2002 Discovery II with 163,000 miles. Starting fine, but idling rough. Service Engine light has come on, and getting the following error codes:

P0154
P0300
P0301
P0306
P1300

 

P0300/P0301/P0306 = misfire faults. Check spark plug wires, spark plugs, or even the coil packs.

 

Do not drive, flashing means misfiring bad. It will ruin your cats... and your dogs if not careful.

 

I definitely check that. I cleared the codes and took it for a quick drive. Codes P1300, P0301, and P306. Seems to be pointing at an issue with Cylinders 1 & 6.

 

Cylinders 1 and 6 are paired in the DII's "wasted spark" ignition system. That means a severe problem on either number 1 or number 6 can trigger a misfire on the other. For example, years ago I had a bad wire on number 6 that also triggered a misfire on number 1.

Here are a couple low-cost things to check. First, wait until after dark and start the engine, pop the hood and look to see if you can see any arcing from the wires for either 1 or 6 to the engine.

If no arcing is evident try swapping the number 1 and number 6 spark plugs with plugs from other cylinders to see if the problem stays with numbers 1 and 6 or if it moves. If the problem moves you have a spark plug problem. If the problem stays you likely have an ignition wire problem.

Also, while you have a couple of the plugs removed doublecheck exactly what they are. Write down and post the brand and the numbers on the plugs. The first time I had a misfire problem, several months before the wire problem I noted above, it was because a mechanic had installed regular, copper Champions instead of the double platinum champions specified for the waste in Sparks system. The copper champions will run just fine for a few thousand miles but get eaten up quickly. For long life, the DII needs to have double platinum spark plugs.

Next try swapping plug wires with comparable-length wires from other cylinders and see if the problem moves. I know that swapping plug wires is more difficult given how tough it is to access the coil.

Finally, I know a lot of guys on these forums change the coils but in my experience, and that of some very experienced contributors here, the ignition coils on DIIs fail rarely.

 

As far as coils dying I've replaced 2 pairs so far in the past 2 years. Latest was my 02 Kalahari with 229k on it. Had P0300, and P0306. Checked the plug and found a crappy Bosch x2 in there! Figured that was my problem, then the spark plug wire crumbled to bits. Replaced the plug & wire. P0300 & P0306 came back instantly. After that I didn't beat around the bush any longer. I replaced all 8 spark plugs, removed the intake manifold (once you do it several times it's really not bad), swapped out both coil packs with aftermarket coils, installed some Kingsborne spark plug wires, and slapped back on the intake manifold. Misfire was gone for good.

You've got 163k on it so if it was me I'd replace the plugs, wires, and coils and call it a day.

Coil packs don't last forever. Eventually the spark gets weaker and weaker until it starts popping misfire faults.

 

Thanks for the replies. I'll start on the basic checks tomorrow, but I'll probably end up replacing the plugs and wires, maybe the coil.

 

+1 on pretty much everything already said. One thing to add... You were also getting a code for your bank 2 sensor 1 O2 sensor, which could be playing into that cylinder 6 misfire. I would try to figure out why there is no signal from that sensor as part of your overall repair.

 

which brand/spec plugs are you going with? curious. i might have to do this exact same job.

EDIT:
im on atalntic british and i see they have the "champion" spark plugs http://www.roverparts.com/Parts/NLP100320OEM seems legit.

paired with the http://www.kingsbornewires.com/Disco...-p/ign-790.htm wires? lol wont be to expensive

 

I'm going to be using those exact wires and plugs. Also it was the ignition wire to 6 causing the issue.

I'm going to go ahead and change all the wires and plugs since I got stuff pulled apart. Really appreciate all the advice everyone threw my way.