Emissions keep failing
 

I thought I'd lob this out to the combined knowledge on here. 2004 1.8 n/a, 160000+ miles. Main fail at MOT was emissions. With Trikeys help, we got it down to dodgy loom on the MAP sensor (changing resistance when moved) so have changed that. Failed even worse on CO, even though T4 said all was OK apart from upstream lambda not functioning. Change lambda, still silly CO % on last test. Plugs are pretty new, air filter clean, been through all the other sensor plugs etc and cleaned/lubed. Would a duff injector cause high readings?

Catalytic converter not doing its job.....

Has the car had a decent run in the last few months? It is amazing how much the figures will come down after 20 or 30 miles on the motorway at the legal limit, do it in 4th just to get the temps in the exhaust up.

The technical term being an Italian Tuning ;)

Do you ever see the yellow engine warning light?
If so, the catalyst is failing.

TC

or drive it like you have stolen it :)

macafee2

Yes exactly :D.

I was struggling with a Rover 45 owned by an old boy recently on its MOT. It was way off on the Emissions so a bottle of injector cleaner and an ''Italian tune up'' had me back for a retest a few hours later. It passed and even the tester was amazed at how low it was compared with the previous readings. My guess the old boy probably hadn't revved it passes 2k in the last year.

I agree with SCP. Put a good engine / cat cleaner in and give it a good revy run. I think Forte is the best, but have used Cataclean when I’ve needed something quickly. Redex is not in the same league for this purpose IMO.

The cat may need replacing. Had this on a previous non mg rover car. Failed on emissions, no engine warning light or anything but the cat needed replacing. Once replaced it passed no problems.

Yes a new Cat will often get them through a test but the quality of non original cats is often quite poor and they will often only last a couple of years max. If you can get the original Cat to pass you it will be a better job and be a lot cheaper.