1995 1.8i fails emission test at high idle

Hello,

My 1995 1.8i Golf Mk3 (Eng ADZ), is failing its emissions at high idle.

The printout result was as follows:

Eng oil temp during test 69C ( low, I know, as the car was waiting some time for the test and I don't think that they even let it warm up properly)

Low Idle (880rpm)
CO 0.14 vol %
HC 30.00ppm

High Idle (2920rpm)
Lambda 1.01
CO 0.38 vol% FAIL( due above 0.3% limit)
HC 18.00ppm

The cat. was replaced last year, so hopefully it is not a repeat defect, as it was very expensive. I have just replaced the coolant temp sensor and the air filter. I have spoken to a local mechanic and he has suggested putting a fuel injector cleaner into the fuel tank and giving it a "good thrash" before I put it in again for a retest of the emissions.

Does anybody have experience of a similar problem at high idle and if so did a fuel treatment cure it ??? If it did what injector cleaner did you use ?

Thanks,

S.

check the monojet base gasket for splitting
also check that the throttle goes to the return posistion at idle

Thanks for your reply. I will have a look today.
Thanks.

Hello All,

Well I have just checked the gasket and it was perfect and the throttle returned to idle properly as well. So I am still open to suggestions ladies and gents.

I also checked the condition of the throttle body and it was very clean inside.

The oil, oil filter and plugs are due to be changed soon. Could old oil be the cause of the CO emissions being too high at high idle ???

The retest is booked for next Thursday so I have a little time to play with, work permitting.

Thanks again for your earlier suggestion TowcesterVAG.

S.

Passed !

Thank-you all who replied to my thread.

My plan (see above ) worked.

S.