KJ Fuel economy thread

[Auberon]

Given the last question:
Probably timely but respectful reminder as these are not scheduled maintenance but should be done anyway: ALL radically affect fuel trim.
and lots of people I note are new to diesels.

This is, of course, dependent on model as some have combined sensors (like the combined boost/intake air temp sensor); but each of the following require attention every second oil change (at least):
air filters;
MAF;
boost sensor also called MAP (Manifold Absolute Pressure).
fuel filter change every other oil change is important. It's an easy preventative maintenance step that many also try to run too long.

Condition of sensors is critical in regard to fuel trim.

ON ECONOMY numbers (manual calculation);
Our 2.8 KJ (2006 CRD) has been running to Mascot from outside the Windsor area regularly and is getting way better than that for economy - probably in the area of 10 l / 100km. Carries ARB bullbar, Warn winch and disability equipment all the time so its not light. Highway running is much better.

When doing this type of running only use BP from the same local garage.

All get regular attention. Other than that: currently no EGR tube (both ends capped) and Samco hoses fitted. The exhaust note is different - sweeter.

Due for oil change and sensor clean at end of month plus fuel filter change will watch with interest.

Hope that is useful.
Interesting point:
The oil stopped gunking immediately the EGR tube was blocked off so the valve can do as it likes - it is a closed system now - at the cooler anyway.

Will watch the new oil (Mobil 1) this time to see how quickly it "gunks" in the absence of exhaust gas. If oil lubricity degrades quickly with EGR pumping soot into it - the first minute if idle has an open EGR valve (I think) and wears a high tolerance motor how is that weighed against the miniscule gains in DIESEL NOx gains in the tiny amount reburned. VERY different to a petrol engine.

[MierMoto]

Update on the injector issue:

The plates, bolts and washers have been replaced on two of the injectors and it's running much better now. Obviously I've gained loads of power as it's now running on 4 cylinders and not just two and half.

It's still using more fuel than it should at about just under 12l/100km, but I think it's running too cold as was previously suggested. The gauge is sitting at less than quarter. I'm taking it to the Jeep dealership in Ballarat this weekend to have checked out anyway. They can plug it in and take a look at what's wrong so we can get everything sorted before it becomes a problem.

Cheers again for all the help. I'm really glad I popped onto this forum.

[bgbazz]

Good to see you have a result mate..anything is better than what you had before. The low temp thing is something to look at straight away as you realise. Mine was like that until I put in the new thermostat but now is as good as gold..needle sits just below half now and economy is low 8's. I got a Crown thermo from the Jeepy mob in the UK for about $100 delivered to Bulgaria, so you have an idea of cost compared to what you will be quoted there. There's a guy in Alice springs who is making/modifying them so you only have to replace the inner workings and not the whole unit as you do now, but I have no details on him.

Good luck.

[MierMoto]

Yeah, I'll probably just get them to list the issues and see what I can do myself and what I'd like them to fix. Hopefully they're all straight forward fixes.

[bgbazz]

If it turns out to be just the thermo, you can do that yourself quite easily. No special tools required and not a lot of dismantling to be done..I did mine in about an hour or so.

[KJ_andy]

Originally Posted by adamdebenham

My 03 Cherokee uses so much fuel. I'm considering an LPG conversion. But are there ways of getting better fuel economy? It's we worse when towing a box trailer, which surprised me? Love to hear how others are conquering this? I'm new to the forum, so love to hear? Adam

Hi, First read through this thread and see if any previously raised issues can solve your setup. Check tyre size, are you running standard size? As this can alter the EVIC reading and economy, don't believe the EVIC first up. Do the math with fuel in/km driven. Saying that the petrol is a thirsty V6, especially on short trips and around town. Once warmed up she gets better.
I added a Jet Power chip from JeepinByAl (JBA ). It was plug and play, instructions in pack. It has improved economy but I have a winch bar (extra weight), a lift (extra drag) and tyre size change (alters torque/rev band), these all add to less than perfect fuel economy but give offroad capability - your choice really. The chip alters the transmission change points and improves economy especially when towing.
Try running a higher octane rated fuel for a couple of tanks (it can clean up the injectors). I'm wondering about oxy sensors myself as I have the same age motor and it has generally got worse with age; as well as mods. Running about 15L/100kms at the moment. Started new at 13.6.

[Sappa]

Ok, I have some figures to add.

Driving fast on highway (about 110km/h): 10.5L per 100km.
Driving on highway at 100 km/h: 9L per 100km.
Driving on a 4x4 track: 10L per 100km.
City driving: 10L per 100km, sometime i get 9.3L.

All figures where using a full tank to empty on a single trip. Note that my tyres have been up sized from stock so my trip computer is a little out, but if anything that gives better results.

My Cherokee is a 2006 CRD.
Manual gearbox
CRDStu lift
ARB bullbar
245/70/16 BF Goodrich AT