I know this has probably been posted time after time but I was just wondering whether you could help. I have a vrs Octavia mk1 and the engine management light keeps coming on out of the blue. If I leave it long enough it will go out but my boyfriends has a code reader and it reads system too rich bank 1. With the code reader you can erase the code but obviously this doesn't get rid of the problem. It will go off for a few hundred miles then crop back up. We were just wondering whether you had any opinions on this? He replaced the air flow sensor about a year ago, although this could be at fault again? He replaced the temp sensor for the matter of £6 but this didn't have no effect either. So he was wondering whether it could be the lambda sensor and if so which one. Your thoughts and comments are appreciated. Thank You

Charlie

I think your on the right lines with the lamda sensor, although I not 100%.

Not sure which one either, you need vagcom really which will give you more info.

Cheers for your reply. How many lambda sensors is there?

There are two. I think theres one before and one after the cat.

HTH

Does your code reader give any other information. Usually there will be something like Additive (Add.) or Multiplicative (Mult.) after the code.

Additive means that the fault is ocurring when the engine is idling, Multiplicative means that the fault is occuring when the engine is doing some work.

The first probe feeds back information to the engine control unit on the gasses that leave the engine. From the composition of these gasses it can work out whether the fuel mixture is lean or rich. If the mixture deviates from the ideal, the ECU 'Trims' the fuel. Once the fuel trim exceeds a 10% limit either way it will throw the engine light on.

If it is rich, you can look at it in two ways:

There is too much fuel going into the engine

or

There is not enough air going into the engine

It could possibly be the first probe reporting back to the engine control unit inaccurately, though it could be other things like high fuel pressure, dirty fuel injectors, loss of induction air.

I would try a throttle body clean/reset, inspection of the intake air hoses/intercooler, erasing of the learned values in the engine control unit and some fuel injector cleaner first, as these cost less to do if you have access to something like VAG Com/VCDS.

Hey, thanks for your comments. I said on idle. Could this mean it might be the air flow meter? I was gonna unplug this tomoro and see if it makes a difference. Its very lumpy and flat sometimes, which come to mention could be losing air thru a lose boost pipe or something?? Ill try give that a go, thanks.