So, I've got a 02 Disco 2 w/ 89k miles. I recently started getting a misfire once the truck heats up. Ran the codes, p307 and p300. changed the plugs and wires with magnecor and bosch platinums, still getting the misfire. Pulled the plug 7 wire and placed a plug on it to check the spark. It has spark, but it was relatively weak compared to the other plugs I pulled and did the same test on. I was thinking the head gaskets prior to this, but that would have no bearing on the spark obviously. Also, I am not losing any coolant or running hot. Again, this misfire only begins to happen once the truck is warmed up and especially under load. I am thinking possibly coil pack, but don't want to just start replacing things with no good reasoning. Any help is appreciated.

Thanks

 

Before you change anything, wait till it gets dark and with the engine running, lightly squirt some water on that plug and entire length of the wire looking for sparks.
If none found, mine money would be on a failing coil.

 

I did try that, but that cylinder 7 is way in the back. Hard to really get in there, but I did my best and no luck. Any other tests recommended?

 

Perhaps you misunderstood DiscoMike. He gave me the same advice, and it was absolutely telling. What he;s asking you to do, is wait till dark, fill a spray bottle with water, while the engine is running, spray the wires - the part of the wires that you can see - from the plugs back. It sounds like you're trying to spray the coil, which is not necessary.

In my case, the plugs, the wires and coil were shot. Same cylinder misfiring in my case. Swapping out the coil packs did the trick.

HTH,
Steve

 

Hey Steve, thats what I did. Did you have the same symptoms? Misfire once it heated up or all the time? Thanks

 

Yup. If you spray the wires, and you don't see any arc, then they're probably fine. Just as a point of reference, most on this board (these guys know their stuff, btw), will recommend 8MM Magnacore or STI cables. Stock, I believe, were 7MM.

My truck would skip a bit when I first started it up, but definitely got worse, quickly, as it began to warm up. I took it off the road it was so bad. My SES light was blinking all the time, and the codes it threw were P0300 (multiple misfire) P0307 (misfire cyl 7). Have you pulled your codes? If not, you should, and post them here. Guys way smarter about LRs than I am will steer you in the right direction.

 

yep, those are the codes I have.

 

I would be betting on a failing coil buddy. But you can follow the directions of the others and wait till darkness. Are your plugs wet when you take them out?
Dud you use any dielectric grease in the boots when you changed the wires?
Please check to verify that all plugs are plugged in on the coils and check the electrical connection on the coil.

 

I've done the spray bottle in the dark thing prior to posting. Plugs are dry. Double and triple checked to ensure the boots are on, but I did not use any dielectric grease.

 

Try some on the spark plug boots end and see what happens if its still doing it then you can bet on a coil. If you can afford to change both if them while your in there then do it.