Have a 2000 D2 w/96000 miles. No coolant leaks, new front gasket. Just started missing cylinders 8 & 5 - subsequent cat code. New Magnacore wires and Bosh Platinum 4s about 2000 miles ago. Suspect coil (as 5 & 8 are on top of the same bank). Have had MAF codes in the past but not getting them in this instance. Missing can be heard at idle and is evident at low speeds but not noticeable at highway speeds. Have sea foam in tank and ran it through the intake plenum as per service, this seems to have given some improvement.
Don't want to run extensively and damage the cats. Have had cat failure in trucks and lost power. Am not seeing that loss of power now. Would like some thoughts as to possibility of coil pak problem.

Thanks

 

Could be. Did you do the seafoam after the plugs and wires? Did you do the wires AFTER the misfire came up? Something simple and relatively inexpensive is to swap to stock Champions and see how the misfire is then.

 

The plugs are not causing the problem, and if there were a concern, it would be easier to just switch 5 and 8 with 2 other plugs in the engine and see if the faults follow to the new holes.
The Plus 4's are not the problem and, as much as I am a believer in Seafoam, it won't fix this problem.
Did the 2 misfires show up at the same time and exactly what are the other 4 digit fault codes you have?

 

Codes that come up: P0305, P0308. also get P1314 and Random Missfire P0300. Took the truck up to the garage and used a light on the plug wire. No. 5 showed good fire on the device. No. 8 showed no fire. Came back and removed the No. 8 wire and replaced.

Started and still have a miss. Under load (driving) the service engine light comes on and flashes...when the truck is stopped the light goes to steady. The manual on my scanner says that flashing light indicates that the missfire is ongoing, when the light is on steady the missfire is no longer occurring.
Is the missfire only occurring under load?

Reading the codes after driving gives P0305 & P0308, P0305 two to one over P0308. Also P0300 - listed as random missfire on my scanner. No P1314 in short trip.

Probably get in there and replace No. 5 plug wire.

 

Codes: P1300,P0308,P0305,P0308 on last drive of about 2 miles. Truck has obvious miss at idle.
Realized the wires I recently put on are 7mm, ordered a set of 8mm Magnacores-figured to get that out of the way first.
Replaced the No. 8 with a generic 7mm I had in a set in the garage, not much help. Just after doing the work top side also got miss on 4 (P0304 and sometimes see 7 (P037) plus the random miss. Had cleared all before the codes on last drive, they did not appear on the short drive.
SES light flashes.

Interesting note: I found a vacumn leak on hose to top of plenum (secondary air) tightened it thinking there might be some results-nope.

MAF codes have not been coming up since cleaning it and cleaning the connections.

Hmm???

 

New observation yesterday. SES light stops flashing above 2500 RPM, no obvious miss at greater than 2500, drop below and miss starts, SES lamp flashes.

 

Quit driving it with the light flashes, you are going to destroy both of your cats.
Replace the coil, clear the codes and you will be set.
But no more test drives, we knew yesterday what the problem was and cats are expensive.

 

Thanks for the clarification, parts are on their way.

 

Let us know how it goes.