Emission light on + jumpy under slow acceleration

[BMcN]

Car used to have a decat and I replaced it with a standard CAT, after a few miles the emission light came back on.

Secondly, I used RSTuner and loaded on the remap, ever since then when accelerating slowly or even trying to hold a steady 30 in 4th or similar - the car is very jumpy and doesn't feel right.

All plugs and leads were changed not long ago. I would guess the emission light is the O2 sensor after the CAT? Would this also cause the second issue or is it likely RSTuner related?

Thanks.

 

[BMcN]

Anyone?

 

[one in a million]

try a new coil pack, my car is in a similar situation as yours

 

[pinky]

One of my o2 sensors caused basically the same symptoms ...think it was the one before the cat though. cant you get on a diagnostic machine?

 

[Lagerlout]

RS Tuner should tell you if your lambda is ok. You should see, after it's been idling for a minute or so, the fuel mixture going from lean to rich in a repetitive cycle.

EDIT - Light blue line on this plot. Should go no higher than 1v and no lower than about 200mV iirc, with a differential of 500mV. Info gleaned from tinternet/Henk when having a few issues with mine.

 

[Jonny1*2]

It might be the pre cat lambda. Secondary does nothing.

 

[BMcN]

Sorry to dig this one back up but the light came back on and I have an MOT this week. I have done 2 screenshots, one plotting the live data as Lagerlout said.

The front o2 sensor is jumping between 9mv and 19mv, so I guess its needing replaced. (Light blue line)

Is this the correct one? http://www.eurocarparts.com/ecp/c/R...095db08b275572865f651f41b84757f154161040&LAMS

Anywhere else cheaper?

Lastly - will it pass the MOT or will it fail on emissions?