Hi,
My engine sometimes sounds like one of pistons is hitting valves while cranking (very similiar sound to the sound when it's too high gear and revs are too low, but appears only once. Just the hit and motor starts with no problem). It's a very strange sound. For sure none of valves is bent or damaged. Compression is OK and equal through the cylinders. New wires, distributor cap, plugs, fuel filter... Valves are aligned a few hundreds kilometers ago. This sound occurs when the car is a little bit uphill. Have no idea what could cause that.
Any ideas? Thanks
pentaq

 

bump

 

how many miles are on the car? it could be detonation or piston slap. But that would only be a guess from your description

 

125k miles on tacho. What is piston slap?
pentaq

 

well, mine had about that many miles on it when mine developed piston slap. It is where the rod barings or rod baring starts to wear out which makes a small gap between the rod and the crank shaft. SO every time the crank rotates it slaps the piston against the crank In time it gets worse and worse as the gap gets larges from the friction. Plus as the baring wears it leaves a ton of metal pieces to float around your engine causing even more problems.