NCT fail on emissions

SCOOP 64

My 1998 Opel Astra fail the NCT only on one thing, was serviced before nct, ,oil, spark plugs,air filter, did take it for a hard spin before test.

Lambda 1.05 not between 0.97 and 1.03 fail/refusal
CO 0.11 vol% above 0.30% Pass
Hc 55ppm above 200ppm pass

Now he actually wrote on the nct document,

" co + lambda fluctuating, never staying still"

but CO looks like a pass?, any idea what could be cause of lambda fail and what to do next to get a pass, Thanks.

Atlantic Dawn

I'd try some Dipetane and a good hard run before getting there, it's only marginally over, should be achievable with the Dipetane and nothing more.

SCOOP 64

Atlantic Dawn wrote: »

I'd try some Dipetane and a good hard run before getting there, it's only marginally over, should be achievable with the Dipetane and nothing more.

just been looking up about high lambda reading with normal CO and HC readings, the most common cause is air leaks, A small exhaust air leak, only a small volume of clean air in the exhaust will cause a car to fail the nct test apparently, not sure if dipetane will will solve it if hole in exhaust but might be worth a try.

JP 1800

The car is running lean, so you either have an exhaust leak or an air leak into the inlet manifold. Diptane will do nothing for this so I suggest having a thorough look over the exhaust and holding a bunched rag into the back of the tail pipe and listen for leaks while the car is running, be careful as to not burn yourself. Manifold leaks can be checked by spraying egr or carb cleaner lightly around the inlet manifold and listen for a change in idle speed which would indicate leaks.

SCOOP 64

Found 2 holes in exhaust repaired with exhaust putty,
Passed NCT with 1.02 Lambda, cheap fix thank christ.