Club 80-90 Forums

Fast Idle

CO - 7.114 & 6.832 Should be max .3


HC 784 & 1214 Should be Max 200

Lambda .868 should be between .97 and 1.03

Natural idle

CO 4.091 Max should be .5




Basically my van is burning lots more fuel than it should be. The emissions have never been an issue before. What do i start with?

CU engine, standard carbs, new air filter, sooty plugs.

Got one of those colour tune plug jobs and the flame was orange on tick over, I screwed the smaller of the 2 tick over adjustment screw down until it went blue, it was way out (about 5 turns) so i assumed that was the problem until it failed the retest.

OK, the more i read the more i think he's testing with the wrong limits!

Has anyone got a link to some definitive answers?

E D I T

http://www.motuk.co.uk/images/7.3page6.pdf" onclick="window.open(this.href);return false;

4.5% CO

1200ppm HC

He's got it wrong!

Exhaust Emissions - Spark Ignition - non CAT Test Spark Ignition - Non CAT Test Flowchart
Information Method of Inspection Reason for rejection
When to do the test
It Is recommended that the engine is tested as soon as possible after driving on the road
.

B. Vehicles first used on or after 1 August 1975

1. Check that the analyser probe can be inserted into the tailpipe.

2. Use a suitable exhaust gas analyser to
determine the proportions of carbon monoxide {CO) and hydrocarbons (HC in the exhaust gas over a period of at least 5 seconds at idle.

Note: Any residual hydrocarbons (ie those indicated by the analyser when it is sampling only clean airj should be deducted from the HC reading obtained from the vehicle.

Note: If a vehicle meets the CO requirement at its normal idling speed but fails the HC check, re-check the HC level at a high idle speed of 2000rpm. If the HC reading is 1200 ppm or less, the vehicle will meet both the CO and HC requirements.
. the CO requirement must be met with the engine running at its normal (low) idling speed
. do not use a cold start/cold running mechanism to achieve a high idle speed. Instead, apply light pressure to the throttle pedal.
. HC not applicable to Compressed Natural Gas (CNG) fuelled vehicles.
B. Vehicles first used on or after 1 August 1975

1. The emissions cannot be measured because a tailpipe accessory is fitted which prevents Insertion of the analyser
probe

2. The exhaust gas contains
a. a carbon monoxide content
exceeding the limit for a continuous period of 5 seconds

b. a hydrocarbon content exceeding the limit for a continuous period of 5 seconds.

Ya I think your right....he has got it wrong, will have a good read up in morning at work BUT saying that there is still something wrong with it. HC's are to high and I would be looking for the usual/common problem...air leaks. Vac pipes, balance pipes, so many places to leak..
IAN

Thats at fast tick over..

HC 784 & 1214

I'd guess I'd scape a pass

At that age think its just checked at tickover, but will read up in morning mate...Can't remember

Thanks

If it still has high HC, change the engine oil before the retest or a least disconect the engine breather pipe. Often it is caused by petrol contamination in the oil.

How often is it used? i'd clean the plugs, check timing, change oil and filter if its dark coloured drop some redex in, take it for a good run on way to test centre and if you can get it put straight on emissions test, never fails unless something is wrong.

was wondering if a fill of high octain fuel a few days before mot would bring down emmisions any boffins out there have any answers

Thanks all!

I'll do the oil and clean the plugs.

Timing is fine.

Van used nearly every weekend (winter camping rocks! ).

fullsunian wrote:At that age think its just checked at tickover, but will read up in morning mate...Can't remember

As I said yesterday, at that age the gas test is just at tick over max CO 4.5%, max HC 1200ppm..
IAN

Hi Chris....as Ian has already said, your MOT tester has been using the wrong test data so you are never going to pass with a pre-cat air cooled CU.
The test is at idle with engine oil temp of 80C plus, CO of 4.5% max. Don't worry too much about your 7.1% , your mixture just needs a 1/4 to 1/2 turn in to take it down under the limit. CO tweaks can normally be done by ear....slowly turning the CO screw in until you begin to hear a random miss, then an eigth of a turn out from this point (you are only adjusting the idle mixture as once off idle the carb/carbs use a different jet)
Thats why talk of damageing engines because of a weak idle mixture don't make sense.

Martin

The_blue wrote: CU engine, standard carbs,

It's not a WBX Martin.

Quick update..

Got hold of a gas tester, adjusted the tickover and running mix. Not sure how good the tester is (old thing with a dial) but it was well into the red/rich at first and is now just into the top half of Green/OK.

If only the MOT test had just green and red

The_blue wrote:Quick update..

Got hold of a gas tester, adjusted the tickover and running mix. Not sure how good the tester is (old thing with a dial) but it was well into the red/rich at first and is now just into the top half of Green/OK.

If only the MOT test had just green and red

just tell him he's tested it wrong. he should lift it away from idle or it'll never pass.