NCT emissions failue - 98 Corolla

TW2401

My Corolla failed the emissions test today with the following figures:

Engine temp 83C

Low idle ( 710 rpm ) CO 10.68% ( above 0.50% fail )
HC 775 ppm ( above 0 ppm fail )

Lambda 0.81 ( should be between 0.97 and 1.03 )
High idle (2,680 rpm ) CO 6.81% ( above 0.30% fail )
HC 425 ppm ( above 200 ppm fail )

So it has failed under all 5 tests. It has 80K miles done.

It passed its previous NCT 6 months ago without any problems.
Will replacing the catalytic convertor fix it or are there other possible causes?
Thanks

Interslice

Looks like there is something wrong with the engine itself. Must be running badly? hesitating/misfiring etc. Needs a decent mechanic to have a look I'd say.

nct tester

There's a vacuum sensor mounted on the bulkhead in the middle with a short flexible pipe that runs to the manifold , sometimes it pops off the sensor or splits as its a bit too short to allow for engine flex. Car never passes emissions if this happens.

selectamatic

Cat is the last thing to replace and don't let a mechanic replace it with a cheap generic job as they are 100% sh1te. As above ensure all sensors are ok then;
First port of call would be air filter, clean throttle body, check plugs and leads, ensure the thermostat is allowing the car to reach operating temps then finally a dash of diptane and a few good long drives if the car doesn't pass after all that I'd be very surprised but if it didn't then it might be time to consider a new cat. A 4efe corolla with sub 100k miles is barely run in so I highly doubt there is any major engine problems.

Mgit

nct tester wrote: »

There's a vacuum sensor mounted on the bulkhead in the middle with a short flexible pipe that runs to the manifold , sometimes it pops off the sensor or splits as its a bit too short to allow for engine flex. Car never passes emissions if this happens.

100% agree with this, I had this exact problem on mine and unfortunately had the catalytic converter replaced by time i found the crack in the little pipe to bulkhead

jca

TW2401 wrote: »

My Corolla failed the emissions test today with the following figures:

Engine temp 83C

Low idle ( 710 rpm ) CO 10.68% ( above 0.50% fail )
HC 775 ppm ( above 0 ppm fail )

Lambda 0.81 ( should be between 0.97 and 1.03 )
High idle (2,680 rpm ) CO 6.81% ( above 0.30% fail )
HC 425 ppm ( above 200 ppm fail )

So it has failed under all 5 tests. It has 80K miles done.

It passed its previous NCT 6 months ago without any problems.
Will replacing the catalytic convertor fix it or are there other possible causes?
Thanks

Those figures are atrocious it must be running terribly and eating juice. Get a decent mechanic to look at it and don't let him just stick on a catalytic converter without finding the root cause. There must be a cylinder dead to give you figures like that.

Stoolbend

Does the car drive alright besides?

Have you had a timing belt fitted since last NCT?

Edit; Just realised this thread is from May.

jca

Stoolbend wrote: »

Does the car drive alright besides?

Have you had a timing belt fitted since last NCT?

Edit; Just realised this thread is from May.

I never spotted the date, most annoying. Unfollow.