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[Gaffers]

Looking at my fuel consumption this evening I get the feeling that my fuel trims are waaaaaaaaaaaaay out on the jaaaaaaaaaaaag.  It is consuming a lot more fuel than it should, I know it guzzles but still there's a limit.

Anyone know how to reset them without going down to the stealers and getting raped?  I have a maxiscan which can read the trim but not sure if or how it would reset them....

[Lazydocker]

It's a Jag... Bend over and take it dry

[Manual Elite V6]

If I recall correctly it is an option only for someone with the right diagnostic equipment, however sometimes you can sort it yourself but not always by swapping the lambda sensor plugs over run the engine for a few minutes then swap them back, sometimes this will reset it for you but more often than not it doesn't work.

You could also try a hard reset of the ECU by disconnecting the negative lead from the battery and touching it to the positive for 10-30 seconds.

[2woody]

if its any consolation, I've NEVER seen more than 16.8 mpg in mine, even on a run at 60mph.

on track, it drops to an average of 6.7 mpg

[Kevin Wood]

Can you see the fuel trim values? Are they excessive?

The problem with resetting them is that if you haven't fixed anything, they will end up exactly where they were the first time you drive it again. If it's trimming the fuel it's because it needs the fuel, or thinks it does.

[BazaJT]

It depends on how you're classifying "guzzles",my 3.2 AJ16 engined Jag recently averaged 26.8 mpg on a 450 round trip run,however just running the dragonlady to her bingo and back sees it averaging a figure of 10.4 mpg as it's only a 2 mile round trip.Not sure about the XJR but my car doesn't hit top gear[4th]until just short of 50 mph so round town consumption figures can be horrendous.If needed I would go for an independant specialist rather than a main dealer,significant savings can be made this way.

[dbug]

My '04 XJ6 (X350 Aluminium body) on a 350 mile round trip mainly motorway with some minor/town roads gave 29.7 mpg (average speed for the trip around 70mph).  Short runs and round town average 21 mpg.

[Gaffers]

I found the issue.  A snapped bolt on the down-pipe to manifold was causing a blow, you couldn't hear it but you could feel and see it once the heat shield was removed.  Manifolds were removed the bolts drilled out (the other one snapped on removal) and all replaced.  Reset the computer and went out on a spirited run.  Mpg has come back to normal-ish.  Hopefully the trims will adjust more over the next couple of days until I see 22mpg again.  It was down to 11, on a lon run