Thirsty EFI

K

KiwiRover

Active Member
This is slightly off topic but not entirely. A few months back, my brother purchased a '97 Discovery for the wife to drive, a Red ES with the 3.9 and auto and about 180,000kms on the clock. She adores the thing but they soon discovered that the fuel consumption was abysmal.
Not just 'V8 4wd' abysmal but seriously bad. It ran ok, but for the occasional misfire but never managed to achieve more than 280kms from a tank of fuel. I had a 3.5 disco years back that did 450-500kms per tank and the local Landy specialist reckoned that it should get a comfortable 400kms per tank even around town.
I am fairly unfamiliar with the efi so he took it to the Landy guys who took a quick look under the bonnet and discovered that- a: the serpentine belt had been creatively routed and the water pump was running backwards, and b: several of the minor vacuum hoses had also been randomly fitted including the cruise control and fuel pressure regulator.
They fixed these and sold him some injector cleaner to put in the tank, but said that as it had probably been running with excessive fuel pressure for god knows how long, chances are the valves would be all carboned up and would probably be the cause of the intermittent misfire. Unfortunately their tweaks didn't help so we bit the bullet and I pulled the heads off. There was not massive amounts of carbon buildup on the valves but the valve seats were pretty poor so we had the valves ground. The reconditioner said it had 4 slightly bent valves!
All was reassembled, cleaned and tidied and the engine runs beautifully. Smoother with a bit more power and sounds great. :) However, the fuel economy is still exactly the same. :x He has brought it back in to work to tidy it up and prepare it for sale but I would really like to be able to fix it for him. He did casually mention when he brought it in that it doesn't actually shift into 4th gear 'til 80kph! I checked and found the kickdown cable to be overtightened by about half an inch so I fixed that but I don't know if that would be enough by itself for a vehicle that rarely sees the motorway in regular use.
I spent a bit of time fiddling with it this avo and put a colourtune plug in it which showed a perfect flame, also, it doesn't blow any smoke so I am fairly certain that the engine is not the issue but I'm running out of ideas.
Any thoughts, good people? :)
 
Hello KR,

The waterpump on a serpentine engine does indeed spin in the opposite direction to that of a non serpentine engine. If the pump is now spinning in the same direction as your P6B, then that is incorrect.

Has the thermostat been changed to ensure that it is the correct one? I would expect an 88 degree or even higher to ensure that the ECU reduces the fuel mixture that is being supplied. Has the vacuum advance module on the distributor been replaced as if the diaphragm has failed then the engine will always use more fuel than would otherwise be the case. What is the ignition timing set to KR?

The filter in the power steering reservoir if in need of replacement can place an additional load on the engine thus increasing fuel consumption. The engine will also use more fuel if the camshaft and timing set are heavily worn, the latter will retard camshaft timing which has a direct effect on fuel consumption.

Ron.
 
Hi Ron, the belt was sorted by the Landy experts. It now runs under the water pump pulley which is correct. Funnily enough, it didn't seem to make any difference to the running temp. :?
I have not checked the thermostat but as the temp gauge always sits just below half, I have no reason to suspect it of being wrong/faulty. Also, having just refilled the cooling system with fresh anti-freeze, I am reluctant to drain it all again. Especially as there is no drain plug on these things.
I will check the vac advance unit in the morning. Would a duff vac advance make THAT much difference?
I'm not sure if the Disco has a filter in the PAS reservoir but I will check that tomorrow too.
 
Hello KR,

If the vacuum advance module isn't working then you can add at the very least a 10% increase in fuel consumption... :shock: They really do make a big difference.

The temp gauge sounds about right, so the thermostat is likely correct.

Which fuel grade is being used,...E10 or 95 unleaded or 98?

Ron.
 
how about trying a gas monitor on the exhaust to check hyrdo carbon emissions? and check thru-out the rev range.
Does it have a duff o2 sensor, theses are a common failure if fitted
graeme
 
KiwiRover wrote,..
I will check the vac advance unit in the morning. Would a duff vac advance make THAT much difference?
I'm not sure if the Disco has a filter in the PAS reservoir but I will check that tomorrow too.
Click to expand...

Hello KR,

Just wondering what you found,....any joy?

Ron.
 
No major progress yet Ron, the pas doesn't have a filter and the vac advance seems to work fine though. It did drop a couple of cylinders when we were moving it the other day though. I removed and dried all the plugs and it is back running on all 8 now. Anything I do may be moot because my brother is commited to selling it now and is not prepared to invest in another tank of gas to see if we've made any improvements.
 
Don't forget the simple things! Rover V8's are terribly sensitive to poor quality plug leads. And there are so many cylinders you won't notice the occasional missfire - except in the consumption! Fit a decent set of plug leads - Magnecor if the budget will stretch - and ensure they are not touching at any point with lead clips and you ought to see an improvement!

Chris
 
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