Hello,

I have a 2004 Discovery, it has 128,000 miles. I performed a lot of maintenance when i purchased her and she has ran flawlessly for the past 30,000 miles, except for a crankshaft sensor. It received new magnacore 8mm wires and plugs 5 years ago. I have an ultra guage and the truck has never ran hot in my ownership.

Two days ago I was towing my boat, around 3,000 pounds in all, and 10 miles from my house my cel began to flash and i experienced rapid power loss and shaking. I drove it around half a mile to safety and turned it off. Codes were as follow P1300, P0307, and P0304. I towed it and the boat home.

Today I did a quick assessment, drained the oil with no coolant present and no metal on my magnetic drain plug, all plug wires seem to be properly seated.

Any ideas why 2 cylinders on opposite sides of the engine would begin misfiring at the same time?

My next step is to clean the MAF, any help would be great.

Thanks!

 

Bad ignition coil, 4 and 7 pull off the same coil. You can swap it left to right and I bet it follows the coil to cylinders 8 and 5.

 

Sounds like it could certainly be the MAF. I have not found cleaning to do much on the hot wire style MAF, but cleaning can't hurt. There's a reasonably priced Bosch MAF available on Rock Auto (or parts geek?) that I ended up going to.

Try the simplest things first. MAF, Pull #4 and #7 plugs, check your air filter (shot in the dark, but I'm sure a super dirty filter could cause a misfire).

To my knowledge a flashing CEL is usually for a "Potential Cylinder Damaging Misfire." Not to scare you or anything, but I'm pretty sure it has to be more than just a minor misfire to cause the light to flash. I've only read that, I do not know that for sure. Someone more knowledgeable can correct me.

I had my #3 fuel injector fail and spray fuel wide open. I had a P0300 and a P0303 until the cylinder was about to hydrolock and the light started flashing. I got lucky and shut it off and did not damage the motor. Again, not to scare you, but certainly find the cause before doing any driving.

 

Thanks for the response guys. Here is plug #4. It smells strongly of gas.

 

Not going to seriously rant here, but that plug in the picture aka a Bosch 4X Platinum Plug has got to be the worse plug you could ever put into a Rover V8!!!!!!!!!!!

The center electrode is even with the outer insulator and it can very very very very easily get fouled up by carbon deposits and cause misfires. I would HIGHLY recommend ditching those Bosch plugs and going with a set of NGK Double Platinum/Iridium plugs or heck even a set of Denso, or Autolite Double Platinum/Iridium plugs. You're probably smelling fuel on those plugs because they are in fact not sparking well enough to ignite the fuel.

 

Champion double-platinums are OEM and have served me well for ten years.

I doubt it's the MAF.

It could be the coil, but since cylinders 4 and 7 are paired in the truck's wasted spark system it could also be one of the two wires.

Where in Charlotte are you? I have a set of Magnecors a friend removed from his truck several years ago. You're welcome to try swapping them in for your #4 and #7 wires if you want to try that.

 

Thanks for the info on the plugs. Once i run this down ill probably change them out.

So one of the wires on 4 or 7 could go bad and that would cause both cylinders to misfire? I am near Southend and I'd be glad to try that.

 

I think @Extinct's suggestion of coil packs is worth investing since #4 and #7 are on the same coil.

 

PM sent to EHGIII

 

Sheesh - I had the same experience a few weeks back on the 2003 Disco towing the boat as well. The truck new to me, so was in the process of getting rid of the gremlins anyway. All of a sudden, started mis-firing and SES came on. When I took it in, the code was for the purge valve, so checked all the connections, cleaned the Purge valve, etc. SES went away, but still getting misses.