My 2001 XJR started to smell a little rich (to say the least) and I discovered two fault codes (P1646,P1647). I took it to my mechanic, who is very experienced on Jags from this era, who replaced all 4 oxygen sensors. Both fault codes were rectified. He said the sensors were black with soot - which he'd not seen before.

The car is running a little rough when idling (in any of PNDR), more so when it warms up I've noticed. My mechanic has said that it's not possible to reset the ECU on this particular year XJR so it will just need to learn and adjust. It's been three weeks now and it still has regular erratic idling.

Can it take this long (at least 200km driving motorways/city) for the ECU to retrain with the new sensors?

Obviously I'll get back in touch with my mechanic but just wanted to see if anyone had any sagely advice

BTW: I can monitor the sensors via my Torque app but am not really sure which to look at The app has 8 sensors, not all of them are showing activity, and each sensor has:

• Wide Range Current
• Voltage
• Wide Range Equivalence Ratio
• Wide Range Voltage

 

Have you got (pending) P1000 or P1111?

If P1000, many codes cannot flag so you may end up guessing...

 

Check the fuel trims, you may be running too rich or lean.

 

Ecu is possible to reset. But you need ids for it. It wil adjust itself back to normal state in couple drive cycles. Unless there is fault(s) of course.

 

Hi Vauxi, are you 100% sure about that? My mechanic used to work with Jaguar in the UK when these models were released - and he said that this particular year/version ECU it was not possible to reset.

 

There are no fault codes.

 

These cars always have either P1000 or P1111. If your tool doesn't show either, change tool or its settings.

 

Oh, I see - these codes [put very very simply] mean pass or fail, but it has to be one or the other? I just use the Torque app with the OBD2 but my mechanic has said there are no fault codes showing when he scans it.

 

you can flash program them with the right tools but the only day to day task you need is to pull the fuse/unplug battery to reset your trims.

 

If the spark plugs are new and especially if they are iridium plugs, you may have a vacuum leak. Check the plastic hoses that go to the throttle body and the manifold under the throttle body. Also, check your oil cap gasket. High fuel trims will be a sign of vacuum leaking and these cars are very sensitive to this problem. Make sure the little hole under the plastic hose on the oil fill side valve cover is clear as well.

 

One of my 2000 VDPs had a skip when idling at operating temp. The car would do this especially if in drive while stopped by the brakes. I did a lot of fooling around with no avail until I swapped all the coils from my other car and then the problem moved to the other car. Then I swapped coils until i located the faulty one and replaced it. When measuring the faulty coil with an ohm meter, it had similar readings to any other coil so I did not expect the coils were the problem. I also had a rough idle problem some time back that turned out to be a crack in one of the plugs.
Just a thought....

 

Thanks everyone for your comments, just in case it wasn't clear - prior to the oxygen sensors being replaced, the car [while running rich] idled very smoothly without any coughs/surges

 

But it's likely the air intake system was removed when replacing the sensors. At least look for cracks in the accordion section.

 

P1000/P1111 are status codes, confirming the state of the OBD monitors (you can read those instead but it's quick to see which of P1000/P1111 is there).

They're not fault codes (in this case) - any P1xxx code on any car is non-generic i.e. the car maker can have them mean absolutely anything (so you need to look them up in that car's info, which in this case you can download free from this site or JagRepair.com - Jaguar Repair Information Resource).

 

Okay, so and update for anyone interested

After being away and too busy to get this looked at, I'm booked in to have it checked by my mechanic on Monday.

Worryingly, he made this comment:

I said something like, wouldn't be a big coincidence if a problem developed with the catalytic converters at the same time the oxygen sensors were replaced?

...hopefully it's something simple ​​​​​​​
​​​​​​​

 

I'm not 100% sure but my yo2000 xjr was possible to reset via ids. Sorry for delayed answer.

 

Hi, did you get this fixed? I have he same kind of issue after an O2 sensor change.
Thanks

 

It's quite a long thread with multiple things raised - so which exactly apply to your car?

Common issues include using the wrong sensor type or replacing the wrong one...

 

Timing chain tensioners (slipped timing) often cause a rough idle.

 

Using aftermarket O2 sensors can also cause rough idle. I replaced mine with eBay sensors and they were garbage, ran way worse. I swapped back in my old ones and the rough idle went away.