Luminous

iTrader: (3)

Had some hassle getting through the MOT today with my sports cat in the downpipe. I had driven the car for 10 mins before showing up, and they idled the car for another 15 before hooking up the kit.

The limit I was having issues with was CO, limit for me was 0.200, I was kicking out 1.200 Mechanic and I looked at each other, and the scene was set....this was going to take some time then.....

Mechanic instructed his mate to lift the revs to warm the cat, had the car sitting at 3k rpm for about 10 mins watching the CO count fall when all hell broke loose All of a sudden the engine was spluttering, revs falling to almost stall and then jumping back up, it was stuck in some sort of cycle and unable to rev. Was very worrying for me considering the car had never had ANY running issues at all ever.

Of course this happened mid test and totally fooked the readings that has just appeared as if they may have been sufficiently stable to pass Mechanic took his foot off the gas, and immediately the car settled to its normal nice stable idle, and would rev once again.

Fortunately it did get through the test next run, although the idle test was hard as the lack of heat seemed to make the readings start to shoot up. Just about as fast as the mechanic could get through the test we could see the emissions now climbing back over the allowed limit...it turned red, but finished off as an overall green

Till next year then

Anyone have any ideas on the idling issue? Was it the ECU starting to try and correct a too fast idle thinking nobody would actually hold a car at 3k rpm for so long?

D1CCY

You need to drive the car briskly to get the cat properly warmed up. Fast idle won't put much heat into exhaust but will certainly cause high temperatures under the bonnet which the ECU will see and react to one way or another. I wouldn't go back to a garage that ran my car stationary at 3k for 10 mins, that was plain stupid.

Luminous

iTrader: (3)

Hmmm ok, I never thought that idling a car like that would cause that much of an issue. Next year I will have to drive a bit harder and for longer for showing up. We are a little limited around here in where we can go, need somewhere that can do tapey (sp) brake tests.

DeanF

iTrader: (1)

Dodgey Lambda / O2 Sensor

Dean