Hi all,

I'm hoping someone will be able to point me in the right direction to get my car back on the road - recently failed Mot with a couple of issues. Most I can deal with, but the one which worries me is the failed emissions tests: around 1.9% CO, 0.94 lambda, 336ppm HC. Pass is 0.3% CO.

The car is a 1995 X300 XJR, with around 197k on the clock. It's a manual gearbox, with stainless exhaust (loosing the first cats, but keeping the 2 lambda sensors before joining into the original second cat). It's fitted with LPG, but this is obviously switched off for the emissions testing.

I've had the plugs out and done a compression test (results below) and the plugs look OK for gap and general condition. The front and rear cylinders (1 & 6) are running rich though (black deposit on plugs). Air filter is OK - it has exactly the same emissions results with the filter removed... I've also had the coil/plug cover off with the engine warm at night, and couldn't see any evidence of arcing / sparking around the coil heads.

Compression tests were (from front to back): 9.8 bar (black plugs); 8.9 bar (plugs OK); 9.0 bar (plugs OK), 9.4 bar (plugs OK), 9.0 bar (plugs OK); 9.8 bar (black plugs). Testing was done cold.

Any advice appreciated - what can cause what I'm seeing?

Thanks,

Andrew Wilde

 

Have you got an OBD code reader?
There's a whole post on them here
https://www.jaguarforums.com/forum/g...-%2A%2A-33347/
You might want one that does fuel trims but just basic codes would help.
On XK's there's only one convertor. If you have two I'm not clever enough to know what removing one will do.
Someone else will be, though.

 

[QUOTE=andrewwilde;570472]................ recently failed Mot with a couple of issues. Most I can deal with, but the one which worries me is the failed emissions tests: around 1.9% CO, 0.94 lambda, 336ppm HC. Pass is 0.3% CO.

The car is a 1995 X300 XJR, with around 197k on the clock. It's a manual gearbox, with stainless exhaust (loosing the first cats, but keeping the 2 lambda sensors before joining into the original second cat). It's fitted with LPG, but this is obviously switched off for the emissions testing........../QUOTE]

Andrew,

Has it passed an MoT since the exhaust system was modified?

Graham

 

A sensible question if ever there was !
Are there two cats on XJs then Graham?

 

It's a 1995 car - the various websites I've seen say post 1996 for US cars, and post-2001 for European cars. Will one of these work with mine? And if so, where's the connection likely to be?

I've looked down by the bonnet release catch, as per some posts on here, but there's nothing there. There's a connector in the DS footwell near the radio, looks like the attached image - is that it?

 

That's it.
If you look at the OBD posts you'll see a number (eg #2) that do work with older cars.
What about Graham's MOT question?

 

Graham,

Yeeeeees. They did note that it was hard to get through emissions, but that they got it to pass.

I say yes with a little lack of certainty, as I was out of the country for 6 months when the MoT was taken, so wasn't present. They also knew I'd be moving from the area when I got back, and were looking after the car for me while I was away. They had to do a bit of work (corroded brake lines, etc) which came to quite a bit, and emissions failing may have taken it over the perceived value of the car. I assume it was done properly, but can't say for certain.

Other than that one last year, no, it hasn't.

I suspected these lambda sensors, but can't get at the connectors to change them over and try - they're behind the rear of the engine, and I can't get my (oversized) hands down there to swap them over. The sensors themselves are accessible if you get the car on a ramp, but I don't know how many turns the cable will take before they damage, so haven't tried... It's not far to the first cable clamp, which I'd have trouble accessing on the drive...

The fact it's only 1 cylinder per bank of 3 that's showing rich on the plugs confuses me - if the front 3 were rich and rear 3 were lean, it would be a no-brainer. Unless it doesn't work like that?

 

Cool, thanks for this. What's the difference between the type of one you find on e-bay (typ. £15-30) and the full AutoEnginuity $250 plus ones? Will the latter enable cylinder by cylinder fuel injection mapping to be adjusted?

Ta,

 

Basically the EBay ones (I bought one) just give the fault codes and reset CEL.
They may claim to give live data (RPM, fuel pressure, fuel trims etc) but they don't.
There's a very good Android app called 'Torque' that does everything.
The problem is finding a cheapo Bluetooth OBD interface that works. I couldn't but if you can that is the cheapest and best solution.

 

The scan tools in the £15-30 range will read Pxxxx Codes and (usually) allow you to clear the MIL.

The full AutoEnginuity with Jaguar Expansion pack at £408.41 inc delivery is the nearest you can buy to the Dealer WDS (Worldwide Diagnostic System) and allows you to read and clear P, B, C and U Codes as well as monitor the OnBoard systems.

You can't change the fuel mapping without reprogramming the ECM.

Graham

 

Call me cynical if you must, but I'm a bit doubtful of the authenticity of that pass. You could well be trying to get a vehicle through current emissions requirements which hasn't genuinely passed since the exhaust mods.

Graham