Emissions as a sign of fuel mixture

[peterjohn77]

Sirs

My recent MOT has highlighted a significant difference in the CO content between the banks, even though they didn't need to do the test for the age of car. The Service Manual advises that tool 60730551 is required, I am assuming in conjunction with the emissions testing equipment.

Is this tool available. Is this the only way to get the right fuel mixture? How sensitive is the measurement in the 1st place.

Regards

Peter

[ptjs1]

Peter,

What year car do you have? All XJSs have to have MOT emissions tests of CO & Hydrocarbon particles as the tests apply to all vehicles first used after 1/8/75.

1975 - 1986 cars have MOT limits of 4.5% CO & 1200 ppm HC.
1986 - 1992 cars have MOT limits of 3.5% CO & 1200 ppm HC.

What sort of figures did your car have in the test?

Paul

[peterjohn77]

The car is a 78.

The actual reading are:

R Bank 1.2% & 131 PPM
L bank 2.4% & 492 PPM

It is clear the L bank is outside of the 2% limit from the service manual and the HC content is a factor of 4 different between banks

[Hosier77]

The fuel injection system puts the same signal to the injectors on both sides, so the chances are that it is simply that the throttles are adjusted slightly diferently from side to side, probably nothing to worry about as it only effects idle and very light load. Try tweeking the throttle stops and linkage and see what happens to the emissions.