Volkswagen Mark IV Forum banner
1 - 4 of 4 Posts

·
Registered
Joined
·
20 Posts
Discussion Starter · #1 ·
Golf 4 PD115 - I have had poor fuel consumption - about 10% down for over a year; I can never get 50mpg out of a tank however hard I try, used to get this fairly often. When I look at my records this seems to coincide with my last cambelt change. The garage assures me that all is well and that this could not be the cause. I changed the coolant sensor as easy to do. No effect. I have put 4 tanks of double dose of Millers through it - no real effect but smoke test improved at MOT. Passes MOTs.

I have all sorts of other changes - new CAT, new AC compressor and so on, nothing correlates with the change in fuel consumption which seems to have been more like a step than a gradual deterioration apart from the last cambelt change.

My theory is that the timing is slightly wrong (crankshaft shifted?) but I can't get this checked as it's nearly as much work as a cambelt change. It drives really well which is perhaps consistent with increased fuel consumption.

Any thoughts or comments; other ideas of causes?

Phil
 

·
Registered
Joined
·
11 Posts
Cambelt a tooth out is a slim possibility, but check the obvious eg check you can push it easily on a flat (no binding brakes) and check tyre pressures. Finally don't trus the display, tank it, zero the miles, drive it ill empty, tank is and take note of the litres used to refill and miles traveled and work it out.

Cheers Greg.
 

·
Registered
Joined
·
747 Posts
egr cloged up with gunk....

crap in fuel filter....

MAF sensor....

Old air filter....?

these would be my first port of call
 

·
Registered
Joined
·
20 Posts
Discussion Starter · #4 ·
Thanks small_engine adn BigJase.

I use the trip computer for fuel consumption with a reset every time tank is filled. Have checked against fill to fill calculations and get consistent correlation.

Most suggestions I would expect to result in a slow degradation over time whereas I have drawn a graph of my records (10 yrs)and smoothing out the general variations there is a definate drop around the time of the second cambelt change. The MAF sensor was changed many years before and there is no significant fuel consumption change when it was changed.

Tyre pressures have been checked many times in the over a year it has been like this. Brakes have been checked also. Both of these again would most likely result in a gradual deterioration.

General views seem to be that a whole tooth out would be too much for it to be driving well. This is why my theory is that as the camshaft is locked in place that perhaps the crankshaft might have moved slightly during the change and this was not noticed.

I'm looking for confirmation of my theory that the timing might be able to be slightly out after a cambelt change without any faults being logged and driving okay or some other failure that could have just coincidentally have happened about the time of the cambelt change.

Thanks.
 
1 - 4 of 4 Posts
Top