Land Rover Repair: 3.9v8 efi on lpg-misfire,followed by backfire through airbox :(, air flow meter, rotor arm

Question
Hello
I have a problem which im finding difficult to solve.When my engine is warm and under load i.e. up an incline,or pulling out of junctions, i have a nasty misfire occuring,which sometimes leads to a backfire through the air box.this only happens when the engine has reached normal temperature. after some advice i changed the plugs,leads,distributor cap,rotor arm,and air flow meter.I have now been told by someone else that i could have either a valve problem or the timing could be out.as it only happens when the engine is warm could this narrow it down at all?
I appreciate any advice on this matter.

Thanks,Karl

Answer
Hi Karl,

its quite possible that you have an exhaust valve problem.  It is common to have carbon deposits build up and the exhaust valves begine to stick. The only fix is a valve job (about $2000 or so).  Symptoms are much like what you describe.

Best of luck,

JohnMc