Can anyone help with suggestions to fix the following problem. I have a gas converted clk every now and then it missfires switches over to petrol and is completely down on power and missfires and back fires through the exhaust. If I turn of the engine and re-start the problem dissapears for a while but then comes back.

The problem also ocurs if run on just petrol and usually happens under heavy load or hard accelleration. Any advice would be much appreciated

Steve

 

Post some codes if you have any.