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I have a 1996 3.8L windstar with over 140K miles on it.
The older windstars....like mine....are prone to EGR port clogging.
I have cleaned mine.
The slight miss issue is very common.....and can be difficult to track down....
This is because there are so many things that can cause it.
When my EGR ports clogged....I got a missfire code for cylinder # 4.
The other ports were clogged....and most of the EGR flow went to that cylinder's port.....and caused the missfire. This is the ONLY code that I got. I had replaced the double platinum plugs about 2 months before that.
If you have a miss.... And suspect that it might be a EGR issue.....
1. Locate the vacuum hose that goes to the top of the EGR valve.....
remove and plug it. This will disable the EGR valve from opening.
2. Drive the car.....If the miss is gone....you most likely have clogged EGR ports. ....and they will need to be cleaned....You will want to clean the ports and reconnect the hose.
Please take note that you may get an additional code due to lack of EGR flow whith the EGR system disabled.
A sticking EGR valve is listed as a possible cause of misfire....but seems to be less likely from what I have read on posts here and other places.
Check for vacuum on the EGR valve hose (the one I instructed you to remove). There may be a very slight amount of vacuum....is OK....
But if there is signifcant flow....the EGR Vacuum Regulator solonoid may be sticking....you can spray some 'Sea Foam' into the hose....to clean the solonoid. The EGR Vacuum Regulator solonoid is located on the back of the upper intake manifold on my '96.....you cannot see it...but can follow the hose....and feel it. It may be located at a different place on your 2002...as it has a different upper intake manifold......but you WILL have one. The EGR Vacuum Regulator Solonoid....has an electrical connector that takes an electrical signal from the Computer....telling how much EGR flow is desired....and converts it to a vacuum to the EGR valve. There is also a EGR flow sensor.....called a DPFE (Differential Pressure FEedback sensor)....that has 2 hoses going from the metal pipe that goes from the exhaust manifold to the EGR valve. The difference in pressure between these 2 hoses is proportional to the flow of exhaust gasses through the EGR system.....the DPFE will change this pressure difference to an electrical signal.....and send it to the computer.
Your spark plugs are rated for 100K miles....if all goes ok.
When you have them replaced....have ONLY DOUBLE PLATINUM installed.
As far as I know...only Motorcraft and Autolite have them.
Fuel system cleaning. I did have a slight miss.....finally got bad enough to illuminate the Check Engine Light (CEL).....and I had the code read at autozone (free). I had replaced MANY things prior to this trying to track it down (I figured that I could throw parts at it myself cheaper).
Root cause of my problem was a buildup of crud on the output side of the fuel injector. I found that all of my fuel injectors had this.....even though I kept clean fuel filter and ran fuel system cleaner on a regular basis. The solution was to spray a bit of cleaner on the end of each injector to flush it off......That is...after removing the upper intake manifold...and the fuel injectors to get to the ends of them.
I am told that this is normal for any fuel injector with many miles on it.....The atomized fuel hits the PCV gasses and EGR gasses and the crud is created. I was able to further diagnose by pulling the #1 cylinder spark plug....(the cylinder that was giving me the code this time) and compare it with a plug from another cylinder.....the failing cylinder was cleaner....an indication that it may not be getting as much fuel.
Newer windstarts (Post '98 with the newer upper intake manifold) have a TSB (Technical Service Buletin....NOT a free RECALL) regarding vacuum leaks caused by upper intake manifold gaskets, and bolts....also a replacement valve cover with an improved baffel to reduce PCV liquid (oil) from spraying by into the intake system.
ALL newer cars are subject to pesky vacuum leaks.
Also....The Mass Air Flow sensor (MAF) can become dirty....spraying some non-residue electronic cleaner into the little holes to flush it out will help there. The MAF has a screen.....and a plastic cross piece with a hole in the side facing the air filter and a hole in the opposite side.
The air flows in one hole....and out the other......in the process....it flows over 2 thermal sensors. 1 is heated to maintain a constant tempurature...and the other measures the tempurature....The current flow to maintain the tempurature is proportional to the air flow into the engine.....compensated for the tempurature......
Bottom line....dirt will cause a incorrect reading....and problems.
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