www.jec.org.uk

I have a problem with my Jaguar XKR 2002 year. The engine diagnostic light keeps illuminating. There is no fault that I can feel on the engine, performance and fuel consumption is normal. But occasionally, typically 30-40mph under light load or coasting the diagnostic light comes on with an "Restricted Performance" warning. The light doesn't clear and has to be manually cleared with a scanner through the OBD port. The diagnostic codes are weak mixture left bank and/or weak mixture right bank.

I'm not overly worried about engine damage as this warning is coming on under light or no load - I would be if it was under high or full load. Anyone any suggestions or has anyone seen this before. My only thought was that changing the lambda sensors might help?? If so anyone know where they can be gotten at a reasonable price.

Rgds

Craig

Craig, this engine management light is only coming on as a result of the Restricted Performance warning. You need to get to the bottom of that problem. Sorry I can't be more helpful.

Damian

The P-codes are 0171 and 0174 which are lean mixture left and right banks. According to the DTC section of the JTIS database the reasons can be as follows:

Exhaust leak (upstream presumably drawing in air to give an apparent lean mixture at the O2 sensor)
Faulty O2 sensor/wiring
Faulty signal from MAF sensor
Faulty signal from engine temp sensor
Faulty signal from TPS sensor
Vacuum leak after MAF sensor
Low fuel delivery (blocked injector, low fuel pressure, blocked filter, faulty pump etc)

So it's a matter of which one to plump for first. As this happens a few miles after starting and at low load, I'm thinking of plumping for the temp sensors and/or lambda sensors. I think low fuel delivery would manifest itself at higher loads as well. But just wondering if any of these faults are more prone that others on the XKR.

Rgds

Craig

It's also possible that a dirty throttle body could produce the symptoms you describe. Try cleaning it carefully before resorting to spending money on spares. If the problem is oxygen sensors, Jaguar uses NTK units and these can be bought from several online suppliers. Mike.