I have a BA Ford XR8 with 210000 on the clock. The car is on gas and has just recently started to play up on me. The car seems to misfire when the outside temperature reaches any where above about twenty three degrees C. I have replaced the plugs with new Iridium plugs, had the gas system (Parnell VSI System) serviced. The vehicle idles with no problem and runs fine on petrol. But on gas if I ask the question of it, it will misfire until I get the revs up. Once again it only happens above 23 degrees C. Any ideas? Ford and the gas people have offered nothing.

first thing is these heads are notorious for wearing out the valve guides very rapidly (some as low as 30,000ks)...there were a few changes to the heads made.....what year is yours? and have your heads ever been off?

gas is even worse for valves and guides than petrol.....

The car is a 2003 and the heads have never been removed I have owned the car since 2004 when it had only 20k on the clock.

Apart from this one problem with misfires above 23 degrees C I have had a great run with this engine. When the weather is cold the car runs great.