Hey folks, got a tale as old as time; failing my MOT on emissions with High Flow Cats.
Taken the Z for it's first MOT under my ownership. The seller informed me the car has High flow cats and a MagnaFlow catback exhaust - I visually confirmed that it wasn't on test pipes. It's passed all of it's prior MOTs on emissions, but this time the test registers a Carbon Monoxide reading of 0.865, 4 times over the legal limit of 0.2.
Took the car out for a spirited drive, high revs, oil temp up at 110°C, and whacked it straight back into the test, but the reading didn't change outside of a margin of error. I don't imagine Catalyst cleaner will drop the result by 4x.
Outside of the test, I've regularly had the car throw a CEL for both O2 sensor banks. A prior owner had extended bungs welded for the lambda sensors to attempt to address this fault. I usually reset it with an OBDII scanner and it vanishes for a week or so.
I'm wondering whether I have the same issue experienced by this gentleman , a lambda offset applied by the ECU, causing a rich map. I'm not sure what equipment I could cheaply purchase to check for this, or whether it'd appear on a standard OBDII scanner? I don't have an EcuTek flash on this car. The car generally smells extremely rich always, not just on cold start.
Outside of this, with the Carbon Monoxide reading not changing when extremely heated (and such a high reading), is it possible the cats are completely blown through? I'm open to replacing them with a new set, but I'd hate to go through the cost and trouble only to fail again. If so, any reasonably priced HFC recommendations? I'm seeing mixed reports on the Berk Technology and Torqen ones.
The garage informed me there is no exhaust leak. I can't confirm when the HFCs were fitted, or the brand, as it wasn't the previous seller who had the work done.
Any help greatly appreciated