NCT failed - high low idle emissions

mel.b

I have a 99 Mazda 323 which has done 113,500km. Had the NCT done recently and it failed on the low idle emissions.

The details are:

Engine/Oil Temp = 94C
Low idle (720rpm) CO 0.72 vol% (fail is above 0.50%)
HC 152ppm (fail is above 0ppm)

High idle (2940rpm) Lambda: 1.00 - pass
CO: 0.13 vol% - Pass (fail is above 0.30%
HC: 78ppm - Pass (fail is above 200)

Now my car is well overdue for a service, however I have read on here that it may be worth trying some 'diptane' first. With those readings do people think it is worth trying some diptane, or do I really need to get the service done before I take it back for the retest?

Thanks,
Mel.b

gyppo

do the service first

mel.b

Is that because you don't think the diptane will be enough to fix the emissions.

My car was due for a service 6000km ago:eek: have just been putting it off and off and off...

-Chris-

Do the service because the car needs it and your oil isn't designed to last indefinitely.

Get them to check the emissions after the service and see if it's made any difference, or to try and find the issue if it doesn't.

L-M

Do the service, then throw in the Diptane, then give it a good "spirited" drive before you go back in. Go out a stretch of motorway in third gears with the Diptane in the tank.

mel.b

Thanks all. Car is booked in for a service tomorrow.

mel.b

mel.b wrote: »

I have a 99 Mazda 323 which has done 113,500km. Had the NCT done recently and it failed on the low idle emissions.

The details are:

Engine/Oil Temp = 94C
Low idle (720rpm) CO 0.72 vol% (fail is above 0.50%)

Just to follow up, i got the car serviced yesterday and took it on for the retest today. I took the car for a 50min spin on the motorway immediatley before the test, but didn't get around to adding any diptane.

Good news is the car passed:)
Engine/oil temp:59c
Low idle (690rpm). CO 0.44 vol% (fail is above 0.50%)

I'm interested though if someone can explain the enbine temps to me. The first time i took it in and the temp was 94c and i drove the car less than 2km and it was also first thing in the morning. This time i drove the car for about 70km along a motorway at 110km/hr and the temp was 59c

Thanks,
Mel.b

L-M

mel.b wrote: »

Just to follow up, i got the car serviced yesterday and took it on for the retest today. I took the car for a 50min spin on the motorway immediatley before the test, but didn't get around to adding any diptane.

Good news is the car passed:)
Engine/oil temp:59c
Low idle (690rpm). CO 0.44 vol% (fail is above 0.50%)

I'm interested though if someone can explain the enbine temps to me. The first time i took it in and the temp was 94c and i drove the car less than 2km and it was also first thing in the morning. This time i drove the car for about 70km along a motorway at 110km/hr and the temp was 59c

Thanks,
Mel.b

Asking that is like someone giving you €45 euro chnage back out of a €50, you just smile and keep walking

CiniO

mel.b wrote: »

Just to follow up, i got the car serviced yesterday and took it on for the retest today. I took the car for a 50min spin on the motorway immediatley before the test, but didn't get around to adding any diptane.

Good news is the car passed:)
Engine/oil temp:59c
Low idle (690rpm). CO 0.44 vol% (fail is above 0.50%)

I'm interested though if someone can explain the enbine temps to me. The first time i took it in and the temp was 94c and i drove the car less than 2km and it was also first thing in the morning. This time i drove the car for about 70km along a motorway at 110km/hr and the temp was 59c

Thanks,
Mel.b

Maybe your car was waiting longer after you parked it in front of test centre before they actually tested it.

Or maybe your thermostat is gone, and your engine runs at too low temp especially at higher speeds.

slimjimmc

For a start 94C seems very high, the second reading seems more reasonable. Perhaps the engine was running hotter because of the lack of servicing.