CO adjustment - Revision history

Fredjohn at 15:42, 17 August 2016

2016-08-17T15:42:27Z

Geoff at 19:52, 24 April 2013

2013-04-24T19:52:20Z

Ashm at 19:02, 1 March 2011

2011-03-01T19:02:24Z

Dapinky: New page: Make sure the car is warm before you start Put it into service mode - start the car first, then put in the paperclip (otherwise it is in diagnostic mode). To locate the CO pot:- open th...

2008-07-31T08:37:09Z

New page: Make sure the car is warm before you start Put it into service mode - start the car first, then put in the paperclip (otherwise it is in diagnostic mode). To locate the CO pot:- open th...

New page

Make sure the car is warm before you start

Put it into service mode - start the car first, then put in the paperclip (otherwise it is in diagnostic mode).

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 :D .

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 :D .

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%.

Remember that current regs for the UK state that the CO level must not exceed 3.5% for the SE/NA, and 1200ppm hydrocarbons.
With the S2, the acceptable CO levels drop to a lot less!

← Older revision		Revision as of 15:42, 17 August 2016
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	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 dexterous fingers, I suppose it is possible to do it all in situ without moving the [[ECU]].		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 dexterous fingers, I suppose it is possible to do it all in situ without moving the [[ECU]].
		+
		+	EDIT ADDED: Turn the screw clockwise to make it richer/raise the CO reading, anti(counter) clockwise to make it leaner/lower the CO reading. (Fredjohn Aug 2016)

	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.		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.

← Older revision		Revision as of 19:02, 1 March 2011
Line 27:		Line 27:
	Remember that current regs for the UK state that the CO level must not exceed 3.5% for the SE/NA, and 1200ppm hydrocarbons.		Remember that current regs for the UK state that the CO level must not exceed 3.5% for the SE/NA, and 1200ppm hydrocarbons.
	With the S2, the acceptable CO levels drop to a lot less!		With the S2, the acceptable CO levels drop to a lot less!
		+
		+	<ashm> The CO Pot is a variable resistor, with a range from 270 to 10,500 Ohms measured across the two outer pins. The centre pin does not appear to be connected to anything in the Pot housing. The range is covered in 20 turns, with clockwise adjustment increasing the resistance (these details are true for my H-reg SE, anyway).

@@ Line 3: / Line 3: @@
 Put it into service mode - start the car first, then put in the paperclip (otherwise it is in diagnostic mode).
-To locate the CO pot:-
+To locate the [[CO_pot|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 :D .
-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).
+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 [[ECU]] does not need to be removed (but it is easier to get to the [[CO_pot|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.
+The actual [[CO_pot|CO pot]] is a blue rectangular thing secured to the [[ECU]] frame by one of the Philips 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 2 (Turbo) or 3 (NA) wires going into the loom.
-On the pot is a small slotted screw which is the adjustment.
+On the [[CO_pot|CO 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 no 'end stops' on the screw, so it will keep on turning, past where the movement makes any difference 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!)
+There are about 20 full turns 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.
+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 dexterous 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 :D .
+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%.
+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%.
-Remember that current regs for the UK state that the CO level must not exceed 3.5% for the SE/NA, and 1200ppm hydrocarbons.
+Remember that current regulations for the UK state that the CO level must not exceed 3.5% for the SE/NA, and 1200ppm hydrocarbons.
-With the S2, the acceptable CO levels drop to a lot less!
-<ashm> The CO Pot is a variable resistor, with a range from 270 to 10,500 Ohms measured across the two outer pins.  The centre pin does not appear to be connected to anything in the Pot housing.  The range is covered in 20 turns, with clockwise adjustment increasing the resistance (these details are true for my H-reg SE, anyway).
+With the S2, the acceptable CO levels drop to a lot less but are set by the [[Oxygen_(Lambda)_sensor|Oxygen / O2 / Lambda sensor]] so doed not have a [[CO_pot|CO pot]]!