UK-POLOS.NET - THE VW Polo Forum

I have a 2012 1.2htp.

When i bought it it had a check engine light and i scanned the code it had a code for the bank 1 lambda sensor. I also noticed that it had a non genuine catalytic converter in it. I then failed on emissions (see the readings beside the pink highlighter)

After i failed emissions i scanned codes again and catalytic converter inefficiency came up.

I then bought a genuine second hand catalytic converter and bank 1 O2 sensor, i ran this for about 150 miles and the codes never came back.

So I then put it through another NCT (MOT)

As you can see from the picture with no highlighter, the Lambda has now got even worse, the CO has increased, and the HC has improved slightly.

Where do I go from here. I obviously have some sort of rich fueling problem but with no fault codes I'm not really sure where to look?!

Any help would be greatly appreciated.

Hi there. I'm guessing you've resolved this now. Anyway, for other users here, I've just had a similar problem with my son's car. It was a complicated fix because the new MAP sensor I brought was the wrong one. It fitted fine and original Bosch but I didn't check the part number codes on the device. It sent the car ECU the wrong signal and very rich mixture. I cleaned the old one and put it back in. I'd checked a lot of the wiring as fault codes suggested signal was grounded. I also took out and cleaned the fuel injectors using an ultrasonic bath. I took out and cleaned the first lambda sensor. It's running better and OBD reader shows MAP sensor varying with revs. Also lambda integrator isn't sending massive negatives signal show it's not getting rich fuel mixture any more. I cleaned the throttle body too as it was a bit coked up but I think that's been fine all along. I'll take it for MOT retest and see. I'll update either way.

Do a compression test first, these engines suffer with burnt out valves.