I have a 99 disco II with 76Kmiles on it and keep getting a misfire on Cyl 7 when decelerating from 65 or 70 mph(CEL begins flashing then goes solid) and then cel goes out after a day. The OBD codes are only for a misfire on 7. Also, it seems to run rough around 1500 RPMs but smothes out at 2000 RPMs up. They put it on a scope and everything runs fine. There is bit of oil above the number 7 plug, but wonder if it is arcing to the block, but think it would happen all the time, not just when decelerating. Fan clutch needs replaced, whould that have any effect. They changed all the wires and plugs and same result.....any ideas?

 

A failing fan clutch has no connection with a engine misfire. If they replaced the plugs and wires, and you are still getting a mis-fire code thrown, then the coil pack is suspect. However ---this usually manifests itself with two cylinder mis-fire codes. When you say there is "a bit of oil" above plug #7, what are you saying?---is the spark plug wire boot wet?

this could cause arcing, but only if it is drenched. Pull the wire boot off, clean it with a degreasing agent--along with the spark plug itself and try it. Of course-- you want to fix the source of the oil leak. It is most likely a valve cover screw with a damaged seal or the valve cover gasket.

regards,
Geoman
www.eurotekapg.com

 

It's just a bit of oil....not too much. The oil is just around the socket...very slow leak. Could it be a cam position sensor, since it's happens mostly on deceleration.

 

There is a possibility that it is the cam sensor, but they USUALLY fail outright and prevent the engine even firing up. You may want to check to see if there is any oil that found it's way into the cam sensor connector. I also tell people to do the same inspection on the O2 sensor connectors. We have seen a few where oil or coolant has found its way into this connector which results in erratic signals and fuel mixture variations. Again-- clean those out with a spray electrical contact cleaner and snap them back together.

regards,
Geoman
www.eurotekapg.com

 

Thanks...I'll try that...is that a diy or should I have the shop do it, I don't want to break the sensors....

 

It is simply a matter of unplugging the O2 sensor from the harness at the connector. Easy---and could solve your problem.

regards,
Geoman

 

99% 0f the time your spark plug wires go bad after 70K.I learned the hard way,hopefully I'll save you a headache.Pop the hood open with the engine running wet all around them.If you get any sparks then you found your problem.If you replace them.Make sure you buy some good 8mm wires.I learned that the hard way too.

 

If you are still running the factory wires, it is time to replace them, I would suggest the 8mm Magnacor wire that can be found on ,
http://www.roverconnection.com/ and other web sites.
Mike

 

Wrong! DII Gems will start with out cam signal. It will choose a bank and fire it. Are you refering to crankshaft signal? That would make sense.