Emissions fail - exhaust leaks?

miscuser

Hi
My car (99colt) failed on emissions and has a couple of exhaust leaks

Is it possible the exhaust leaks could cause the high CO( 7.24% high idle) and HC( 1546ppm high idle) or will it definitely need more work

Thanks

JP 1800

definitely not caused by exhaust leaks. The car is running very rich, one or more of the engine management sensors is most likely faulty.

miscuser

that's what i thought

is that the 02 sensors?

JP 1800

It could be O2 sensor, MAP/MAF, Coolant sensor, spark plugs HT leads ect. The car needs to be diagnosed properly to determine the exact cause so ideally bring it to a garage and get the codes read.

CarFan100

OP here (new account)

repaired exhaust and fitted new plugs
mechanic said the old plugs were fine as they were changed for last test but changed them anyhow

the emissions this time were miniscule

ENGINE TEMP 94 DEGREES
CO 0.01
HC 18PPM

damon5

Hi wondering what your engine temp was when you had the previous test done as I see you had a good high temp which is supposed to be good when testing for lower emissions, as the NCT website says the test should be done at normal operating engine temp,Also regarding the exhaust I had a middle box exhaust fitted a couple of weeks before my nct that was a cut and welded job and a 300 mile long drive with dipatene added and my emissions jumped up drasticly for some reason,since getting exhaust done sounds like its blowing,wondering is there any connection,thanks......

jimgoose

JP 1800 wrote: »

definitely not caused by exhaust leaks. The car is running very rich, one or more of the engine management sensors is most likely faulty.

Depends on where in the exhaust the leak is. A hole in one or more headers could easily send the mixture haywire rich.

CarFan100

damon5 wrote: »

Hi wondering what your engine temp was when you had the previous test done as I see you had a good high temp which is supposed to be good when testing for lower emissions, as the NCT website says the test should be done at normal operating engine temp,Also regarding the exhaust I had a middle box exhaust fitted a couple of weeks before my nct that was a cut and welded job and a 300 mile long drive with dipatene added and my emissions jumped up drasticly for some reason,since getting exhaust done sounds like its blowing,wondering is there any connection,thanks......

81 last time
I put in 10L litres of alcalyte petrol for test this time, I heard people are getting low readings with this method

Have you failed NCT?

damon5

CarFan100 wrote: »

81 last time
I put in 10L litres of alcalyte petrol for test this time, I heard people are getting low readings with this method

Have you failed NCT?

No passed just by the skin of my teeth,my engine temp was 22 degrees when they tested it because of their backlog with cars sitting outside for 30 to 40 mins.That goes against there normal operating engine temp for testing which they state in their regs....

damon5

alcalyte petrol....never heard of this,can you enlighten,thanks..

CarFan100

damon5 wrote: »

No passed just by the skin of my teeth,my engine temp was 22 degrees when they tested it because of their backlog with cars sitting outside for 30 to 40 mins.That goes against there normal operating engine temp for testing which they state in their regs....

That's crazy
I have heard of one person staying in the car keeping it running
While another person goes in with a second set of keys

allthedoyles

Where do you buy this alcalyte petrol ?

CarFan100

allthedoyles wrote: »

Where do you buy this alcalyte petrol ?

It's for lawnmowers and the like, garden stores

As far as I can tell from the spec it reduces Co and HC emissions by 25% or thereabouts

The spec claims lots of other benefits not relevant to NCT emissions testing

damon5

CarFan100 wrote: »

It's for lawnmowers and the like, garden stores

As far as I can tell from the spec it reduces Co and HC emissions by 25% or thereabouts

The spec claims lots of other reductions not relevant to NCT emissions testing

If it would have failed I would have appealed the test being done on an engine
not at normal operating temp,maybe if it failed they would have tested it at proper operating temp and hopefuly then passed.Thing is it should not have been tested at 22 degrees,its all a farse...

barneygumble99

If the car passes at 22 degrees why would they need to take a temperature?? It's only diesel cars that have to up to normal operating temperature (80) before the test can commence.

damon5

barneygumble99 wrote: »

If the car passes at 22 degrees why would they need to take a temperature?? It's only diesel cars that have to up to normal operating temperature (80) before the test can commence.

EXHAUST CO/HC/LAMBDA (This item does not apply to vehicles first registered before 1st January 1980)
Method of Testing
1. Check visually in the case of 4 stroke spark ignition engines (petrol or gas) that the emission control system is complete and properly connected and that there are no leaks in the exhaust system.
Pre Jan 1994 Registrations
2. With the engine at normal operating temperature connect the CO/HC meter as per manufacturer’s instructions. Raise the engine speed to approximately 2,500 rpm and hold for 20 seconds. Allow the engine to return to idle and the emissions readings to stabilise. Note the carbon monoxide and hydrocarbon content of the exhaust gases at normal idle speed.
Post Jan 1994 Registrations
3. For vehicles first registered on or after the 1st January 1994 raise the engine speed to 2,500 rpm or to a speed specified by the vehicle manufacturer and hold for a minimum of 30 seconds. Check the HC, CO and Lambda values. If the exhaust emissions are not within the specified limits with the vehicle engine at """ normal operating temperature """ raise the engine speed to 2,500 rpm or to a speed specified by the vehicle manufacturer and hold for 3 minutes and note HC, CO and Lambda values. Allow the vehicle engine to return to normal idle speed and the exhaust reading to stabilise and note the CO reading.


From the NCT PDF file...