Land Rover Repair: 99 Discovery missfire, landrover discovery, valve job

Question
Hi John,
I have a 99 Landrover Discovery V8i.(87,000 miles)  My Landrover idels rough and when going up hills or going over 65mph it will missfire or sputter.  When I leave of the gas it seems to catch but is running rougher than normal. The yellow CHECK ENGINE light has been coming on. I took it to my local mechanic who I trust.  He hooked it up to his computer diagnostic.  It is reading a missfire code.  He has changed the plugs, wires, and coil with no progress.  I called the LR dealer they stated with the work I have done it needs a valve job with out seeing the car due to carbon build up .  My mechanic ran Sea Bond? through the engine with no help.  Should I get a OBDII reader to make sure what the problem is?  Should I put a new engine for $3,000 or get a valve job from my local mechanic.  I wonder if the valve job will work? any advise would be helpful thank you very much John.

Answer
Hi Joseph,

it is common that Series II Disco's have the sticking exhaust valve problem anytime after 50,000miles.  It could be your trouble.  If it is the exhaust valves, no amount of additive can help.  

I would have a LR specialist connect your Disco to the TESTBOOK and determine if there are other components at fault.  Idle air valve, MAF, TPS, and some other components can mimic symptoms like the this.  

IF it turns out to be the exhaust valves, a valve job is about $2000 and much less than a rebuilt engine.  The $3000 you mention does sound tempting but that's another concern.

You could ask your local mechanic to run a pressure check on your engine - just in case.

Best of luck,

JohnMc