Warren
Q
Last year my 2004 Renault Megane Turbo Spots started to play up with a sorta miss in the engine when at a constant speed. It's not there on acceleration, only when cruising. I have had four mechanics check it, but none could find anything wrong. They changed the alternator and the exhaust sensor, the injectors were cleaned three times, new spark plugs were installed, had the vacuum test and the camera up the exhaust pipe. Don't know why they did that. One said it was a sticking exhaust valve, but that would cost $4000 and it might not fix it! I'm out of ideas. I don't want to get rid of it as I love it, I was also insulted with a car yard offering me $5000 for it. What can I do?
Graham Smith
Ask Smithy
A
Your description of the problem suggests it's not an ignition problem, so changing plugs etc was probably a waste of time and money. I'd be investigating the fuel side of the equation, looking for things that might be making it lean at low throttle openings as you would be when cruising. Is there an air leak that's affecting the mixture strength, or something like that. Having said that, it could be a sticking valve as the mechanic has diagnosed, but I would expect to be able to see that on a compression test. If it is a sticking valve the only to know for sure is to take the head off and physically check it.
