Golf Mk4 2.0 Overfuelling

[golfgtimk28vman]

Hi,

I have a Golf Mk4 2.0 petrol and the average MPG has dropped dramatically, going from a steady 32 to a eye watering 19 MPG. Does anybody know what the problem could be?

There's no engine management light that's come on, although a friend with a diagnostics unit did come up with the following codes : P0171 and P0134.

It's going into the garage tomorrow, but can anyone help with advice so that the garage doesn't mug me for a job that doesn't need doing and it still have the problem? Has anyone had this problem and solved it?

Many thanks in advance!

[Kitten]

My 2.0 has just started doing the exact same thing. I haven't managed to get it looked at yet though, might have to wait until Monday :-( I noticed mine dropped to 26mpg on a motorway trip, normally I'd get 36. And only 244 til the petrol light came on. 

[Kitten]

I've been looking around the interweb and chatting with my colleagues and it seems that fuel additive like cataclean or bg44 is worth a try. Also I might stick in some Shell v power, see if that helps clean the system. I might otherwise normally fill up on the cheap stuff at supermarket petrol stations

[Wazzzer]

A quick google search with those numbers

http://www.obd-codes.com/p0134

http://www.obd-codes.com/p0171

Basically you have a dead pre cat lambda sensor

[Kitten]

Got the diagnostics on my car and no surprises lambda sensor showing fault. Had been noted as intermittent last service. I put the bk44 in, I've only done 11 miles and already the average mpg on the trip computer has gone from 26 to 33mpg. Let's see how long a tank lasts...