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My 2000 Ford F150, 5.4 l 4X4 with cab (88000 miles) has developed an odd habit of engine missing (missfire) that happens about once every 3 months... I hobble home with it missing, park it, get ready to take it in to the shop, then drive it there and doesn't missfire at all! The first time I did leave it there at the shop and they drove it for about 20 miles (no missing), check the plugs and wires and fuel filter and all ok... no diagnostic when they checked the computer brain.
In the past I have had a wiring problems (I can't think offhand what that part was called, but part of the spark plug from what I understand) on two of the cylinders (two different times) and was easily fixed (the current problem acts just like the wiring problem).
Any ideas on this? Very frustrating... hobble home with at least one cylinder missfiring, then get up the next day and acts like nothing has happened!
It starts to miss after it is warmed up.. say about 10 miles of driving or so. I don' think it is the COP (coil) as I have already had two replaced and when they go bad it seems to show up on the diagnostic.
This truck has done this twice now... missed bad on the way into work the first time about 3 months ago.. the tech checked it out and could find nothing wrong. Drove for another three months without a miss, then a couple days ago after about driving 15 miles it started missing badly (to the point where you would swear it was going to die) but was able to hobble home. Let it sit a day with the intent of taking it to the shop this morning and not a single miss all the way to work (about a 13 mile drive).
the iac is right behind the throttle body.you can take it off and clean it with throttle body cleaner usually.check the pvc hose,especially the rubber elbow that goes into the back of the intake,they are bad for rupturing,right in the 90 itself.you said they checked the plugs but at 88000 miles it is getting time to replace them (my 02$ anyway)hope this helps you, good luck
I have had two COPs go out in the past... the engine missing is exactly like when a COP goes bad... the main difference here is that it does not trigger the Engine light and the engine missing goes away after letting the truck sit overnight. When I had a bad COP it would not go away till it got fixed.
I think the spark plug change is a good idea as I am a little old school (learned my engine mechanics on the old 300 straight six (78 F150)) - an engine that was easy to work on. I will check the other hoses/valves though.