Thread: 98 D1 V8 bad fuel economy - 43.2L per 100km - vacuum advance?

Originally Posted by Young Angus

Wow...don't suppose you've checked for leaks in the fuel tank or lines have you? Had to ask

That probably would have been a simpler to find issue!

I put the fuel economy in the title as otherwise I figured the first reply I would receive would be "of course it is, it's a V8" or something to that effect.


On a side related note - do these things benefit from the MAF being cleaned?

I read that there is a idle mixture adjustment screw on the MAF, out of interest, whats the process for tuning this?

Originally Posted by twr7cx

On a side related note - do these things benefit from the MAF being cleaned?

I found it made a difference on mine. Only get "MAF Cleaner" nothing else.

If you're towing, I also recommend the Tornado chip if you can afford it. Chip, service (plugs, leads, dizzy cap, rotor, vacuum advance unit, air filter) and 10-12 degrees of advance, it now tows way better. I'm getting 22l per hundred, down from 35 per hundred around town.

Originally Posted by twr7cx

That probably would have been a simpler to find issue!

I put the fuel economy in the title as otherwise I figured the first reply I would receive would be "of course it is, it's a V8" or something to that effect.


On a side related note - do these things benefit from the MAF being cleaned?

I read that there is a idle mixture adjustment screw on the MAF, out of interest, whats the process for tuning this?

At operating temp and idling, stick multimeter probes one in each wire at the furtgest outer ports left and right of the maf plug. Dc volt setting you need to see about 1 to 1.1v. Turning the screw clockwise increases the voltage, decrease antixlockwise. Higher the number tge richer it is

Originally Posted by justinc

😅😅 you diesel boys have no idea how bad it can get😎😅

Haha it was a genuine suggestion...well, I was having a bit of a chuckle while I wrote it but before I owned my Tdi I owned a '98 V8 Disco and for the life of me I can't remember it being anywhere near that thirsty.

Assuming you Disco 98 has fuel injection - May I suggest you look at the performance of the O2 sensors and the MAF. I've recently had issues on my 2001 V8 with performance and fuel consumption. Both fixed when I dealt with these components. BTW I've never had a consumption figure at 42l/100K. The worst I've had is 22l/100K

Are you sure the hand brake is fully released or that you don't have binding calipers - all obvious I guess.

All the best.

Just out of curiosity what is the MAF reading supposed to be on a 4l V8 at idle?

Originally Posted by John R

Assuming you Disco 98 has fuel injection - May I suggest you look at the performance of the O2 sensors and the MAF. I've recently had issues on my 2001 V8 with performance and fuel consumption. Both fixed when I dealt with these components.

I believe that the D2 and D1 V8 fuel systems are significantly different. I don't recall noticing oxygen sensors on the D1 and a quick Google search seems to indicate that they didn't have them.

Originally Posted by John R

Are you sure the hand brake is fully released or that you don't have binding calipers - all obvious I guess.

No signs of excess heat on any of the components to indicate seized items.

Is the engine down on power? Have you had any signs that the engine may have cooked at some stage?

After checking the obvious (MAF, VA, Rad/coolant/ fuel/oil filter etc) and if no improvement then generally this begins to point at some blow by in the system and fingers crossed not, but could be an issue with losing compression via worn rings, valve guides / valve stems or even a blown or near blown head gasket.......which means getting down there re-building.

The Buick is a very simple engine on these V8's with no Lambda (Oxygen) so it wont be that either.

It's not uncommon for these engines to run very rich and are susceptible to a heavy right foot too, around 20-25/100 is achievable on the open road with a tail wind, more like 25-30 or worse more around town.

A wise man once quoted a proverb on this forum "V8 go past everything except petrol station". Consider getting LPG conversion off a wreck if you're trying to save cash...