Hi Guys,

New to the forum, and a new owner of a 97 F 250 Light Duty (5.4 Triton) that I just purchased in November off E-Bay. I drove the truck from Denver to WV without any problems at all, but the about 3 days ago I washed the truck (have washed it many times prior to this) came home and the next day the truck starts missing like a nightmare. We plug in a scanner and got the P0307 code and a P0151 code. The engine light comes on occasionally since I bought it and I figured this was the Oxygen sensor code, but I am having difficulty tracking down the misfire on cylinder #7 (P0307). I removed the plug today to inspect it and it is new (the dealership told me so, but I didn't believe them), and the coil pack gives me a reading right at what the book calls for. Plus I get the short burst of voltage through the coul pack receptacle when turning the key to the on position. It doesn't appear to be the coil pack, wiring, or plug, so the only other thing that I had considered was the possibility that I got water into a wiring connector. Any ideas on this one?

 

I had this happen to my 5.4 aswell in the fall. It was the coil on that plug. What seems to happen you will notice a lot of water marks on the coil and it will likley have a crack some where on it. My mech at the dealer took an old inertube and cut out a cover and made a bracket to hold it like an umbrella over the 2 rear coils that seem to have this problem very often so my mech told me. I have not had the problem re occour. It is water that leaks around the hood seal i belive.

My 2 cents.

Josh

 

I replaced the coil, and the plug, and the actual miss is gone. The thing that gets me is the fact that I checked the primary resistance on the replaced coil, the new coil, and a coil from cylinder #1 and the resistance is upposed to be .55 ohms in the book, and i get the following: .54 for the replaced coil, .53 for #1 cylinder coil, and .42 for the new coil? Does anyone think this is proper? Also the book shows the secondary resitsance as being 5,500 ohms, but all 3 coils read 8,000 to 9,000 ohms. I still imagine that I am feeling a slight pulsating in the engine which I did not feel before this affair started, so I am questioning if the new coil is crap?

 

Where did you get the coil. I have seen trouble with aftermarket ones in my area. I am taking mine in on Tuesday to check mine i think i have pop another coil or 2. I am thinking i will say the hell with it and change them all to be done with it.

Josh

 

I got the coil from Auto Zone, and I find the fact that it is way below spec on the primary resistance reading troubling. I am going to check a couple more of the coils on the truck, and then consider taking their junk back if they all run closer to the spec.

 

Sounds like a good plan. I will check mine on tuesday night and post when i get home.

Josh

 

Never wash a modular engine. Before I bought my truck used from the stealer they power wased the engine. I had to have 4 coils replaced before the miss finally went away. The water causes the resistance in the coil to go thru the roof and it will cause a miss. Also moisture in the plug hole causes carbon tracks and spark finds the track by taking path of least resistance which will also cause a miss. Hit ebay for a motocraft coil I picked up 2 new motorcraft cops for 45 bucks. Good luck.

 

Well..... Didn't get a chance to test for resistance but all of my coils were toast. This would explain the weak power and droping fuel economy. It was running ok just a little rough. So my mech took all the coild off changed the plugs (they were not due but while in there) all the coils had cracks almost all the way around. They only had 5 in stock so we picked out the worst ones and changed them. I can see a huge difference even with some weak ones still in. They were not massive cracks but more than enough to make an easy path to ground. My mech was also mentioning of all the failed ones he has tested allmost all were with in the resistance spec. The best way seems to be to inspec with a sharp eye.

Josh