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I just went to collect my '98 XJR following a service and there is a "Restricted Performance" message showing on the dash. The engine appears to run OK, other than being a bit lumpy at low revs and with a noticeable smell of unburnt fuel at the exhaust pipes. OBD code P0102 coming up = "Mass or volume air circuit low input". Have tried swapping the MAF sensor with an identical unit from another car, but the fault is still present. This fault had not been present before the service; the spark plugs, filters and supercharger belt were all changed, but I cannot see how they might have induced this fault. Any ideas? Thank you.

Try tightening the Jubillee clips on the induction piping, John. I`ve seen that cause a PO102 on my later X350R.

The near side rear spark plug is not always easy to get to. The garage may have had to pull some plugs and sockets to get to that spark plug. I wonder if they have disturbed something around the EVAP unit?

You might also try solvent cleaning the hot wire with spray carb leaner in the MAF sensor. The wire must be bright and shiney rather than dull and black with crankcase residue. Make sure the plug and socket connections are also free of corrosion.

Mike K

Thanks Mike. Good advice - I'll follow your suggestions and check it out.

Cheers,
John.

If you have just paid someone to service the car, and the fault manifested itself when you collected it, surely it's their problem to diagnose and rectify, rather than yours.

If you have just paid someone to service the car, and the fault manifested itself when you collected it, surely it's their problem to diagnose and rectify, rather than yours.

And that's exactly what I did in the end. I'd had the car serviced intending to use it for a short break to Devon, and was really hoping up until the eleventh hour on Saturday night that we (the garage + myself) might still be able to find a fix in time. Sadly not... In the end my wife Jackie and I set off on Sunday morning in my other XJR - which has always proved 100% reliable and has never missed a beat - covering almost 500 miles in three days.

For what it's worth the "Restricted Performance" message was eventually traced to a blown 10A fuse (#12) in the small fuse box adjacent to the N/S/F suspension turret. Apparently this fuse protects the circuit supplying power to the MAF sensor. Quite what caused the fuse to blow isn't known, but once the garage had identified the fault and replaced the fuse normal performance was restored. I collected the car earlier this afternoon and drove it the 25+ miles home without incident - running like a dream Still, worth remembering that little fuse for the future!

Hi John,
Thanks for posting the outcome of the problem for us and hope you had a lovely time in Devon.
Enjoy your cars,
Andy