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Cassyp said:

Hi my micra won't pass an emissions mot test,last year it scrapped by as they fitted a new Cat,it's had 2 new lambda sensors and now the test is reading
fast idle co 9.96,he 9.96,lambda 0.734
The garage don't have a clue what to do next. A neighbour who's been a mechanic for 35yrs reckons I dont drive hard or long enough as tge car never get hot. Mot retest tomorrow after I've been driving it at 4-5 rev's over the last few day's. Anybody got any idea's please.

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Micra Paul said:

Refill it with E5 Shell V Power or BP Supreme/ Super unleaded 98/99 Ron & drive it up to 10 miles approx. at high RPM; easy with fourth/ third gear use.

Cheap super market fuel E10 & lacks optimum fuel chemical detergents to clean the combustion by-products.

Repeated short journeys never get the engine & rear exhaust silencer box hot enough to boil off the combustion exhaust condensate by-products water that builds up in the exhaust system.

Some people also recommend injector cleaner but this is not necessary with good quality fuel.

Book the MOT for a specific date & time & drive it 5 miles at high RPM to get it well hot before delivering it for the MOT test & wait while its done.

A service new air filter & plugs can help,

Google search; HJ.Co.UK Shell E5 Supreme unleaded.

Shell Super unleaded - Page 2 — MoneySavingExpert Forum

HJ.Co.UK Shell Supreme unleaded at DuckDuckGo

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Cassyp said:

Hi thank you, I have been taking it out over the last 2 days doing exactly that. M O T is today at 2.15 so going to drive it for an hour before and fingers crossed. I love my car and she passes on everything else,so she's a good car. Thanks again for your advice.

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Cassyp said:

She failed again,the emissions where lower but the CO reading was going up and down and not settling on a number this time..
The garage says it needs new back lambda sensor, but it changed 2yrs ago and the front one 3wks ago..really don't know what to do.

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