NCT High Idle advice

STi Type R

Sunday Drivers
Looking for a bit of advice.

97 JDM STi.

Passed NCT last year. CO High Idle failed this year. Same CAT, ECU etc. I always remove sports exhaust, box etc. and replace with standard system. Put back in standard ECU. Took it for a good spin beforehand.

HIGH IDLE THIS YEAR
Lambda: 0.99 - PASS
CO 0.34% - FAIL (above .30% is fail)
HC 85ppm - PASS


HIGH IDLE LAST YEAR
Lambda: 1.01 - PASS
CO 0.01% - PASS (above .30% is fail)
HC 32ppm - PASS

Hadn't been driven in around 3 months, so not sure if that's relevant. Petrol gone off? (if that's possible).

Should the CAT warning light (see attached photo) come on before the car starts? It comes on with all the warning lights when I turn the key and stays on until I start the car. It goes off with all the other warning lights. No CEL light and not coming on while driving. I actually cannot remember:(

Thanks.
 

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Mine was the same I put the bung in and it passed
Something to do with air getting sucked back in
Lad in the not held a lump of cardboard over it and it got better but still failed ....but bung passed
 
That's only a cat temp light so should always go off with the rest and as Keith said try a bung in it but maybe get it checked before hand to make sure it's spot on as to not have it fail again
 
The problem with mine was the probe the not used wouldn't go up far enough so was picking up false reading because air was getting sucked back in the tip.
Stick up a pic of the back box and see if anyone has a lend of a bung or only cheap on fleebay
 
It's 3" dia STi.

Pic attached.

Anubody have a link or pic of what they used?
 

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How long are you putting the cat back on before test? Put some dipetane in and get it nice and hot. Give it a couple hard drives the few days leading up to NCT to get the precious metals working. Then a good hot drive on the way to the centre.
 
Living in Kerry.

CAT and standard system only went back in the day before NCT.

Done about 100km in total the day before and just before NCT.

Based on the lambda reading is it safe to assume the front oxygen sensor is working ok?

Thanks.
 
How long are you putting the cat back on before test? Put some dipetane in and get it nice and hot. Give it a couple hard drives the few days leading up to NCT to get the precious metals working. Then a good hot drive on the way to the centre.
Do not drive a Subaru hard/on boost with Dipatane in the fuel mix.

Sent from my SM-N910F using Tapatalk
 
Dipetane did the job for me when failed but i didnt went red lining it, left the car runing pre test she was nice and hot and passed
 
Car passed retest tonight.

High idle CO 0.03%.

Dipetane added. New gasket between turbo and downpipe also.

Sound fella in the centre as well. Asking about the car.

Thanks for the advice.
 
12 months later - same craic only worse!

97 JDM STi.

Passed NCT last year after re-test. Same CAT, ECU etc. I always remove sports exhaust, box etc. and replace with standard system. Put back in standard ECU. Took it for a good spin beforehand. Dipetane added.

HIGH IDLE THIS YEAR
Lambda: 0.90 - FAIL (outside 0.97 AND 1.03 is fail)
CO 3.70% - FAIL (above .30% is fail)
HC 133ppm - PASS

For ref:
LOW IDLE THIS YEAR
CO 0.04% - PASS (above .50% is fail)
HC 88ppm - N/A

Any thoughts?
 
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