2001 Disco Series 2 with 98000 miles. Received P0303 for Misfire, Cyl 3. Did complete tune up. Changed to Bosch 4+ Platinum plugs, Kingsborne 8mm wires. I did not remove the IM to replace the wires...was able to install without doing so.

Idles fine, drives smooth...great acceleration. Cleared code, code came back. any suggestions. Feel free to email me directly if needed - lafrance@salinacountryclub.com.

Thanks folks.

 

What did the old plug look like when you removed it from #3?
What octane gas are you running?
I would do a compression test to make sure you don't have a valve issue, if need to check further I would suggest a leak down test.
Let us know what you find.

 

I could benefit from your expertise. compression test and leak down test, you've lost me. the compression test I can figure out though I've never done one. The leak down test, I've never heard of.....

The #3 plug looked the same as the others. Little rusty looking on the threads, no oil or carbon on it though...no visual evidence out of the ordinary.

Vehicle appears to run smooth, I'm not noticing any rough idle and it accelerates cleanly.

Fuel - 91 or better