Griffith 4.3 HC Emissions

[voso1]

My 1992 Griff 4.3 has failed NCT on emissions. The report says HC 1255ppm (above 750ppm is a failure).
CO 3.18 vol%. Pass level is 3.50%--so that's OK.
I live in Ireland, the NCT is the equivalent to MOT in UK. Due to the ridiculous road tax here (€1809 // £1604 p/a) I have not used the car since about 2010.
The car is now a 'classic' and road tax is now €56 / £63 p/a so I intend to use the car again.
I have changed all the obvious things and checked everything that I can think of but no improvement.
I am at the moment thinking it could be injectors squirting fuel instead of spraying. The mileage is 47000, fairly low for 30 year old car!
ANY THOUGHTS?
What are other 4.3's achieving on the NCT/MOT?
Any comment greatly received!!

[sixor8]

The limit in the UK is 1200 ppm for a 4.3 Griffith because it doesn't have a catalytic converter. Some vehicles registered before 1992 had them (Jags, Mercs etc) but there weren't compulsory until 1992 (Jan '93 for cars in stock or yet unsold I think).

To get it down to 750 ppm may require a big bottle of redex, new spark plugs and an Italian tune-up but others may know more. Perhaps an idle speed adjustment would help but the standard ECU cannot be adjusted.

[blitzracing]

If it does not have catalysts it may be as simple as getting the CO trim correct- like setting the basic mixture on a carburettor. Its the hex screw on the side of the AFM, and it sets a voltage on the AFM connector that the ECU reads. Just put the ignition on and read the voltage:

connector as follows:

Red/Black Ground

Blue/Red CO trim value.

This is normally in the range 0f 1.4 to 1.8 volts, with an increasing voltage making the mixture richer. You can set it by ear to an extent by letting the car idle when warm and then reducing the voltage to lean the mixture off until the engine note changes and the idle become unstable. The exhaust will stink as well. then increase the voltage so the tick over is smooth again as the mixture gets richer and maybe half a turn more. Otherwise an exhaust gas test is the most accurate option as you adjust..

If the car has catalysts you need to look at the Lambda trim and cycling. RoverGauge is the easiest
option to do this.

[mk1fan]

What has been done to maintain the car during the 12-years or storage?

If the injectors are blocked - not saying they are - then for not a lot more than cleaning you can fit the 'modern' Bosch ones in the updated thread over in the Chimp enclosure.

[scottliv]

I have had my car for 2 years with 2 MOTs done. Latest was 1058ppm and 2.37%. The year before was very similar- 1021ppm and 2.48%. The test before I bought it was a catalyst test that it passed with flying colours???? Before that it was consistently around 900-1000ppm. One of the first tests that I have in my file is 464ppm and 1.16%.

[voso1]

Fantastic response. Many thanks to all.
I will see what I can do with the AFM.
The 750ppm limit seems very strict if the UK allows 1200ppm.
I will play when the weather gets better.

[Unweder]

No reason whatsoever those hydro carbons should not be in the <300 region never mind 700 plus check the ignition system leads etc and fit some new spark plugs like BP6ES or BP6E (better) not the TVR OE suggested recessed electrode style

[keynsham]

Is it usual for TVR's to be so close to the limits? I have had a lot of old cars when they are set up properly they never got close to the max allowables. Indeed my 1987 VW camper van wouldn't run if the emmisions were at the max limits as it isso rich it won't even tick over!

[QBee]

They are generally set up a bit rich, hence Blitz Racing's comments about leaning the mixture off at least for the test

[Unweder]

A slightly rich CO Dont explain that horrible HC reading though winding/correcting that CO down to 1.5 to 2% is not going to correct that it may nudge it down a tad however

[Classic Chim]

Chimaera 450
Two tests.
L/H is using MBE ignition and 6 grade plugs.

PRE CATS REMOVED on both.

Edited by Classic Chim on Friday 20th January 15:41