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I recently had my cam belt and water pump changed by a local garage (parts from GSF). Since I got the car back I've been consistently getting lower MPG - almost up to 20% lower (mid 40s on the commute). Also, the power delivery has altered - there is less of a surge up to 3k rpm (only a little less) and much more of a noticable surge post 3k rpm - it will spin the wheels in 2nd on a damp road at this point.

Are the cam belt and resulting behaviour a coincidence? I would think if the belt was a tooth out it wouldn't run at all well.

Is there anything that needs to be done during a cam belt change that might have been missed?

Cheers for any advice.

Lower MPG could be due to a timing issue...also, your car is remapped if memory serves well? If the timing was off mechanically, a remap could complicate matters further as far as power delivery goes. I'd check the timing first of all...

Hope you manage to sort it out as soon as possible

Ash

I thought it was only right to post an update on this - it's been an age....

The issue took a while to diagnose, but Storm Developments found the problem in the end.

I took it back to the guy and he checked the whole lot with my help, but nothing showed up. Then when I took it to Storm they also struggled until they delved in further (an hour's labour got nowhere).

The issue was the belt wasn't tensioned properly. This led to a "variable" timing that differed under load and so on as the belt tried to catch up tension-wise. They redid the belt and it's back to normal now. When the engine was static it all looked OK.

So, £200 lighter and all is well. Told the original garage but I didn't want to press the matter because it's a mate.