I've noticed that my exhaust is becoming increasingly sooty since the last service (45k with cam belt change.) I've always understood that a black exhaust can mean incorrect combustion and could indicate other problems. If this is correct, should I start worrying?

 

It's the 'standard' overfuelling feature!

My exhaust is sooty, and changed the stainless steel to a slightly goldy colour! Nothing a bit of metal polish won't return to standard!

Andy

 

Have you even seen a Scooby that doesn't have a black exhaust?

"They all do that sir!"

Matt.

 

Over how many miles have you been checking?
In just town driving my uk 99my with SSbox will take 2 or 3 weeks to show much carbon, and after a fairly quick 260ml. round trip to the N.E.C. the other week there was only a very light coating.
JohnD

 

a moderate amount of soot , as has been said above, is normal - however if this increases drastically and you are getting poor (worse than say 19 mpg) consumption - then could be a failed O2 sensor - not that critical as running rich is better than running too lean - you can have the lambda sensor checked using the subaru select monitor - it will show how many crosspoints are registered and how quickly the ecu responds to the sensor in a realtime graph - a cruder method would be to check the exhaust gas with a probe - any old garage can do that.

replacement sensor is about £90 + fitting - may pay for itself in saved fuel over time :-)

whereas the saying 'they all do that' has some bearing here, I think it is a question of degree - I would be more worried by a white deposit or water than a build up of soot.

Paul W

 

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by JohnD:
<B>In just town driving my uk 99my with SSbox will take 2 or 3 weeks to show much carbon, and after a fairly quick 260ml. round trip to the N.E.C. the other week there was only a very light coating.
JohnD[/quote]

John, how can you tell how black it's getting (relative to the last time you looked)? Do you clean the carbon off or something?

Matt.

 

Matt
When I clean the car I clean the stainless steel tailpipe with a piece of kitchen roll then lastly wipe the inside. May seem a bit sad but its all part of keeping the whole car clean! (legacy of having a son with a concours Cossie!)
JohnD