Thread: How to improve 4.6 economy

Originally Posted by Keithy P38

That's insane! Even around town ill get 550km before the fuel light says hello! And when I fill its usually 80 litres that goes in... On average ill fill at 600kms, sometimes more, sometimes less... I think I worked it out to be a 15L/100km town average and 12L/100km highway average.

That's a Bosch 4.6 with 240,000km.

If you want to do something to the injectors and don't change them, I'd be getting them professionally cleaned at least!

That said, is there another aspect of your motor that may also be contributing to the high fuel consumption?

Cheers
Keithy

I agree it is insane. I put the car in to a well known workshop for Landies here in Perth and they said there was no issues with the car.
I knew it was high but just thought it was normal for Range Rovers having never had one before. I run injector cleaner fluid about every six months but that only makes a little bit of a difference but not much.

Originally Posted by RobboLFC

I agree it is insane. I put the car in to a well known workshop for Landies here in Perth and they said there was no issues with the car.
I knew it was high but just thought it was normal for Range Rovers having never had one before. I run injector cleaner fluid about every six months but that only makes a little bit of a difference but not much.

Wouldn't be a workshop south of the river, in a suburb starting with the second letter of the alphabet by any chance, would it?

...

Lovely chaps...

3.9L V8 on heat - is this normal?

... post 30 is the reason I'm my own mechanic these days!

Originally Posted by cal415

not much better(possibly almost the same) without the trailer... it just guzzles the juice, it smells very rich at idle too i have noticed.

If you can smell fuel I'd also have a good look at the fuel pressure regulator and for leaks in the fuel delivery hose before it joins the fuel rail...

Definetly no leaks but it is running very rich, it seems to have taken a turn for the worse again, last tank was about 320km, but that included a bit of off roading but not heaps.... whats the best method for checking fuel pressure reg on one of these?

Hi cal415
I doubt there's any simple way to test the fuel pressure regulator other than replace it with a known serviceable item and check for a difference in performance... damned expensive option however for a "yes/no" answer! last check (GEMS) was about $180+ locally for said unit... Unlike the GEMS engine where the regulator is reasonably accessible on the driver's side of the engine, the Thor engines have the regulator incorporated in the pump assembly ...in the tank.

EDIT: just had a thought .. the injectors may be quite OK. It's running rich because the injectors are being "commanded" to let in more fuel by the ECU. The ECU calculates oxygen content of the air as determined by the MAF taking account of the ambient temperature as well as fuel temp.

The ECU "thinks" that there's too much air i.e the air/fuel mix is running "lean" so it's enriching the mix accordingly. The fuel odour at idle tends to confirm this. I 've only had a cursory glance at the posts to date, but MAF and air/fuel temp. sensors don't seem to have been discussed. The sluggish engine response you reported is one symptom of a MAF needing attention. It might just require a squirt of MAF cleaner to remove accumulated crud off the sensor wire (non-residue disc brake cleaner will perform the same job at a pinch DON'T USE WD40!!)... careful, the sensor wires are fragile.

Have a look here for details and pics of how to , on a GEMS set up http://www.rangerovers.net/forum/7-r...nsor-pics.html

Check the temp sensors also for proper connection. Have a look also as to whether there's any accumulation of oil in the throttle body housing... i.e. the PCV set up may also need attention.

Good luck with it..!

I don't have a 4.6, but on other EFI engines (petrol or diesel) disconnecting the MAF forces the ECU to use lookup tables for what the airflow is expected to be based on throttle and rpm.

If the engine gets better with the MAF unplugged, then it's time to look harder at the MAF. If there's no difference, then look elsewhere.