Hy guys ,

Geez , this missing motor is a real pain . Let me start at the beginning , I bought a 99 expedition last year and decided to give the motor a pressure wash and after , it missed like crazy , sounds normal huh , well I checked every connection on every coil pack , changed the plugs ,and it did not help . i called ford and they said that it was because I washed it . Well , after about four days it seemed to clear up and the service engine light went off soon after that and evrything was cool . i decided to not wash the engine anymore after this mishap , though i have done this with every one of my cars with no prblem except for drowned distributer cap once in a while . Okay , now its 6 months later and I was driving around yesterday and it started its missfire thing again . It went from a partial miss to a dead miss , ya know it would be intermin miss for a while , to a dead miss at idle . As of today , it missses bad at first start up , to a intermintent miss as it warms . When fully hot it almost goes away except for a miss everyonce in awhile , and then occassinally it will miss bad . Okay , so I went to auto zone yesterday and had the code read , it says missfire on # 6 . So , I got out my trusty meter and scoped the coilpack and it metered fine , motor was cold , and also checked the injector too. It also ohmed out fine . This is the wierd part about these motors . When running , I can unplug every coilpack and make the motor miss severe and when I plug it in it smooths out agin , this is on evry cylinder . I measured the ohms ,primary and secondary on evry coilpak on the truck and they all measure the same , but yet I still have a miss, What the hell is the matter with this truck ???? I have used the noid light on evry injector plug , there all workin , used the led test lamp on evry coil pak plug and evry thing is working properly . What gives ?? Is there a main plug/harness that is possibly getting wet and if so , where is it located . This is really depressing me as my chevy buddies are laughing about it , and I really believe the ford products are still superior . I have a feeling that it will go away by itself , but would like to find the problem , Can any ford techs out there give me some advice on the matter ??? when it says missfire on # 6 and yet the parts check out , what do you do ??
Is # 6 the second one back on the drivers side , or Am I checking the wrong cylinder ?? Any help on this would be greatly appreciated and btw , this is a great board . Also , I was not driving in wet conditions , the weather has been dry round here for awhile

Thanks ,
Jeff

 

Try replacing the spark plugs. I know it sounds too simple but I have seen it time and time again. Also use only motorcraft platinum plugs. I have seen many vehicles with a miss come in that just had a set of aftermarket plugs installed. The cyls are numered 1-4 on the pass side and 5-8 on the driver's side. Good luck

 

Okay , after leaving it in the garage last night with a dead miss for sure, I know , I left it cool and then restarted it before I went to bed , it seems worse when the engin e is cold , it was a dead miss . I started it this morning and the miss was gone , I mean completely gone , so much so that the service engine soon light turned off after about 2 hours . That makes me believe it is a wet /bad wire connection for sure . Does anybody know where the pcm wiring harness plugs in , it could be getting wet . I guess I should be greatfull that its runnin good , but somehow I think this will happen again , its happened twice since I owned it . Thanks for any help offered !!! Oh , btw , I am using motorcraft
platinums , just put in a set about three months ago .

 

You could also have a bad boot on the coil pack. Try taking out the coil and inspecting the boot for any white spots. I think if you got water in the PCM connector you would have more problems than one dead cyl. Hard to believe the water only got on one pin in the 104 pin connector.