Emissions Issues- Help

Not holding to the correct rpm during the test - my first thought's are a partial loss of vacuum or a worn stepper motor. As Cobber says that fault extremely unlikely to be caused by the ECU itself. Robust things these ECUs

There are untold millions of ECU’s being driven around in every part of the world doing, without question, what they were designed to do.
From the moment of their first boot until they are decommissioned (in whatever route that might take) these obediently perform with unerring accuracy their tasks & although there are glitches in systems these tend to be external influences; moisture tops the list.
“Experts” who blame problems on ECU’s are more interested in your money than the health of your car.
Whatever new witchcraft motor manufacturer institute in their new cars, will be the major contributory factors to your motors ill health until the next brainwave is foisted on to us, irrespective of the true problem.
Or am I just getting disillusioned with this motoring caper & the folk who profit from it all.
M

Airportable,
IMHO no you’re not getting disillusioned with the motoring caper. Very wise attitude.

Interesting thread this as my TF has just failed its MOT on emissions. Have post cat sensor replaced very recently. Cat and pre sensor ordered from ‘Bitz. Cat fitted today and the testers said they’d had issues with their test gear but ‘got it sorted’ and it’s failed again. Pre sensor to be fitted. See what tomorrow brings…..
Michael.

That’s interesting their having had problems with their equipment. My chum who does my MOT tests & who had done since the abolition of the man with the red flag, Dave’s kit does a self test against an internal standard & will not allow a test to proceed if there is deviation of more than a few points.
I’m sure most of us, or at least those who brave the test by close observation will be conscious of time gaps in between tests.
I believe these periods are part of the self test & resetting to datum in preparation for the next disappointment.
M

As Talkingcars mentioned, the Pre cat lambda is the critical one for setting the fueling and CO, the post cat one is just to check the result.
Therefore if the CO is outside acceptable readings it should be the pre cat lambda that is changed. As I see it the worst harm a failed post cat sensor could cause would be to bring up the MIL light