My 2003 TDi110 Elegance Estate seems to have suffered a slight loss of performance. By that I mean it doesn't seem to go as well as it used to. It could be my imagination because it's not bad, but I just get the feeling it's not quite as good as it was. I changed the water pump and cambelt about 8 weeks ago. I've double-checked the valve timing to make sure it's right and it is spot on. Same for the pump timing which sits halfway between the centre line and the green advanced line on VCDS. Also my fuel economy has deteriorated too. I used to get 45mpg as an overall average and now I'm down to 40mpg. On a longer run I could get 56mpg if I drove steadily, and today I drove 85 miles for 51mpg. My wife uses the car more than me and she has been doing more short runs lately. This of course will affect the average miles per gallon, but I have a sneaky feeling it's more than just this. The car has done 172,000 miles, but has run very well in the three years I've owned it.

I'm thinking along the lines of carbon/oil build up in the intake manifold. Has anyone ever bothered to remove it and clean it, and if so what is the best way to go about it, what did you use to clean it and how much of an improvement (if any) was there afterwards?

Any advice would be appreciated.

Might be worth checking to see if the EGR assembly is blocked up.

Taking the inlet manifold off is pretty straight forwardf, you might want a new gasket for re-assembly though.

Remove the flexi-90 deg air pipe, undo the 3 allen bolts the EGR assembly (probably have to undo the exhaust pipe feed), and then there are a number of bolts (or allen bolts) to undo for the inlet manifold.

If your wife drives gently, then maybe the turbo is a little seized up..... Does it pull well?

Edited 20 February, 201115 yr by mbames

Might be worth checking to see if the EGR assembly is blocked up.

Taking the inlet manifold is off, you might want a new gasket for assembly though.

Remove the flexi-90 deg air pipe, undo the 3 allen bolts the EGR assembly (probably have to undo the exhaust pipe feed), and then there are a number of bolts (or allen bolts) to undo for the inlet manifold.

If your wife drives gently, then maybe the turbo is a little seized up..... Does it pull well?

Thanks mbames.

It looks like there's something missing from your second sentence, so I can't quite be sure what you mean.

Although my wife drives it more than I do she certainly does not drive gently. In fact she is quite lead-footed. I do tend to get better mpg than she does to be quite honest. She drives it 7 miles each way every day. Her journey includes a four mile stretch of dual carriageway with a hill at either end. She does tend to boot it up the hill a bit. She's been doing this journey since well before we had this car and so nothing in her driving style has changed other than she also does more short runs now. It does pull just about as well as I would expect it to, and someone other than me would probably not even notice the small drop in performance that I think it's suffering. But over 30 years of experience in the motor repair trade is telling me it's not quite right. Having said that I've also been in the situation many times that you can spend time and money on these kind of things and at the end of it no noticable improvement has been made.

My main question is does cleaning the manifold make much of a difference to the performance? And assuming mine has never been done before (and I certainly have never done it on this car or any other) would cleaning it realistically be likely to be worthwhile or a waste of time and effort?

Corrected my sentence.

Cleaning it won't do any harm..... I have various pictures of mine:

http://www.matthewames.co.uk/briskoda/index.php?loc=./20070409_egr

http://www.matthewames.co.uk/briskoda/index.php?loc=./20100314_egr_cleaning