4.6is knocking noise

[danab1987]

Hi i am new here as i have recently brought an estoril blue 4.6is. The car is realy good and drives very nicely but has a few problems that need sorting.

The main one is a knocking/tapping noise that i think is coming from drivers side of engine. It does it while accelerating between about 1500 to 2000 rpm but not in neutral. If you accelerate very slowly or very quickly you cant here it. It doesnt get louder or speed up with the engine speed. The car has lpg and does it alot quieter on lpg but as soon as you change to petrol its alot louder. It doesnt happen when the engine is cold. The other thing i have noticed is that when i got it the noise definitley wasnt there, now i have been driving the car quite hard the noise is there. The last few days i have driven more relaxed and the noise has quietened down alot.

The reason i know it wasnt there when i test drove it is because an hour before i went to look at another 4.6 and didnt buy it becasue that one also had this noise,but louder and did it in neutral when reved to 2000rpm, so we listened for that exact noise when driving this one.

People that have heard it think timing chain rattle so either guides or tensioner or maybe knock sensor but apparently it is alot quieter and not as harsh a knock for that,or maybe hydraulic lifters sticking. All these things i just think would sound the same wether running on lpg or petrol? I have changed the oil and filter twice and hasnt helped,the oil was black but no obvious bits of metal or plastic in it. I am going to try spark plugs when i get chance.

Forgot to say when i test drove the car i didnt try on petrol so could well of been doing it on that,but didnt do it on lpg at all. Half way home i switched to petrol and when i came off the motorway i noticed the noise. The one i brought is on 93k with full service history and has been well looked after, the other one was on 97k with full service history and again looked well looked after.

Sorry for the long first post but the car is perfect but the noise is driving me insane!

If anyone has any ideas would be realy appreciated.

Thanks