Poor fuel economy, MAF related?

[wheelnut]

Just got myself a replacement MAF as I think mine might have problems.

Also at the moment I would seem I am only getting about 120 miles to a tank, does any one know or think this could be related to a faulty MAF or should I be looking for something else as well.

There is no obvious fuel leak and when parked for 36 hours the needle didn't move. but you can practically see it drop whilst driving even at slow speeds.

Will of course fit the replacement MAF and report back.

[Confused]

How are you driving for that 120 miles?

How much fuel are you putting in after 120 miles?

The fuel gauge on the Galant/Legnum are notorious for being woefully inaccurate!

[Turbo_Steve]

Very unlikely to be the MAF, and far more likely to be the lambda sensor if you're overusing fuel at cruise.


Unfortunately, diagnosing fuel problems requires you to fill up, do a specific number of miles, and fill up again to measure the amount of fuel you've used, and then work out the mpg. The fuel gauge is absoloutely useless: no two cars are the same, and the position of the needle bears no resemblance to the contents of the tank.

Also, please define "slow speeds".

85mph cruise is actually quite thirsty on a VR4. 60mph cruise seems more reasonable.
Round town, these are heavy, 4wd, probably automatic cars, and as such they are pretty ropey on economy if you're stop/starting a lot.

Flat out, they're only marginally more thirsty than your average 270bhp turbo'd car.

[Dom B]

On the gauge even down to about an 8th of a tank you probably have only used 40l of fuel as the gauge is awful. I usually see about 180 miles to this point with the awful inaccurate fuel gauge. Like the guys said do a full fill up, reset the trip meter and the when empty fill up to the top again. Divide your fill up litres by 4.546 to give you the number of gallons used and then divide your trip mileage reading by this number of gallons to get your mpg.

[Subaru ETA]

maf could cause poor fuel economy - if the idle is all over the show because of it it would be trying to compensate by pissing with the fuel maps

[wheelnut]

Thanks for all the responses.

To be more specific the needle has dropped from half to a quater after driving 30 miles mostly at crawling through town speeds, I guess about 10 miles of it was doing a steady 50.

So I could be jumping the gun by the sound of it, if the indicator is massivly inaccurate, but it is almost back down to where it was before putting £20 of super unleaded in.

As for the MAF thing, at the moment the idle speed is a nice constant 650-700 so that probably isn't causing to much grief.

Will take you advice, stop worring for now and fill it up and do a proper test.

Cheers.

[miller]

Thanks for all the responses.

To be more specific the needle has dropped from half to a quater after driving 30 miles mostly at crawling through town speeds, I guess about 10 miles of it was doing a steady 50.

Standard VR4 practice! just when your sitting comfortable on your journey thinking yeah its not too bad, seeing 60clicks on the mileometer and a 1/4 tank used

then comes the dreaded DROP to a 1/4 tank

Like Steve says measure your fuel consumption on fuel fill ups to the first click at the pump


Mike

[Turbo_Steve]

maf could cause poor fuel economy - if the idle is all over the show because of it it would be trying to compensate by pissing with the fuel maps

Sorry, yes, you are quite correct in this, however I ruled out MAF issues as I automatically assumed the post would have been "Car running like complete bag of cack", and we all know what assumption does, don't we?