Xantia Diesel Lost Power and Smoking like hell

jeremy · Post by **jeremy** » 02 Feb 2006, 23:52

If the exhaust is blocked you will get a build up of of air and exhaust. This will impede flow round the turbo and stop it working properly. It will also mean that the cylinders won't empty properly meaning that there will be a shortage of oxygen available for combustion - so unburnt fuel will be present in the exhaust.

bman · Post by **bman** » 02 Feb 2006, 23:52

do u need a cat on a diesel for mot seeing as they only do a smoke test

Post by **Peter.N.** » 02 Feb 2006, 23:55

No, I dont think you do. Mine hasn't got one anyway and I have heard of people taking them off.

bman · Post by **bman** » 03 Feb 2006, 00:01

just a thought it was getting slow then towed an unladen car trailer about that was when i realised it was strugggling then when i picked up a megane on it it really struglled but got there just but now its like i've got a sherman tank in the boot, will get mi welder out and make up a de cat pipe i guess

zzf00l · Post by **zzf00l** » 03 Feb 2006, 06:46

Aren't the pipes from a 'non-cat' Xantia interchangeable with a 'cat' version??

jeremy · Post by **jeremy** » 03 Feb 2006, 09:56

Just a couple of things - the rear silencer and other bits of the exhaust may be clogged as well - but probably the catalyst is the first to do.

The second point is that there is a risk that the greasy dirt in the silencer may burn off - resulting in smoke and the posibility that it will continue to do this when its stopped. this had happened to me and I thought at the time the best thing was to keep driving gently - to keep air moving over the exhaust to cool it and prevent excessive heat transfer to the car.

Post by **Peter.N.** » 03 Feb 2006, 10:43

Having exhausted (no pun intended) every other possibility, it seems that the cat is the most likely culpret. Let us know how you got on.

Allanxantia · Post by **Allanxantia** » 03 Feb 2006, 10:53

Just a thought. As it is gradual. Is it a possibility that the valve seats have become pitted, or the camshaft guides have worn and the valve clearances need shimmed. Very easy to check and it would display these syptoms. It happened to me on an old diesel 309.

Post by **Peter.N.** » 03 Feb 2006, 11:03

Its a thought, but I doubt if that would limit it to 3000 rpm, sounds more like an obstruction. Never having had anything with a cat I shall be interested in the outcome.

Kowalski · Post by **Kowalski** » 03 Feb 2006, 13:31

My CAT got partially blocked and when I took it off (replaced it with a non-cat pipe) the fuel economy improved by about 5mpg. The car was never really struggling but low down torque did improve with a new pipe.

bman · Post by **bman** » 06 Feb 2006, 20:58

Problem solved!

cat was buggered but that might have something to do with the embedded exhaust turbine and bush..... although the current turbo is fine, thinking it must of gone bang in a big way on the previous owner and the remains never recovered anyway goes like stink with the straight pipe. magic
thanks to everyone for the suggestions

Post by **Peter.N.** » 07 Feb 2006, 08:51

What were the odds of someone guessing that! Pleased to hear that you've cured it.