Hi all,
I've been reading a lot of posts on this subject, I have done some troubleshooting and wanted to get some feedback from ya'll.

2002 Discovery II 165,000 miles
Replaced head gasket and plugs about 6 months ago
Replaced wires with Kingsbourne about 2 months ago
Replaced serpentine belt a week ago
Ran 44k through when I replaced the wires

2 months ago I pulled the plenum and did the wires myself. Coil pack was very loose, one of the 2 bracket bolts missing. I assume after the head gasket job. I added a bolt, tightened down the coil packs. One thing I did not replace was the plenum gasket because I figured it was only a few months old. It was also a PITA to reseat the intake cover so who knows if I roughed up the gasket. Anyway, car ran fine afterwards for weeks.

engine light came on about 2 weeks ago. Mainly rough idle while parked and in drive or reverse. Misfire can be felt while parked. I bought an OBDII code reader and get a P0305 misfire in cylinder #5. I tried to check the #5 wire into the coil but not enough hand room to see if it was not fully seated. Swapped plugs in #5 but no luck.

I reset the codes, and the car runs fine. To trigger the code I find a steep hill, stop, accelerate quickly and it misfires under load. CEL blinks, then stops and when the car is up to speed it runs fine. I reset the codes and to trigger it again, I have to do something under load.

Plugs are NGK Iridium 2's or something like that. Plug was dry, metal arch was white powder looking. Some carbon on the base.

So that's where I am. Won't throw a code until under a load at low speeds. Swapping wires is a no-go without pulling the plenum again. Whoever designed that aluminum tube running across the back between the engine and coil pack - thank you for blocking access.

I am thinking coil packs.

http://www.roverparts.com/Parts/ERR6566

Thanks!
Jamie

 

For what it's worth - I swapped plug #5 and it only threw a code when I found a steep hill and forced a load. I reset the code. I drove 3 miles to WalMart, no code. Got some Sea Foam and put 16 oz in 1/2 tank gas. I drove about 10 miles with no codes. Mainly trying to get some Sea Foam through the fuel system. I did not climb steep hills but I did gun the accelerator a few times to suck fuel. It did not misfire or throw any codes.

Would a failed coil or wire be intermittent and only under heavy load? Now I am hoping may something fuel related? Maybe starved in that injector under load?

Just still thinking out loud.

 

With just one cylinder I wouldn't rush to think coils.

Have you tried swapping the wire and plug to a different cylinder, reset the code and see what pops up?

Physically inspect the wire and check it hasn't rubbed on anything hot. Sai hot pipes for instance.

Start easy and cheap.

 

Thanks, the problem is I cannot swap wires without pulling off the top. Not sure if that metal tube is called SAI or what, but even disconnecting the hoses from each end, I cannot get enough room to unplug a wire to swap. Wish I could, because I would. I am mentally preparing to pull the plenum off and check things out, but once I have it off, I want to have any replacement parts on hand because I don't like messing with that thing. :-) It is a pain in the butt for me each time I have it off.

 

If you have an inspection camera, stick it in the plug hole.

Worst case scenario would be steamed cleaned piston, meaning cracked block. Maybe check another piston for a comparison.

At least you could rule this out with no real dis assembly.

I've seen 2 motors do this on #5.

Good luck.

 

I don't have one. Will keep that in mind. Dry plug and only intermittent misfire?

 

Do you have a scanner with live data to monitor the misfires? That might help to see if its really intermittent.

 

I just got the scanner and earlier was doing some live data reading. I'm still learning the scanner. I'll see if I can do a live read and see. Thanks.

 

At least swap a couple of plugs, see what happens. Rule something out.
I was able to swap my wires without removing the top. And I used to be. Soccer goalkeeper, i.e. Big hands. SAI was a bit of a pain, but with long screwdrivers, pliers etc.

From the bit you can see the wire looks good? I know you said they are fairly new. My fairly new wire touched something hot, shorted.

Isn't there an iPhone app/inspection camera on a wire yet? I'm off to make one if not.

 

On my scanner I was looking at the rpm monitor. Up and down like an an EKG. Cold varied 100rpm and warm it varied about 50. Couldn't really see misfires.

Code light still not back on. Swapped a plug earlier and still threw a code to same cylinder.

Wires are seated on the valve cover gaskets as they bend around back. I could see touching metal as my wires do rest on metal in many places. When I replaced wires it was hard keeping wires off metal.