4.

The only way to clean the EGR ports is to remove the upper intake manifold.
Then is is real easy to clean them...as the crud is only right at the end of the port.
I have pictures that show the EGR ports.
When I remove the Throttle body, prior to removing the upper intake manifold, I leave the accellerator cable connected.....I just remove what I need to, to get all the bolts removed, and then carefully set the throttle body to one side.

As you do not mention it, I am guessing that you are not loosing coolant, which would indicate a possible lower intake manifold gasket leak....which could cause a misfire also.

If the spark plug wires and spark plugs are relatively new, I would try putting a can of Berryman's B-12 Chemtool (metal can) into the gasoline tank to clean the fuel system....particularly the spray end of the fuel injectors, which tend to build up some of the same gook that cloggs the EGR ports.
This cleaner will NOT clean the EGR ports, however, as the fuel never gets to the EGR ports.
I have tried a variety of fuel system cleaners, and was directed to this one by my mechanic.
It is the ONLY one that I have found that really clears up the dirt at the end of the fuel injectors.
It might take 2 or 3 tanks of fuel....each one treated with 1 can of the fuel system cleaner.

There are other things that could cause a misfire....but without any codes, doing anything other than normal tune-up stuff would not be called for...as you would just be throwing parts at it.....without really knowing much about the problem.
I have been down that road.
A code will give you a place to look.

[96wWindstar180K]

Repiv
Just went through a heck of a time trying to find a bucking and hesitation problem. It ended up being the fuel pump. If you have a fuel pressure tester one that connects to the fuel rail connect it and turn the key to the on position. Dont try and start it. The pressure should be about 34lbs. Mine was like 12 if I turned the ignition on and off it would pump up to about 25 lbs. The problem was it was intermittent the first time I tested it it was fine. It got worse. No codes either. I brought it to a guy finally to have it diagnosed and he found 2 bad injectors. I replaced all of them. I got them from a place called Fiveomotorsports.com It was $260.00 for all of them 3 year unlimitted mileage warranty. If you cant figure it out find a local shop that will hook it up to a computer and watch things as fuel trim and ignition timing as well as testing of items like the Maf sensor. I spent $108. to have it diagnosed and did the work myself. The fuel pump I had the guy who did the original diagnosis do. There are things that are general maintenace items that should be replace if they havent been. As Wiswin said wires, plugs, pcv, air cleaner, fuel filter. If you have done these tins then I would look again as Wiswin said at the egr port cleaning. I did mine at about 187,000 miles. By the way my van would run fine until it got warm also. Ithough it was related to the coolant sensor that sends info to the pcm. It eventually got to the point where it would hesitate and buck whether it was warm or not.

How many miles?
Another nice thing about having someone put it on the computer is they ca read all the codes in memory. I found a code for brake light switch and Boo switch. As well as communication error with my Abs. All things that wont necessarily light a CEL. Post back if you find anything.

[Repiv]

Thanks for the information. We've got all new sparkplugs, wires and ignition coil in it and cleaned the EGR ports. Didn't fix anything but the check engine light finally gave us a misfire on cylinder 6 code. Replaced cylinder 6 and it is still giving a misfire on cylinder 6 code.

Still runs good while it is cool.