Weak mixture-cyl 1,2,3 and engine control module. 04 xjr

X300
1

This is a 2004 XJR, new to me. Sounds fine at low speeds, but then had a hard miss with 1/2 or full throttle. Engine light is on “restricted performance”. Code reader gave codes P0171, (twice) and P1111
It said "weak mixture cyls 1,2,3 for P0171 and Engine control module for P111.

The above is all greek to me. Is there anything I can do before making a 70 mile trip to the dealer?

Thanks.
Wayne

2

I’d start by pulling the plugs and checking the gaps and their colour and/or work from there wire brushing, regapping etc. or replacing the plugs if neccessary.
It’s worth suspecting coils if any plugs are badly fouled and see how it goes from there. A pain in the butt to do but there it has to be!

3

Neil,
Thanks for your reply. I’ll get serious in the morning. The car ran fine a few days ago in FL. It was delivered here (Northern NY) this morning in cold weather. It was a FL car, would that have anything to do with computer/control module? PO just did new NKG Iridium IX plugs less than a year ago. When I first started the car there was a lot of white smoke. Then it turned normally clear with the miss.
Just wondering about that. I did a code reading, then cleared it, and it ran fine for a while, then started missing again.

Is it possible that a vacuum hose came off?
Thanks again.
Wayne

4

Hi Wayne,
I suppose anything is possible, the vacuumn hose could be off or the plastic parts fractured as that is not unknown.
Simon Sparrow’s go-lpg web site Common XJ faults has much on plugs and the gapping thereof.