I have a Fiat Stilo (1.6 petrol) that since new has had what sounds like a hole in the exhaust, but only at certain times. When the car is accelerating there is a gruff roar coming from under the car. When the car warms up, this gets much more boomy, sometimes sounding like a ripping sound. There is a type of 'mesh' that connects two parts of the exhaust together before it goes into the front silencer box, and it seems to be coming from here. If the engine is revved while still, the front part of the exhaust leading from the engine to this mesh moves, probably why the mesh is needed so it is flexible. The problem I have is that the boom isn't always there. Sometimes the car can glide along almost silently, and then the boom can just start up again later. Also, if I rev the engine while still or in neutral, there is no boom, it only happens with the engine is under load. I've took the car several times to the dealers in my area, and all are adamant that there is nothing wrong. They drive it a short distance and check its ECU, and give it back. Also, as it won't do it unless its under load, there is no boom when they stick it on the ramp and rev it. It doesn't seem to be a problem with the engine - the car doesn't really seem to loose power, it just gets noisy. Obviously as this mesh is connecting two pipes, it cant be airtight, so could this be the problem? If I had a proplem with a leak or misaligned pipes, wouldn't it do it on every occasion (which it doesn't)? Would an exhaust place be able to check for a problem if it wasn't making this boom on the ramp? I'd love to strap up the joint so it is airtight, but obviously I cant think of anything that I could use that would not melt or go on fire!
Could anyone point me in a direction please? With the dealers refusing to look further at it I'm stuck. Sorry for a barrage of questions.
Thanks Jerry