MOT / Emissions

[Koren]

Couldn't get through the emissions test. Forgot which test it was but it was the middle one, with a target of below 200ppm. It started reading at 900 but dropped steadily when held at fast idle, but only dipped as low as 250 ish. Engine was warmed up. It has a rebuild engine with street port fitted 6k miles ago. It did have a fault code come up a couple of times for o2 sensor. I've cleared it a couple of times, but it doesn't come back straight away - usually only after a spirited drive. Could it be as simple as the sensor, or is there likely more to it? Does premix affect emissions? Wondering if I should top up the tank to dilute the premix!?

[New Duke]

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[Koren]

100%? Not worth trying the o2 sensor?

[Koren]

This test is very much down to the testers technique.

The PCM is clever enough to realise when the throttle is being held at "high idle", in neutral, and it drops the revs just before the test timer runs out. If the tester sees the revs drop and blips the throttle to catch it, then the emissions spike and it's a fail.

Making sure that the battery is fully charged, everything (heated rear window, seats, fans, a/c, etc) is off, can help.

Or just find a tester with a lighter right foot.

[boosted]

Bottle of cataclean worth a try for £15.00.

I used the stuff on all my car with great success.

Sent from my SM-N950F using Tapatalk

[geofftl1000r]

I run approx. 150ml of 2-stroke to a tank of fuel. Last MOT I forgot to run it down and fill with no 2-stroke oil. She still passed the emissions test.
The car came with a sport CAT but I don't know anything else about it. It does bring up the error code on longish motorway drives if I cruise along.

[Scartlead]

Thankfully don’t have to worry about fast idle for the mot

[geofftl1000r]

The car came with a sport CAT but I don't know anything else about it. It does bring up the error code on longish motorway drives if I cruise along.

That's the only drive mode that the PCM can check if the cat is working - which suggests that it's not really up to the job.

Make sure that the MAF is clean and ignition system is 100%, as any error in fueling will cause the cat to struggle.


Sent from my SM-G800F using Tapatalk

[manuRx8]

This test is very much down to the testers technique.

The PCM is clever enough to realise when the throttle is being held at "high idle", in neutral, and it drops the revs just before the test timer runs out. If the tester sees the revs drop and blips the throttle to catch it, then the emissions spike and it's a fail.

Making sure that the battery is fully charged, everything (heated rear window, seats, fans, a/c, etc) is off, can help.

Or just find a tester with a lighter right foot.

Please, read this:
viewtopic.php?f=104&t=77722&start=50#p1180047
It could be usefull for you