OK guys here's the story:

Car is a 1999 S40 2.0T Manual

When accelerating light to heavy throttle the car makes a noise when it comes onto boost.

This noise is very hard to describe, it is not very loud but sounds like avery fast rattle, kind of like if you put a couple of extremely small stones in a tin can and shook it around.

It is not related to engine rpm but will only happen under boost.

I have not experienced engine detonation before but I'm running out of ideas of what this noise could be. If it was detonation what could this be caused by? If it was an O2 sensor or something else that was the problemsurely it would throw a Check Engine Light?

The car still seems to boost fine and feels like it hasn'tlost anypower (although this problem has been there since I purchased the car so I wouldn't know any different).

I've already checked the obvious and looked for loose hose clamps etc etc. Another thing is that I can distinctly notice the smell of fuel if I park the car in an enclosed space and come back30-60mins later.

If you guys have any suggestions it would be much appreciated.The car will be going on the dyno in a few days with an air/fuel meter stuck up its rear end just to make sure it's not a faulty O2 sensor that's dumping too much fuel in.

If it is a faulty sensor is there anywhere I can buy a cheaper replacement (I'm in Australia), as the volvo dealer wants $AU400 which I feel is a major rip off.

Sorry for the long post.

Cheers,
Kirk

 

Have it diagnosed at the dealer. Tanking a risk on a guess will usually cause you to spend more money in the long run. If/when it is diagnosed you can then look into fixing the problem possibly on your own or/and with aftermarket parts.

 

Try a new set ofspark plugs.

-take care to be the appropriate for your car-

 

Be careful with the car, you must check your local mechanic or any mechanic... Because theres a posibility that the engine will just fire up or burn out...

 

Hello Kirk,

Greetings from Narita, Japan.

Detonation/knocking is generally caused by incorrect ignition timing or wrong octane-rated fuel (I believe most Volvos require premium, though some people have been using regular octane fuel and never have had problems). Are you using regular octane fuel (87-89, depending on the standard, Europe seems to have higher octane numbers and even 90 seems to be considered "regular")?

Ensure thatthe problemis detonation/knocking, before you spend AU$ on unnecessary repair. Also if you don't like visiting the dealer (though sometimes it pays to go to the dealer, as they have specialised equipment & database on common problems). In the U.S, the national automotive technician's license is called ASE Master Technician, and in Japan, it is referred to as the First Rating Technician. Check to see what the Australian certificate/license for automotive technicians and make sure that theperson who works on your car is appropriately certified.

Good luck,


JPN