New-to-me LJ78

[tdbeasley]

Hey there!

Just purchased a 1990 LJ78 with the 2LTE. These forums have been tremendously helpful for figuring out if I wanted to buy this thing and what ownership may look like. So, thank you! My background is in Datsun stuff so it’s neat to see how builds take shape on the Toyota side of things.

So far the truck has been a treat to drive. I purchased it on Vancouver Island and I’m told it was first owned by a lady in Comox who had it serviced regularly in Ladysmith. I believe at Flying Pistons. I’ve called them to ask for some service records as I’m not yet sure what head it’s got on it. It’s at 308000 km so I’d assume the head has been done at some point.

Previous owner looked after it and didn’t put much mileage on. Came with some service records, new turbo, rebuilt rad and an EGR delete.

First on the docket:
- I’ve noticed the OD light flashing so I’m going to pull the ECU behind the glove box and see if the capacitors are in good shape. Maybe replace them with high quality digi key items.
- I read that this could maybe be caused by a speedometer sensor (Speedo is also reading 20km/h higher even with 32 series tires) would that be part number 83181-20040 ?
- oil change
- air filter change
- pyro sensor and gauge (on order)
- water temp guage
- rear sway bar link rs

Next on the docket
- water to air intercooler
- boost gauge and sensor
- manual boost controller
- tend to a little rust
- minor aesthetic tweaks
- front seat upholstery to match rears

Further regarding that flashing OD issue, it seems like it’s sometimes starting from a dead stop with OD engaged in first gear until switched off or shifted into L and truck drives totally normally. On the highway I noticed the OD pulsing on and off occasionally. Any tips with this?

Goals with this truck are to do some slow steady road trips and light wheeling. I’ve read to keep these things under 3k, maintain them well and keep them cool and hopefully they treat you nicely in return.

Thanks very much! Looking forward to more! If you recognize the truck lemme know

 

[OGBeno]

Welcome. Enjoy your truck. Tons of information in this section and in the diesel section regarding your engine. Read up!!

 

[AirheadNut]

Welcome! Regarding the speedometer, the LJ78 uses a cable driven mechanical speedometer, so there is no "sensor" per se and no feedback to the ECU. Is the speedometer needle steady or does it bounce? That could be an indication of a cable that is wearing out.

Your first check with a flashing OD light should be to check the diagnostic codes using the port in the engine bay (don't remember the specifics, there are threads here that go into detail). That should narrow down what systems to check.

Strange shifting behavior could be failing caps in the ECU or failing shift solenoids in the transmission. In my first LJ78 I had problems with the torque converter randomly shifting out of lockup once the transmission fluid was up to temp, swapping out the shift solenoids solved that problem. The engine coolant temperature sensor located under the intake manifold can also cause odd transmission behavior when it fails.

 

[tdbeasley]

Thanks for that and duly noted! Needle isn’t super bouncy.

I’ll track down an OBD reader and look into that.

I’ve searched a bit to no avail but are there shop manuals for these trucks that shows exploded parts diagrams and codes and what not?

Am I correct in thinking worn solenoids may cause a delay even when shifting manually between gears? So far trans shifts smoothly and instantly when shifted manually. I’ll check that probe too.

Cheers!

 

[AirheadNut]

In my case the only shifting issue I had was the torque converter lockup, it always shifted fine otherwise. There are shop manuals available but they don't have part diagrams with part numbers. You can find those at places like megazip.net and partsouq.com, use your frame number to look up the parts diagrams. FSM's (factory service manuals) can be found under the Resources tab here. The diagnostic port doesn't use a typical OBD reader, as I recall they require a jumper to activate either the glow plug light or OD light. The flashing pattern will relate to a diagnostic code.

 

[AirheadNut]

Here's some more info about the diagnostic process:
Toyota 2LTE error codes - https://forum.ih8mud.com/threads/toyota-2lte-error-codes.201623/

M

Thread 'OBD1 Code List for '91 Prado 2LTE'

Mar 25, 2018

Does anybody out there in radio land have/mind posting the error code (OBD code) list for my 91 Prado?? The only lists I have found on mud or elsewhere are only for different models but the same engine(2LTE). I get a code 28 and would dearly love to know what that means. Unless its code 2 and 8 but i have a hard time imagining the turbo pressure sensor and air temp sensor failing at the same time. Thank guys!

• masface
• Replies: 8
• Forum: 70-Series Tech

 

[tdbeasley]

In my case the only shifting issue I had was the torque converter lockup, it always shifted fine otherwise. There are shop manuals available but they don't have part diagrams with part numbers. You can find those at places like megazip.net and partsouq.com, use your frame number to look up the parts diagrams. FSM's (factory service manuals) can be found under the Resources tab here. The diagnostic port doesn't use a typical OBD reader, as I recall they require a jumper to activate either the glow plug light or OD light. The flashing pattern will relate to a diagnostic code.

Wooooow! Thanks for all that info! Really appreciate it. I’ll check out those sites and tab.

Sweet I don’t have to get that obd! Makes the threads I was reading about the process make a lot more sense haha

This is the newest car I’ve owned so the idea of a car telling me about its problems, even in a limited capacity, is very novel haha

 

[Reedys]

Welcome! Regarding the speedometer, the LJ78 uses a cable driven mechanical speedometer, so there is no "sensor" per se and no feedback to the ECU. Is the speedometer needle steady or does it bounce? That could be an indication of a cable that is wearing out.

Your first check with a flashing OD light should be to check the diagnostic codes using the port in the engine bay (don't remember the specifics, there are threads here that go into detail). That should narrow down what systems to check.

Strange shifting behavior could be failing caps in the ECU or failing shift solenoids in the transmission. In my first LJ78 I had problems with the torque converter randomly shifting out of lockup once the transmission fluid was up to temp, swapping out the shift solenoids solved that problem. The engine coolant temperature sensor located under the intake manifold can also cause odd transmission behavior when it fails.

Interesting, I noticed mine slightly bounce today around 70km/h and then next time I started the car (I stopped to grab something at the shops) it was back to being suuuuuper sluggish. I wonder if this has been my issue all along with my 'limp mode'?

 

[AirheadNut]

I doubt the speedometer would have anything to do with transmission or engine limp mode problems, as far as I know the speedometer and it's drive system is purely mechanical and doesn't feed information to the ECU.

 

[Reedys]

I doubt the speedometer would have anything to do with transmission or engine limp mode problems, as far as I know the speedometer and it's drive system is purely mechanical and doesn't feed information to the ECU.

Okay perfect, thank you!!

 

[tdbeasley]

Interesting, I noticed mine slightly bounce today around 70km/h and then next time I started the car (I stopped to grab something at the shops) it was back to being suuuuuper sluggish. I wonder if this has been my issue all along with my 'limp mode'?

I’m almost certain this is shift solenoid related on my truck. Until it’s hot, it doesn’t like going into 1st at a stop and will sometimes start in 2nd sometimes 3rd. If you didn’t know any different and stepped on it without shifting into 1st manually, it would just roll coal and barely move… likewise it’ll pop out of lockout on the highway unless coaxed back in using od on off.

I’m in the middle of rebuilding the knuckles but solenoids is the next thing waiting to be done. PO used rtv for the pan (more time needed for removal) and used low viscosity Canadian tire brand ATF so I’m going a flush to Dex III while I’m at it. I have wondered if the low viscosity atf may have some bearing on these issues. Hoping that once the solenoids are replaced the OD stops flashing. Didn’t get any codes when I ran them…

More soon!

 

[tdbeasley]

Okay perfect, thank you!!

Any luck sorting out the “limp mode” condition you were experiencing?

Today I changed the 1st gear solenoid and flushed and changed ATF to a Dex III compatible Velvoline. The truck shifts perfectly. Starts in 1st gear from a stop and doesn’t pop out of lockup on the highway. No flashing OD light either.

 

[EngineBlockEggs]

I doubt the speedometer would have anything to do with transmission or engine limp mode problems, as far as I know the speedometer and it's drive system is purely mechanical and doesn't feed information to the ECU.

When my speedometer cable broke on my old LJ78 the engine would no longer go above 1000 rpm. If my memory serves me correctly it was basically stuck in first gear.

 

[AirheadNut]

When my speedometer cable broke on my old LJ78 the engine would no longer go above 1000 rpm. If my memory serves me correctly it was basically stuck in first gear.

That's really interesting! Turns out there is a speed sensor output that goes from the combination meter to the ECU, I thought it was just for the speed alarm that comes on at 110km/h in JDM models but it must correspond to limp mode when the speedometer isn't registering.

 

[EngineBlockEggs]

That's really interesting! Turns out there is a speed sensor output that goes from the combination meter to the ECU, I thought it was just for the speed alarm that comes on at 110km/h in JDM models but it must correspond to limp mode when the speedometer isn't registering.
View attachment 4163428

Yeah, it was surprising to learn how much the truck relied on the speedo cable, lol. Like you, I never would have guessed.