Hello,

I drive a 2.0SLX 115hp Octavia /year model 2001, 83,000 km passed, engine APK/. I have the following problem - fuel consumption has increased lately to 18-20 L/100km while driving in town and when at idle fuel meter shows 2.0-2.5 L/h, instead of 1.0-1.1 L/h where it used to be up till last week. One interesting observation I have made - when stopping at traffic lights for examp. and releasing the accelerator and gears to neutral, fuel consumption increases sharply from where it is - say, if it is at 4.0-5.0 L/h it goes sharply up to 8.0, 10.0.....15.00.....even 20.0 sometimes and then sharply drops to 2.0-2.5 L/h where it stays while at idling. And idling is unstable. I`ve noticed also (something like) water coming out of the exhaust pipe, mixed with small carbon, or coal-like particles in it. Also, a bad smell of gas, (not gazoline) all around.

When I went to the nearest Volkswagen Centrum the test showed "Long Term Fuel Trim System too Lean" fault and "O2 Sensor Circ.,-Sensor1 No Activity Detected" fault (Volkwagen codes P1128 and P0134 and also P0171). A thorough check showed O2 sensor, fuel pressure and MAF sensor functioning well. After no cause for these faults was found, errors from the computer were deleted and everything was fine for some 30 km. Then it appeared again - fuel comsumption back up to 2.0-2.5 L/h. at idling, idling unstable and 20L/100km in-town ? Otherwise, I have no problems when accelerating or when at higher speed (except for higher fuel consumption). What could be wrong :( ? Anyone have an idea ?

Can anyone offer and help or advice?

I have a 99 VW Bora 2.0 8v with the same fault, the engine is probably the same, the local mobile tuning bloke told me lamda sensor 1 wasn't switching and advised me to change both sensors.

I have just had a new cat fitted

Perhaps the Cat failure was caused by the Lamda sensor being faulty.

Perhaps the Cat failure was caused by the Lamda sensor being faulty.

It is possible, only found out when it failed MOT.

Passed when retested after cat fitted, then fuel consumption went up and noticed the smell.

So got it checked O2 sensor 1 was faulty, revved engine, then ok.

Fault is intermittent, but now seems to happen a lot.

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