Many thanks to HJ and all you others for the advice regarding the failed Lambda reading on our 1994 Micra (59k miles) posted 12/05/01 15:44.
Last night I added 15ml of injector cleaner to about 15 litres of ULSP in the tank and drove at speeds of up to 60mph in third and a good 70mph in fourth for about 5 miles on the motorway. I repeated the driving procedure to my local Nissan main dealer for an MOT this morning (a distance of 6 miles). It passed the MOT test with flying colours.
I am still very suspicious of the results from the other while-you-wait; free re-test concern. They (doom and gloomily) diagnosed the exhaust gas sensor as not working at all, and were proposing replacing the sensor at a cost including labour in exess of £100. They did the fast-idle test twice, but I would estimate at rpm far in excess of the test specifications (although their rpm printout appeared correct). I suppose the unsuspecting would be prepared to part with this sort of money in exchange for the coveted certificate.
So a warning to all. Some testing stations are out to generate work (and profits) for their workshops, some of which may be unnecessary. You may end up paying for things which are not even done.
Thanks again to you HJ and other knowledgable contributors for the feedback.
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I solve the problem of the MOT centre trying to generate work by only doing the MOT there. I always get the necessary repairs done elsewhere and bring it back for retest. If they know they will not get any repair work they just want to get the MOT done as quickly as possible!
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Doing the fast idle test at very high RPM is a way of getting the car a PASS certificate. Your MOT tester was trying to help you, not the other way around.
At leat that is my experience from a tester who actually tries to help. He always manages to pass my car.
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Yes, Richard is quite right - this tester was actually trying to help you. By doing the test at higher revs the catalyst will work hotter and more efficiently - burning off the accumulated rubbish that hampers efficient catalyst operation.
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My MOT tester always HELPS me by letting me PULLLLLLLL up the handbrake, STAMPPPPPPP on the brakes and rev the MERRYYYYYY HELLLLL out of the mota.
A helpful MOT tester is like an angel in the kitchen and a w**re in the bedroom - worth keeping.
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