Omega Owners Forum
Omega Help Area => Omega General Help => Topic started by: leeh on 21 February 2007, 19:55:50
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hi
i have a 98 2.5 cdx which lacks power , i did have a em fault light on but did not have it checked before it cleared. when the car is idiling its fine but when you rev the engine or drive at 2000+ rpm you can hear a hissing from the end of the exhaust. does anybody know what the fault is.
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Strange one indeed. Partially blocked back box or cat maybe? It might be gas escaping through a blockage of some sort.
Also, the engine management will probably go into closed loop mode at around 2k rpm and above meaning the mixture control is supplemented by information from the Lambda sensor. It could be that a faulty sensor would send the engine excessively lean or rich at this point, however, it wouldn't do so on full throttle, just light throttle, and it would almost certainly continue to show a fault as this is easily detected in the ECU. I wonder if the ECU stores a fault history? Might be worth getting it checked for fault codes.
Could it be a leaky / disconnected vacuum line to one of the dual ram actuators that is hissing? It would come from the front of the car, of course, but maybe the hissing sound is actually from there? This would have the double whammy of affecting engine performance due to incorrect positions of the dual ram valves and also introducing a (small) unmetered air leak into the induction system. I think the dual ram actuator at the rear of the plenum changes state just off idle (from open to closed).
I don't suppose it's the fuel pump making the noise? If this is on its' way out it may be that it's causing fuel starvation as the manifold depression decreases on an open throttle and fuel pressure has to increase to compensate? Could equally be a blocked filter, fuel line or in-tank pre-filter.
All just wild stab-in-the-dark guesses though I'm afraid.
Kevin
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I suspect a blocked exhaust to.....is it from the rear of the car.....in which case its the back box.....and I have seen one that went BANG....
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..and I have seen one that went BANG....
Ouch!
I'm just struggling to think what would actually block it. I wonder if they're lined with wadding that has come adrift. Maybe a piece of baffle could have broken off and lodged against the exit pipes. Can you have a poke up the tail pipes with a screwdriver or something? Maybe you'll feel an obstruction?
Kevin
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thanks guys
yes the hissing is coming from the rear of the car i will check the exhaust tomorrow
lee
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I don't suppose that a snake has decided to hibernate in your exhaust system by any chance? :D
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My car suffered a blocked centre box. Only found out when I replaced the exhaust and the car was suddenly a lot faster.
Seen a few cars where the fibreglass wadding in the back box starts to come adrift and blocks the backbox.
The car will run fine without a back box, doesn't even sound too bad - honest. The problem is you won't easily separate it, I had to peel mine off after splitting the outer pipe with an angle grinder.
Try putting your hand over the end of the exhaust. If all is well and the exhaust has no leaks then I don't think it's actually possible to block the exhaust with a single hand. If you've a partial blockage and some leaks then you'll hear some good quality hissing!
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I don't have this exact thing, but I do seem to have an exhaust which makes too much noise - it sounds like a woodpecker when you rev over 3k (definitely a knocking noise rather than rasping) - and the power can be sparadic at times (actually, most of the time) - is there any test I might be able to do on it, save taking the entire exhaust off..
Some daylight might help.
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I don't have this exact thing, but I do seem to have an exhaust which makes too much noise - it sounds like a woodpecker when you rev over 3k (definitely a knocking noise rather than rasping) - and the power can be sparadic at times (actually, most of the time) - is there any test I might be able to do on it, save taking the entire exhaust off..
Some daylight might help.
Oh yeah, and there seems to be more smoke than I would like coming from it - although I'm guessing this could relate to my cam covers and the oil thats everywhere.. engine itself seems happy enough
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I don't have this exact thing, but I do seem to have an exhaust which makes too much noise - it sounds like a woodpecker when you rev over 3k (definitely a knocking noise rather than rasping) - and the power can be sparadic at times (actually, most of the time) - is there any test I might be able to do on it, save taking the entire exhaust off..
Some daylight might help.
Oh yeah, and there seems to be more smoke than I would like coming from it - although I'm guessing this could relate to my cam covers and the oil thats everywhere.. engine itself seems happy enough
Blue or white smoke?
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appears white
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appears white
Sounds like normal. Will be more condensation out exhaust this time of year. Water is a product of combustion...
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appears white
Sounds like normal. Will be more condensation out exhaust this time of year. Water is a product of combustion...
Well thats something, thanks for clarifying - any thoughts on the british wildlife that sounds like its jammed up there? I guess there is a chance that its engine noise - problem is when its revved that high standing its difficult to identify the source
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We can give it the once over at the weekend....
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We can give it the once over at the weekend....
Nice, cheers guys.
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thanks guys
yes the hissing is coming from the rear of the car i will check the exhaust tomorrow
lee
Yes do it soon, when the one i question went bang, it caused the Mondeo that was follwing to swerve in the road!