Just looking for some input here but trying to get my gas milage back...
To summarize,
I have a Disco II 99
She has 158k on the clock
Tara forma lift 3"
Some what over sized tires 10.5 or so 16" rims
ARB and winch on the front
Custom rear bumper
Solid mount roof rack and ladder
Stainless exhaust with new cats
Ashcroft lockers and transfer case
Hi flow air box intake
Two new coils with pitnium 3 plugs and 8mil wires
New o2 sensors all 4
MAF sensor replaced
Just recently put in new fuel injectors and upgraded to a hi pressure fuel pump
Purged out the carbon purge box thingy
I've been keeping her serviced and in good shape since I bought her in 2000 and started mod in 08
The gas milage has went from 18 hi way 15 town
And starting around 130k it started getting a consistent 10mpg
No mater the speed
Or tow/load
Off road lucky to get 8
I've thrown every thing I can thank of at her to help to no avail!
I know she is not a gas saver but I have hopes for better??
Codes have been thrown but I try to resolve them ASAP. Non at the moment.
Does any one have any input as to what I should expect ?
Any help is appreciate.
In addition just before posting this I had my oil changed and we found traces of petrol.
This is something new.
She is not missing, running great and still no codes??

Thanks!

 

Plugs dark, running rich? Coolant temp reasonable on a OBDII? Like not -40F? O2 readings changing, not steady.

 

Sorry not Realy following you there.

 

The ECU controls the fuel mix based on many sensor inputs. If coolant sensor is sending a lower signal than reality, like -40F, the ECU will dump more fuel because it thinks you need it. If the O2 sensors are not changing, something is wrong. Sensors that show up on a live data scanner should change. The truck will run with a sensor that is unplugged even, depending on the sensor.

So did the mpg drop happen before or after all the work you have done?

 

It actualy happened over a period of aprox 2k miles
Over about 6 months. The MAF sens whent and it got replaced, Bosch, not long I replaced the front bank 2 ( passages side ) o2 Bosch as well.
That's in the time I noticed an average of aprox 13-14 mpg
The lift and tires whent on, and it droped over roughly 4-5 tanks down to 9-10 mpg and that's where she sits. Since then all four o2s have been replaced (Bosch) as well as the coils plugs and wires. Like I seid, Iv been putting a lot of stuff in her, needed it any way but still?
I had read that the thermostat could couse problems? Do you thank it is sticking in the start up or open ( I thank or is it closed?) fuel cycle? I'm aware of most sinsors. Thought maybe for some reason it could be out of time a touch? Running maybe rich? I know they tend to do that a bit expecialy on cold start ups. Hince the fuel Oder in my oil today?
I appreciate the response to this it's just got me mystified !
Thanks

 

With a lift (less aerodynamic) and larger tires MPG will suffer.

The thermostat does not control closed loop operation, but it can delay it happening. The truck will drop out of closed loop on anything close to wide open throttle, so if you have to goose it to move with larger tires that could play a part. A scanner will show hen you are in closed loop.

Timing is set cylinder by cylinder on the fly constantly by the ECU. The knock sensors play a part.

 

Ok cool.
That is deffinetly going on. The moment I drove off with the lager tires it was considerable more to the floor to turn the wheels. I'm on to that. As for the knock sensor, I have a good understanding of its purpose and agree on the cylinder by cylinder.
I have anouther thermostat from a parts truck. Ill put it on to see if there is a diffeance just to see. Ill keep in mind the goosing it. But still mystified..
Thank you for all the input.

 

I don't think you'll see any mpg difference for coolant thermostat, but a 180F one will lower engine temps across the board. The engine coolant thermal sensor, top of the engine, is what tells the computer the engine temp. If it is telling a wrong value, like -40F (unplugged) or way below ambient temp when you crank up, the ECU might think you had relocated to Alberta and supply more gas. The value should show up on your scanner.