OK. I have a 2003 Ford F150 Super Crew with 4.6 V8 triton. Last summer my truck started missfireing. When I checked trouble codes it said had bad COP. So I replaced all 8 COP on truck. Truck ran fine for about a month. Started having the same problem. Misfireing. It wouldn't do it all the time. When I checked the codes again it still said I had bad cop. So once again I replaced the ones that was missfireing. But this did not seam to fx my problem. I noticed last summer the truck would not missfire untill the outside tempurture was above 80 degrees. All winter long truck has run with no problems. Last week when temputures here in Texas went above 85 degrees my truck started doing the same thing. I was intially told that my computer was not working, but when I took truck last summer to Ford Dealership to have them run computer diagnostic they said computer was working fine. Intially thought it might be a wireing issue but i'm told by ford they no longer make the wireing harness for this year model of ford. Was wondering if anyone had a solution to this as well?

I'm wondering if any one has insites on why it would only missfire when temps outside get to hot and why it runs fine in cool weather. What i might check next to see whats going on?


Chris

 

You need to ID the cylinder that is misfiring by either doing a trap as you drive or look at the missfire counts with a good scanner.
At that point you replace the coil and boot to see if the issue clears.
If not, the solidstate switch in the computer could be the cause but only after all other ways are exhausted.
The missfire codes are either 35x indicating a coil primary issue or a 30x indicating a secondary issue.
Pay attention to which shows up.
If you can't get a shop to do these things, purchuse a Scanner such as the Craftsman unit for about $180 and do the trap function and look at the missfire counts in test 53 under non continious monitoring.
It's education and taking the bull by the horns when things don't go right and may be cheaper in the end.
Good luck.

 

I will get another scan run. When they did a OBD read on it last summer I was getting codes like P301, but would get multiple P30X. When a machanic was running it he replaced p301. Then it Poped p302. It did that right down the line till all 8 replaced. Then last summer seams like it was P301. Which is Cylender 1, Cylender 5, and 7 randomly. The COP been replaced 3 or 4 times last summer.
Thats the only codes I was getting. The scanner used would say Primary/Secondary ignition fault. If the problem is the swtich in the coputer can that be fixed or do I have to replace computer?

 

P30x codes are secondary ,not the computer side of the circuit.
Some scanners definitions are misleading.
I would abandon all past history and begin new because the old info is causing you confusion.
Good luck.

 

ok. If i abandon the past history. What do I need to look into. It was over 90 Degrees outside to day. and Truck began to Missfire about 20 mins after driving. AC was running. What should I check for. Where should I begin

Chris

 

On that basis I would say it's a coil breaking down from heat.
A scanner with a trap feature should catch the cylinder causing the missfire.
I can't be any simpler.
The coil is a 'bobbin wound' afair.
It expands and contracts with heating and cooling.
This can break a lead wire at the terminals and make a connection when cold and open when expansion takes place.
See why past history has little value? It's what is happening now that counts.
Good luck.

 

Ok what brand of Coil would you put in there. Cause I have tried Napa Autoparts Coils, and I have used Motocraft brand none have fixed the problem. So what brand would you suggest to use.

 

Use an OEM coil.
What cylinder is misfireing?

 

I haven't checked it on a scanner again yet. I believe it cylender #1. When I un plug # 1 no change in how it runs. But Will get it checked on scanner before I buy COP.

 

Bluegrass have a quick question for you. I read somewhere on this forum that if the spark plug isn't properly seated it can cause a missfire. When I changed COP's last summer I put new spark Plugs in. I used Motograft Pltatnum. If I didn't torque them could that be cause of missfire?

I wouldn't think so but was wondering after read forum under TechGuides and someone mentioned that about spark Plugs.

And one more question. Is the Motocraft plugs say from O'Reilly Autoparts same as ones from Ford Dealership.

Thanks

 

If plug is not tightened enough and lets cylinder pressure blow by the threads, it could be percieved as a missfire due to lower cylinder pressure causing slower rotation time as measured by the crank sensor..
Plugs of the same make and numder are the same no matter who sells them.
Any replacement plug speced for the motor that fits no matter how it's made will work.
Only differences is the longevity from the materials used.
Good luck.

 

I ment to ask is the Motocraft COP's were the same from O'reilly Auto Parts as from the ford Dealer.

Also I found out the spark plugs are to be torqued. I've read alot of different opinions what they should be torqued to. What is the recomened Torque?

 

If the coils have the Oem part number you fine.
On plug torque, you need to know the heads are Alum so you can't crank on the plug endlessly.
The plug seals with a taper against the head.
The threads only hold the plug taper to a tight gas seal.
A wide range torque of 84 to 168 Inch Pounds....not foot pounds.
If the threads are dry and show some resistance coming out then uses some never seize on the new plugs or you can't tell with any accuracy what the torque is doing when tighening.
You should be able to use about 6" of heater hose that fits the plug like a tight boot and hand screw the plug in by feel then do the torque if the threads are clean.
Good luck.