Greetings

My 2003 D2 V8 (4 litre) has started using excessive amounts of fuel …. Lucky to be getting 250 – 300 km’s per tank (150 – 190 Miles).

It’s not leaking fuel anywhere and the fuel gauge is reading accurately … it is not driving any different, no noticeable fuely smelling exhaust or anything else obvious.

I will be checking the Mass Air Flow Sensor and Coolant Temp Sensor, my truck has done 250k Km’s so these may need changing …. But would like to diagnose the problem first.

What is the best way to test the MAF and CTS ….?

New fuel pump 6 months ago.

Is there anything else I should check …. ?

No Warning lights on the dash …!

Any assistance and recommendations would be well received

All good

Darren

Perth Western Australia

 

I recently had the exact same fuel economy on a road trip about 2 months ago. I was getting a lean code on bank 1. Scan it even if the check engine light doesn’t turn on, there may be an intermittent code lurking in there that might point you in the right direction. Ultimately something is causing your truck to think it’s getting less air than it actually is, start with the simple stuff, vacuum leaks are a good place to start and depending on the age of your truck the upstream oxygen sensors may be due for replacement anyway (they tend to indicate a lean burn as they age out).

 

Another thing to keep an eye on with a scanner would be “long term fuel trim.” This is the percentage value that the computer is adjusting the fuel injectors by according to feedback from the oxygen sensors. Some variation is normal but there is a value at which a code will be thrown, perhaps you are just under that value and have a situation where the injectors are dumping extra fuel in to the engine but just not quite enough to throw the code.

Also...does your check engine light actually work? The previous owner of my truck actually cut it out (presumably to pass an emissions test). It should illuminate briefly when you turn the truck on as a bulb test.

 

Definitely check for trouble codes with a LR specific diagnostic tester. post them here in the forum.

Drive your Disco without the MAF wire connector connected. If the problem stays the same it usually means a bad MAF sensor.

 

.... going to start by looking for any obvious Vac leaks ..... auto transmission in park .... idling at 1000 rpm atm .... should ths be around 750 rpm ....?

 

Yeah, you need to scan for codes and monitor 02's and fuel trim, short and long...to see what's going on. I'd also be checking everything from the air intake tube in fender to the throttle body for abstructions before MAF and unmetered air entering the system downstream. Have you cleaned the throttle body or looked that ovef? How do you use this vehicle, off-road machine or daily driver (just trying to get a mental picture of what conditions it may be subjected too).

 

........ son is over with the code reader tomorrow ... so will scan and check all of the vac lines for start .... new air in take filter ....cleaned maf sensor and throttle body on the last service 5000 km's ago ..... this all gets checked and oil changed every 1000km's ... daily driver does 90% of its time of the bitumen. 250k on the chassy .....50k on the top hat linered donk................. just checking 750 rpm is the correct idle speed ....?

 

750 seems a little high for the idle. Mine is typically around 675.

 

Greetings

ok ... just came from the garage ... everything checks out and no codes ... trim is good ...oxy sensors good ....tps good ... coolant sensor - good... sprayed the start ya ba&%$d around - no vac leaks detected .... MAF is clean ....... air filter is clean - non oil type ...... no fuel smell from the exhaust .. no fuel leaks ....running 98 octane fuel as always .....

mechanic reckons to change the MAF( would have done at least 100k + km) anyway to see what happens ... and also the evap purg valve as these can cause problems ...?

on my 3rd or 4th tank of fuel from different garages .. no difference.

please, comments and suggestions are welcome ....?

All good

Darren

 

98 octane fuel ?
What’s your idle rpm now ?
You have a 4.6 litre or did you change it to the 4 litre engine ?
I would recommend you do disco mikes sticky maintenance list. Purge valve pcv mod

if your driving city you should only expect 400 km Max per tank if that.