My second Jag has been on try drive for few days now and bet you me, it has a crazy gas consumption than the first one she came to meet.

could there be anything probably wrong that may cause this higher fuel consumption?

Need your help to get this solve to save my pocket 😂.

 

It might be that the fuel injection system has a fault, sending too much fuel to the cylinders:

XJ6 Series - EFI Rich Mixture

Other thoughts:

Incorrect ignition timing
Dragging brakes
Clogged catalytic converter
Misfiring cylinder(s)
Clogged air filter

Cheers
DD

 

This may be a shot in the dark, but some time ago I had an episode in which the SIII fuel mixture went so rich that the car would barely run. It took a while but we traced it to a pink wire in the trunk that was disconnected. The wire runs from the air flow meter to the trunk location then to the ECU to regulate mixture. It has a connection in the trunk because there is a seldom installed high altitude switch there that sends the signal to a separate high altitude input on the ECU (terminal 12) above about 4200ft MSL. Normally the two pink are connected and carry the air flow sweep directly to the ECU (terminal 9). If they are not connected, the ECU thinks infinite air coming in and feeds as much fuel as possible. That is the extreme case, the car won't run well. I suppose if there is a problem with the air flow meter the ECU could be seeing something in between that would enrich the mixture with more fuel, but still allow the car to run.
The service manual says that the air flow information is the angle of a flap opened by air passing thru the device. It doesn't indicate the nature or range of the signal. It could be a resistance or a voltage. Neither does it say how to check for correct operation. If anyone knows how to check I'd be interested as well.

 

Other thing that is possible is the changeover valve between the fuel tanks is sticking. For example, say you have selected the right tank, but the fuel is returning to the left tank and fills it. Fuel keeps returning to that tank and then the fuel is pushed through the vapour return lines to the intake manifold and floods the car.

I think if you take a thin screwdriver and look into the filler neck while holding the litter flap down in the filler neck open you can see the fuel returning. Make sure it's going to the correct tank.

 

There is also a fuel smell scent in the car when the engine is running and the exhaust fumes smell the petrol scent like the petrol doesn't burn and comes out raw.

 

Based on that I'd go right to he 'overfueling' checklist linked above.

Cheers
DD

 

Doug

Please how do I know if the catalytic converter is Clogged?
WHat is the solution to fix the Clogged cat converter?

 

Clamp off the fuel line to the cold start injector while idling to see if the idling improves. If it does then you have found a stuck open cold start injector.


Larry Louton

 

Low power is the most obvious clue

Quote:

WHat is the solution to fix the Clogged cat converter?

Replacement.

Or remove and knock out all the innards with a hammer and long piece of metal rod

Or remove and replace with straight pipe

Cheers
DD

 

Thanks Doug
I will check and remove the cat converter, I will not put straight pipe but we usually replace the removed converter and replaced with folded paultry wire mesh.

I forgot to mention, that the oxygen sensor light is on from time engine start till after journey when engine is off.

Could that be as result of the clogged cat converter?

 

As you wish. But that won't solve your problem of almost raw fuel coming from the exhaust.


That light comes on every 30,000 miles as a reminder to replace the oxygen sensor. You oxygen sensor might, or might not, be faulty. If faulty it might be part of your excessive fuel usage.

The trigger unit for the warning light can be reset so the light will turn off.

Cheers
DD

 

thanks boss
please what's the best solution to eradicate the problem of raw fuel smell coming from the exhaust?

Where do I rest the trigger unit for the warning light to turn off?

 

Am the the Jaguar expert shop to work on the cat converter but the observation reported the the the cat converter has already been removed

 

Click on this link for ideas:

XJ6 Series - EFI Rich Mixture

Quote:

Where do I rest the trigger unit for the warning light to turn off?

The trigger unit is in the trunk. I'll try find a picture

Cheers
DD

 

Hi Doug
I have changed the ECU, air filter element, sampapered the temperature sensor to clean the dirt from it.
Please which of these in the photo is the trigger unit?

 

It's the box-like unit shown clearly in pic #3. In pic #1 it's the unit all the way over to the left. There's a little button. Use a pointy tool (like a nail or ball point pen) to push the button. You'll hear a click.

This will extinguish the warning light but has no effect whatsoever on how the engine runs.

Cheers
DD

 

Hi Doug,
Per your instructions and procedures, I have been able to reset the oxygen sensor and the light is off now

 

It may not apply so much to the 6 cylinder cars, but, for V12s, failure of the vacuum advance capsule raises fuel consumption by about one third. And, apart from the more frequent need to re-fill the tanks and the reading on the computer, everything runs pretty normally.