X300 Failed MOT on emmisons, help!

[redvtec]

I have a XJ6 3.2 X300 Executive. I have always had issues with emissions, over the past few years the car has had new cats. new 02 sensors, and then the sensors rewired as a garagre reckoned they had been plugged in back to front.

Yesterday it failed on emissions the readings are:
Reading Limit
CO %vol 7.363 0.300
HC ppm vol 338 200
Lambda 0.800 0.970 - 1.030

I have pulled the plugs and three of them look slightly black which would indicate a rich mixture. These are all on the same bank of 3 cylinders, could this be the cause? if so any suggestions what to do?

Many, many thanks

[Ecurie Ecosse]

Do the injectors need cleaned maybe?

[rswift]

Lambda sensors would be my first point of call, are the new ones proper Jag ones, or just generic ones !...Jag ones are expensive ....but you can get them cheaper from the specialists. Swapping the wires by mistake seems to be a common problem

I would suggest finding a local indie Jag place to check it out...probably cheaper in the long run, whereabouts are you ?

Also have a look on the Jaguarforum.co.uk

[redvtec]

Thanks for the replies, I have supposidly had a jag specialist look at it, he fitted the cats and 02 sensors. I pulled the plugs and it appears to be running rich on one bank of cylinders. this would cause the emissions, but what is causing it to run rich?

[cptsideways]

redvtec said:

Thanks for the replies, I have supposidly had a jag specialist look at it, he fitted the cats and 02 sensors. I pulled the plugs and it appears to be running rich on one bank of cylinders. this would cause the emissions, but what is causing it to run rich?

A faulty signal from the lambda probes will make it run rich. I'd be inclined to buy a cheap narrowband gauge, wire it in & see whats showing.

Is there an engine management on?? as their should be if the lambda's are duff. Is the engine management light visible on startup?

[redvtec]

Hi, It would appear that I have a dodgy coil pack, I'm going to replace this and see what happens, as it is misfireing which would cause emmission issues.

There is no Mangement light showing on the dash.

[cptsideways]

redvtec said:

Hi, It would appear that I have a dodgy coil pack, I'm going to replace this and see what happens, as it is misfireing which would cause emmission issues.

There is no Mangement light showing on the dash.

The coilpack should return a misfire signal to the ecu & flag the mil light

[redvtec]

I have replaced the faulty coil pack and the plugs are all now a brown colour indicating they are running correctly. rather than black and oily as before. I will get the emissions tested again and report back.

[ringram]

cptsideways said:

The coilpack "should" return a misfire signal to the ecu & flag the mil light

Depends on how bad it is. Weak spark as opposed to no spark might not trigger it.