I have a 2000 Discovery II with about 90,000 miles. Last week it started sputtering and the service enginge soon light came on. I ran the code as well as searched the forums here and confirmed it was a misfire. I replaced all the spark plugs and wires. One of the plugs (plug 7 to be exact) had stripped threads- probably from the service guy I had do the last tune up! I used a thread chaser and that seemed to work. I also had to replace the adapter to the plenum and the hose from the coolant resevoir to the throttle body because they were cracked. Everything seemed to go back together fine; then I reset the codes. It started up fine and performed well during the test drive. The only thing is there seems to be a repeating "pfft" "pfft" "pfft" coming from mid-engine possibly on the right side. It reminds me of the way a lawnmower or gocart sounds - like the ones at Disneyland. It is not very loud -- but I know it wasn't there before this all started. My first thought was around plug 7, but the noise is coming more from the center of the engine. Any ideas before I start backtracking? Thanks so much for your time and help!!!

 

Check the seal of the stripped plug first then check for a cracked exhaust manifold/loose head pipe connection.

 

So, I re-tapped it, sealed it...and now it runs like a champ! No noise whatsoever! Thanks so much!!!

 

That being the case, chance are it will blow out on you at some point cause there is not alot holding it in so be prepared.