Land Rover Repair: Land Rover Discovery misfire problems, land rover discovery, cat converter


Question
The car is one year old (2002) and has only 10,000 miles on it.  It has been in for service for minor problemms three times so far.  

Just recently it started to misfire and within 24 hours the "Check Engine" warning went on. The mechanic said it was a faulty wire connecting to a spark plug, but everything else looked fine.

My concern is, could the misfire  have caused any additional damage? I asked the mechanic, he said it should not have, but I'm not to convinced. I read in the manual that mis-fire can cause damage to the catalytic converter.  

Thanks,
Lourdes  

Answer
Hello Lourdes.m.caress (?):

Yes, misfires can cause severe damage to your catalytic converter IF driven for extended periods and left unrepaired.  Here is what happens:

Due to the fact that the fuel does not get burnt in the cylinder it gets into the catalyst, which promtly treats it as hydrocarbon emmisions, which of course it is, and burns the fuel. This heats the catalyst up too much, which can get to the stage of the whole thing melting internally. This is obviously not repairable, hence new catalyst required. It has been known for a catalyst to melt, and then solidify in the exhaust pipe, blocking it and making the vehicle undriveable, though this is rare. Hence, if engine has misfire drive on very small throttle openings only until the matter is sorted.

SO,  if your misfire has been repaired quickly and you have not driven months with this misfire condition, you should have little or no trouble. OTHERWISE, you are looking at a ruined cat.converter.

Since you are still under warranty, I would make sure that LR investigates this thouroughly BEFORE signing off on any work.  Only you can tell if the misfire condition was left unrepaired for an extended period...the more fuel unburnt, the more damage to the cat.converter.  The only remedy I am aware of is a new converter.  Good luck trying to get LR to replace this WHILE under warranty.  They'd prefer to wait until just after your warranty expires then nail you for the $2000 job!

Best of luck with this,

JohnMc