theelanman wrote:Ive never done it but I belive it goes like this....
make sure the car is warm before you start
turn ingnition on...
put into service mode
start the car
run the engine whilst you put the gas analyser in the tail
wait for the analyser to register...note the reading
tweek the blue screw in one direction....
recheck the analyser to see if the numbers have gone up or down...
twiddle away until you get to about 2%~2.5%.....
turn the ignition to slot 1
take out of service mode
turn off
or at least that the way Ive thought it was done.....
cheers
G
Very nearly correct!
But to put it into service mode you start the car first, then put in the paperclip (otherwise it is in diagnostic mode).
I did a write-up on the procedure a couple of months ago (but cant find it now

).
To locate the CO pot:-
open the glovebox, swing it all the way down by easing the catch past the lip on the dashboard, so it swings right down. If you haven't already emptied the glovebox, it will do it for you at this point

.
Locate the ECU (metal box, approx 7" x 4" x 2" with a couple of multi-pin plugs in the right-hand side as you view it from the passenger seat/footwell).
The ECU does not need to be removed (but it is easier to get to the CO pot if you do) - to remove it, loosen the 2 x 10mm bolts at the bottom, then ease it forward (towards you) out of its frame.
The actual CO pot is a blue rectangular thing secured to the ECU frame by one of the phillips screws which holds the frame to the dashboard. It is about 2" x 1" x 1/2" and had a plug on one end which has 3(?) wires going into the loom.
On the pot is a small slotted screw which is the adjustment.
There are no 'end stops' on the screw, so it will keep on turning, past where the movement makes any diffence to the settings.
There are about 20 full turns (IIRC) of adjustment in the pot, so a small movement may make little difference. (just remember to count how many turns you have made so it can be put back as it was if you need to!)
Personally, i found it easiest to remove the pot from the frame, adjust it, and then re-fix it again, but if you have very dextrous fingers, I suppose it is possible to do it all in situ without moving the ECU.
I used a Gunsons Gastester digital, which is straightforward to use, but takes about 10 minutes to 'warm up' before you can do any adjusting - just the right amount of time to check/re-set the base timing and engine idle speeds

.
Once it has warmed up, and is calibrated, the readings are very accurate. The box says + or - 0.5% CO, but i did mine just before taking it to the MOT garage, and set it to 2%, their (calibrated) machine says it was 2.1%.