well, i brought in a number of LJ78/71 vehicles over the years. all in very clean, well maintained shape. all stock.
the LJ78 was noted as a poor fuel mileage beast (for the engine size) with average highway fuel consumption of 21-26 mpg. i had one that was returning 28 on a run to Edmonton and back on the back roads.
the LJ71 did slightly better with an average between 24 and 28 mpg, depending on speed, wind, land configuration. i had one that returned 32 mpg on a similar trip up to edmonton and back on back roads.
the gearing is brutal with these trucks. i suspect that a set of 4.11s would have been almost perfect and regulating your personal top speed to 100 k/h.
in the city, which the OP originally inquired about, the LJ78/LJ71 sucks fuel ... literally. heavy truck, low gears, small engine and usually a heavy foot trying to get up to speed from a dead stop.
there are two things i dislike about the LJ series, head design (and buddy, if you think the 3L head transplant solved your problems you are sadly mistaken) and fuel mileage. there is nothing you can do about the head design, they will crack ... where and when is the gamble. fuel mileage can be modified by driving style. easy acceleration, steady speeds, keeping the top speed to 90 (4.88s) all help somewhat. but. it is a small engine trying to move a vehicle that isn't that much lighter than a 80 series. 1930 kg - LJ78 // 2100 kg - HZJ81
other than these two issues i really enjoyed my 2 personal LJ78 and single LJ71 that i built up for DD/off road vehicles.
one change i did make that "seemed" to help was the installation of 33" skinnies. you can run 33 skinny tires on a stock 71/78 and it seemed to lower the rpm and yet coupled with the 4.88 gearing the engine moved the truck nicely. once again slow steady acceleration makes the difference.
Hey crushers, thanks for your experience and thoughts. I think the fuel economy you saw with the LJ7x's is pretty typical across the board from what I've read now. There is one guy on this forum who got exceptionally good fuel economy. I don't know what was different about his rig, but it is my goal to attempt to achieve the mileage he was getting. Here are a couple of quotes from his posts on the subject a few years ago (his LJ was stolen after this):
prado t said:
I get 21-25 mpg in city and hwy in o.d. at 100km/h at 2450 rpm it gets 33-37mpg
aaron kuit
prado t said:
Hi My LJ78 combined city and highway would average 27-28 mpg. It was an automatic any city driving was during rush hour stop and go in Vancouver. On the highway it did very well at 100- 110km/h wich is 60-67 miles per hour I could get mid 30 s. I had an OME 2.5" heavy lift ,heavy front for the factory AISIN winch so the front would not sag and ARB rear locker.
One thing I recently read that has made a big difference for some LJ78 owners fuel economy (as RADD recommended earlier in the thread), is replacing the in block ECU temperature sensor. That is one of the next things on my list, and I'll report any effect it has on my economy. Turns out the temp sensor part number is shared across many Toyota engines, so I should be able to get one at my local Toyota stealership.
I agree the 4.88 diffs are not the best for economy, but they are nice off road. I put on 235/80/R16's (32's) to offset them a bit. My rpm's sit in a sweet spot on the highway in my opinion. Any lower and the truck would be too low out of the power band. I run my tires at 50psi now in town and on the highway as they are E rated and good to 80psi. So my truck has pretty low rolling resistance.
I know that the 2lte is prone to head failure, but I got my truck cheap ($3500), so was willing to take the risk. If I could have afforded an HZJ7x, or PZJ7x, I would have bought one, but I'd be looking at probably $20,000 more than I bought my LJ78 for. And really, I love my LJ78 for my needs. Other than the engine, the HZJ7x and PZJ7x doesn't have much to offer me (I prefer coils, and I like that my LJ is lighter weight with more seating and comfort). 8" rear diff is fine for me. As you've noted in the past crushers, the LJ's are very capable 4x4s too. I got it cheap because the previous owner thought he had wrecked the engine (it was belching massive amounts of blue smoke when I bought it). Turned out he had kinked the PCV hose to a custom catch can he had, and the engine was just building high crank case pressure and pushing oil into the combustion chamber. I fixed it within 30min of getting it home.
He had just spent a crap load of money trying to fix the problem, so I ended up with a fresh rebuilt turbo, and rebuilt injectors on the truck as a bonus.
I don't think I could justify paying the full $7-8k these things seem to be fetching in 'good condition' though. That is too much money with the risk of the head going at some point. I would rather buy a 1996-2002 four runner (essentially the next generation Prado) instead for that price.
With regard to the head's on these things, mine has been in Canada for 50,000kms and 6 years. It still has the original head (so no 3l head on mine as you assumed crushers). The first owner had the cooling system serviced right away, the second owner was ignorant about the head issues, and beat the s*** out of the truck but got lucky and never cracked the head. The cooling system on mine works A-1, and even on the hottest day and biggest hill, does not have any problems cooling the engine. So I think this is what has saved it despite lack of maintenance building up in other areas.
I personally think these engines can be made reliable with the right maintenance, modifications and driving style. Why? Because the normally aspirated L series reportedly last 400-500 thousand kms with no head issues. So the difference in the equation for the 2lte is the turbocharger. Added heat and pressure exasperates any issues with the engine, and ends in a damaged head. The 2lte engines run their first 100,000kms with no head cracking (which proves it's possible to run them with no cracking), but as the lack of maintenance adds up....bang, they crack.
The 2lte being one of Toyota's first electronic diesel engines, with emissions control, means that as the engine cokes up and sensors fail, the engine becomes vulnerable to major problems. Of all the turbo diesel engines Toyota has produced, the 2lte and 1kzte run the highest compression ratios, which does nothing to help the engines either. The EFI failure mode in almost all cases is an engine that is constantly over fueling, and thus running way too hot.
Basically, I think the head cracking is due more to a perfect storm of smaller issues than the weakness of the head it's self. It's just that as the smaller issues add up, the head is the weakest point in the system and the first thing to go. Toyota set up this engine to operate too close to the edge, with no safety margin in the tuning or application.
The issues with the 2lte as I see it are:
- EGR system creates major problems by sludging up the intake manifold and intake ports thus reducing the amount of air getting into the engine. The computer doesn't know this, as it doesn't measure the air going into the engine (like a gasoline engine), but only looks at the TPS and boost sensor and adds fuel according to tables in the ECU. A clogged manifold if anything will run higher boost, as the air cannot get into the engine as efficiently. The computer adds even more fuel as the boost goes up. As the fuel goes up and the air is reduced, the EGTs climb quickly, thus adding more heat and stress to the engine.
- The EGR system adds hot gasses to the intake, which does nothing to help EGTs.
- The EGR system needs the throttle butterfly's to work (create vacuum and suck in exhaust gasses). The throttle butterfly's limit the air the engine can get at low throttle positions, and the small throttle is prone to malfunction as it clogs up from the PCV crap and vacuum leaks or VSV failure. This again raises EGTs, and causes other issues like hard starting etc.
- The PCV mixes oil droplets to the EGR carbon to create a sticky gummy mess in the intake.
- Running sludged up and with improper injection volume leads to carbon build up in the cylinders which increases the compression ratio which does nothing to help the situation.
- Lack of cooling system maintenance (clogged radiators, tired thermostats, clutch fans not working, rotten rad hoses, air lock in head) means the system cannot dump the extra heat created by the above problems.
- Injection pump and injectors getting dirty and injecting incorrect volumes of fuel. Caused in part by owners not running diesel fuel additives which keep the system clean and reduce friction in the moving parts.
- The ECU's have capacitors that can fail, causing any combination of issues that can result in improper diesel injection timing/volume and increased EGTs.
- The in block temperature sensors can begin to fail, and in many cases it seems end up telling the ECU that the engine is cooler than it really is, thus causing more fuel to be injected than is needed. Again resulting in raised EGT's
- A small engine in a large vehicle has to constantly work hard, so is at a disadvantage even in the best of condition never mind when the EFI system is not working properly. Not only that, but a lack of intercooler and a restrictive exhaust system also add to the problems.
- And this list goes on. So basically, sludged intake + failing EFI + failing cooling system + small engine with big load + high demand of Canadian driving = high EGTs + over heated coolant = cracked head. Makes complete sense to me; something has got to give.
I think all these issues can be rectified to create a reliable engine. Clean out the sludge, clean out the carbon, remove the emissions systems, remove the throttle plates, service the EFI system (repair the ECU, replace out of spec sensors), service the cooling system back to 100% capacity, run a decent diesel additive, add some sort of tuning, and drive within the capabilities of the engine (a pyrometer is a must).
And more power and performance can be had with larger downpipe/exhaust, a large capacity intercooler, increased boost, and fuel tuning capability. Some have claimed 40% more power on the dyno over factory ratings with these sorts of modifications. Which is pretty decent power for such a small engine (135hp, 245ft/lb at the flywheel?). A guy here (post #583) upgraded the turbo on a 2lt II and is claiming 150hp 229ft/lb
https://forum.ih8mud.com/70-series-tech/31716-post-pics-your-modded-7x-series-30.html ! I don't know if that is flywheel power or wheel power...
Wow, I typed too much there. Just had to get my thoughts on the 2lte out, haha!
I actually don't mind the engine to tell the truth. I'm happy with the power mine puts out, I like how smooth and quiet it is, and I like how it revs. I'm just going to work on making it as reliable and economical as possible, with a couple more power mods.
