How do

Having a few issues with my rex, had a de-cat on there, popped the cat bk on for the MOT, all done no prob, put the de-cat back on, 20 miles down the road and it's started running rough struggling to accelerate, poor throttle response and its thrown an engine fault light, had the light checked out and it's come up as 'mixture to rich', I tried a compete ecu re-set (20 brake pedal presses), took it for a 10 mile drive and it's doing exactly the same again with the same fault code being thrown up. It this the ECU still learning the parameters for the de-cat or is something else going on here???

Thanks
Scott

 

That sounds like the MAF, kinda like what happened when I accidentally left the MAF disconnected.


Re-learning fuel trims will make for a rough idle, but no more. Worst case it will run off the O2 until it has the trim data it needs. It's possibly your O2 is bad, possible an e-shaft sensor problem, possible you have ignition failure.

 

Maf was cleaned not that long ago, when you say o2, this is the second lambda sensor yeah? ignition is on new sparks coils and magnecore leads

 

2nd O2 (rear) does nothing for the car except determine emissions compliance. Front O2 is the one that is used by the engine to adjust the fuel delivery.