This week I just completed my third 12 hour interstate endurance trip. Each resulting in an oil change when I get back home. On this last trip, I have noticed that each trip seems to produce a lower and lower MPG even though the average speed (68 mph) has stayed the same for these trips. My second observation is while the cruise control is engaged, the car will down shift to 5th or even 4th depending upon how steep the hill is, but will not shift back up to 6th only to 5th unless it is going down hill. I do not have this problem if I am not in cruse control. I apply though throttle, it will down shift later than if in cruise control and will up shift to 6th when I am at the top of the hill. I think my MPG is low because I did not notice that the car spends a lot of time in 5th gear at 70 mph. I can move the shifter over and manually shift up to 6th and then put it back in normal mode, but the next hill will cause the same issue of not up shifting when I reach the top. This issue seems to only be a problem at 70 mph and above.

My wife suggested (and of course I will follow her advice) was to remove all of the "crap you have bolted on that thing" and see if the problem goes away. I will admit that the number of bolt on items has increase over time, but I did not think it would affect the transmission at highway speeds. mpg yes, up shifting, no)

So after a lengthy consultation with my wise and wonderful household land rover technician (my wife), I my list of things to try.

1. Remove all of the "crap bolted on", remove the winch on the front bumper, remove the 4 big aux lights up top, remove roof rack, remove the fridge from the back cargo area, removed all the recovery gear behind the middle row seats, remove the camping gear, remove the radio antennas, and even remove the floor mats and the two half empty water bottles in the console fridge.
2. Do a fluid change through the radiator hose connection.
3. Reset adaptive learning for transmission and engine.
4. Tranny flush from the local BG product shop.
5. Pull the pan, change out the solenoids, put in new filter and new fluid and any other preventive measures that may be required (wire loom seal?).
6. Take it the local Indy shop and say "FIX IT".

and as a last resort, beak down and buy a new 110 defender (with a warranty)

Is there anything you would add, or rearrange? (except moving purchasing the defender to the top of the list)

I look forward to your thoughts.

Jeff

 

Shifting behavior actually has A LOT more to do with engine inputs than anything else. For example, transmission behavior is heavily influenced by MAF sensor readings. So before you focus 100% on the trans, make sure you do a run down of engine items like spark plugs, MAF, PCV, EGR, throttle body cleaning, etc, etc.. I would even say to try engine adaptations reset first since doing a trans reset is only recommended after servicing and not ideal as routine troubleshooting.

When it comes to the trans itself, certainly consider fluid if old. Solenoids can be observed with GAP tool, including torque converter lock-up. If the TC is not locking, thats generally a sign that something is up. And the TC lock is when you get your best economy.

 

I thought engine control and even something as simple as all that stuff hanging on the out side is creating enough drag that the engine is telling the transmission to down shift to get the RPM in a range to get the power needed. Plugs are only 29,000 mile old, So your list would be clean/replace MAF, PCV (which I do every 30,000 and is due in 1,200 miles) during my last fuel stop, I heard that classic metal sloshing noise that seems to be at a different speed than the engine, so looks like I will be replacing the water pump while I have the throttle body off for cleaning. Most of the engine things can be done this week. The EGR will wait until next weekend.

Thanks for the advice I will report back what I find, and especially thanks for not putting the Defender at the top of the list

Jeff

 

Roof rack and its bolt ons make a big difference, luckily with the TDV6 the added weight makes little difference to the economy. Since fitting a Llams suspension controller i can lower the car at highway speeds for a little less brick affect.

 

I made several changes without testing each one before making the next change so I will have to guess as to what almost fixed it-------Sorry.

So far I have:
1. Cleaned MAF- My log book shows I did that about 27,000 miles ago- Don't know how dirty it was.
2. Cleaned throttle body- My log book shows I did that about 27,000 miles ago- It was not very dirty and wiped up rather easily.
3. Changed Air Filter- My logbook shows I made a mid service change about 12,000 miles ago- It was dirty.
4. Did a gearbox fluid exchange using the radiator hose method then service manual method to top off (drain out?) to get the level correct. - First logbook entry for this service.

My 65mph cruise mpg went to 16.8. My 70+ mph went to 16.2. So, I may (or may not) have found the problem. Also noticed that it was ever so slight more likely to upshift to 6th at the top of a hill or just past the top, so I may be heading in the right direction.

My plan moving forward:
5. When it arrives, I will do a mid service PCV change. (I do that every 30,000 and it will only be 3,000 early.
6. Follow my wifes' advice and "unbolt all that crap" (I need to move the table under the rack and re-run some wiring anyway).
7. Do a Diff and transfer case fluid change which is due at 140,000 and considering I have been swimming a little bit at the beach, I may do them early.
- and last but not least I was told to "CHECK THE TIRE PRESSURES"

I will update as I do more, but I am heading in the right direction.

Jeff

 

Well now it seems to like shifting into 6th a "little" sooner in cruise control, but not much sooner. Now I notice that the mpg is around 9.2 average. Highway gets me to 13.7 but goes back down the minute I exit onto city streets.
I changed the engine air filter, cleaned the MAF, cleaned the throttle body, changed the oil, changed the PCV (it had 30,000 miles so it was due anyway) Fuel trends look good

Bank 1 short term0% long term -3.13
Bank 2 short term 0% long term -3.19%

so now I am thinking of a can of sea foam injector cleaner and an adaptive reset, but these fuel numbers look good to me.

I am at a loss as to where to go from here.

Jeff

 

Your short trims stay at 0?

Either way, can probably rule out fuel pump. I just resolved a low pressure issue and my long term trims would hit 19 and average around 10 to 14. So you are not running lean. Seafoam would not hurt, can do it induction style too.

What are the age of the O2 sensors are were they Denso or Walker or some other brand?

 

Don't know the age of the O2 sensors, probably original so 140,000 miles and 156 years. That could be an option if the fuel trim was out of line, but they are OK. But I will put it on the list

 

But trim readings come from O2s, so my only thought is they are not efficient but not bad enough to trip a CE. Generally they get replaced every 100k miles. The question is if they have been done or not before. I did mine not knowing at 105k miles, when I bough my LR3.

On a side note, with roof rack and two traction board poorly paced on it I managed 19.3mpg today on a 150 mile trip in Door County, which is like Marthas Vineyard for Chicago people. So 55mph max and lots of little towns to slow down in. Stopped at lots of places too. I was not frisky, but I was not trying for best economy either. Average exterior temp was about 72-75F.