Mot'ing the old punto to sell it. 2 problems.

Failed on emmisions, lambda reading only. Too high.

Rear lights being affected by other lights. When all the lights are used at once the sidelights dim abit. Now I wired in a rowbar last year so wasnt sure if its because wiring was shared. Unwired the earth from towbar and still did it.

Am i right in thinking a weak battery may do this aswell?

As for emmissions, they failed it because sound deadening has knackered on back box so slightly louder than should be. Willl that effect the lambda reading at all?

emissions are tested with a probe up the pipe. Even if the O2 is running it rich the cat should burn off the excess so the cat is most likely the cause.But if the cat is weak and O2 is faulty, a new sensor might bring emissions down enough to pass the test.

Rear lights have an earth fault.
The tow bar will be much better with relays so fit them while you sort out the earthing.

If exhaust lambda is high, then either mixture is too lean due to faulty lambda sensor or faulty cat which is insufficiently catalysing the reaction between remaining oxygen and combustables.

Well I have a space cat and sensor I could try so may do that. Head gasket is on its way out, ever so slightly so i presume thats not helping

testing car too cold will give same reading as a naff cat, cats have to be very hot to work

I made sure engine was hot when tested. Been running over half hour before test

bredsticz said:

I made sure engine was hot when tested. Been running over half hour before test

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Running as in Idling
or running as in Been driven like its been stolen

Going for my MOT tommorow - going to wrag it around for a lil while before going into the test center

ziggy

idled 20 min so temp was up then ragged the feck outta her all the way to test station. bwt 15 min away

bredsticz said:

Well I have a space cat and sensor I could try so may do that. Head gasket is on its way out, ever so slightly so i presume thats not helping

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Steam from the leaking HG will be cooling the cat and can produce emissions that wont so easily be burnt off by the cat.

Well, I'll sort the HG out, exhaust and see then. If it still fails I'll put spare cat and lambda I have on.
Been sat in shed so long they probs faulty aswell

Cheers ppl

bredsticz said:

I made sure engine was hot when tested. Been running over half hour before test

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its cat that needs be hot not just engine, try rev at 2.5k for 10 minutes

Driving it will put more hot gas down the pipe.

If doing the head gasket, may was well do the pipe and cat etc at the same time.

Well cat been sat in shed for about a year so not sure if it will have deteriorated a bit