Originally Posted by '99F250

Hi guys,
So I've had a misfire in my '99 V10 for a good week now. The day after I noticed it I took 7 coils off and cleaned the contact surface and put some dielectric grease on them. I didn't have all day so I just left the 3 that i couldn't easily get at. It seemed to solve the problem, until just a couple days ago I was driving and I started to notice the thumping and pretty soon it got worse and worse. That evening I was coming home from work and I had only driven a good mile and it was gone again. So while I was driving I put my foot down and gave it some load and nothing, no misfire. It had been really bad when the truck was in overdrive and I gave it a little gas, just enough to put a load on the engine. Tried that and still no misfire. And now today again it is coming back. Talked to a guy at the local Ford dealership and he said check the coils for moisture. How could moisture develop in there so quickly? I pulled them out last Saturday, and they were all free from water, just a good coating of grease. Although some did have some crusty black crap on them (which I cleaned off). As for the other 3 coils, they didn't seem to have a problem after I cleaned the other 7 so I guess I have kida ruled them out for now. Anyone know what's going on?

Originally Posted by '99F250

If anything went bad wouldn't it send a code? I have had no check engine light throughout this whole process, and yes the light does work. What is really surprising me here is the fact that the misfire comes and goes. This morning I drove it a bit but it started misfiring after 5-10 minutes of warming up and 15-20 minutes of driving.

Originally Posted by '99F250

Bit of an update, it stopped misfiring for quite a while, but then it snowed again and it misfired worse than the first time. Also, I bought an Ultragauge, a digital gauge that sits on the dash, it also reads codes. When it misfired real bad the second time it threw a PO300, when googled I found that it meant a misfire in multiple cylinders, not necessarily staying in one particular cylinder. Now I'm not saying that snow causes the misfire, but it's a pretty big coincidence that both times it misfired was driving in snow. I've also been in contact with a Ford tech that lives down the road and he's also baffled. We pulled some coils that I had pulled, along with one in the very back and all looked good. Pulled a plug and it looked brand new. They only have approx. 20k on them. Now I know I know, we didn't pull all of them, fact is it wasn't misfiring when I had him look at it, I actually couldn't even get it to misfire. Drove it for a good 2 hours straight and nothing. Then out of the blue I drove to school last Monday, in the snow, and bam, she misfired at idle even. Never did that before. That's when it threw the code. And now it hasn't misfired since. Has anybody ever had this problem on their truck?

Originally Posted by Pocketlint

P0300 is a general code, it really doesnt say much. I would go to an auto zone and see if you can get them to scan it and they may be able to tell you which cylinders have misfires stored on the truck.

Check and make sure your wiring at each cop is good nothing is chafed or broken, if all looks good I would pull each plug and check it, and if it looks suspect replace it, spark plugs are fairly inexpensive ( have you ever replaced all your plugs?
And see if that cures the issue, if not then might be time ) and I would buy one Coil On Plug pack and pull one coil on plug pack off of a cylinder and put your new one on and see what happens with that cylinder, if all seems good put the old cop back and then pull the next one off the next cylinder and then put the new cop on and repeat till you find the one that is giving you an issue, but I would check all my plugs and the wiring to each cop first

Originally Posted by '99F250

Wiring is something I haven't checked yet, I'll try and get to that sometime soon. My main problem is that it rarely actually misfires, at least enough to plug it into a high end OBD scanner/computer. It's always at the wrong time haha! That's what the tech did, he had a computer that monitored all 10 cylinders. But that does me no good unless it misfires, which is the frustrating part of this whole thing.

Originally Posted by Pocketlint

nothing in the stored codes to indicate what cylinders had the misifire and the count of misfires? odd.

Originally Posted by DavidT.

Pay a tech that knows what they're doing to go on a test drive with you with their scan tool plugged in until it misfires. Ford has one of the friendliest Mode 6 data setups that will tell exactly which cylinder is misfiring.