Thinking of buying a MK4 Supra… anyone got advice?

Hey everyone, new here. I went to check out a 1994 automatic Supra today, and I’m considering buying it. The car’s interior and exterior are pretty rough, but mechanically it seems solid (based on the test drive). The price is quite tempting, but the guy selling it swapped out the stock ECU for a Haltech one. Now, the car only shifts into 1st and 2nd gear, and when trying to shift into 3rd, it just goes into neutral. Shifting between 1st and 2nd is smooth, though. The seller thinks it’s a tuning issue that could be fixed by just connecting a laptop to it. Has anyone here dealt with something like this before? Should I just go for a manual swap? I’m not too sure what’s the best move.

UPDATE - Thanks for the input, everyone. Unfortunately, I found out the car was marked as a repairable write-off in 2005. That’s kinda put me off, especially with the price the seller is asking. But I’m still open to hearing suggestions if this could still be a good deal if I negotiate a lower price. Appreciate any thoughts!

Just grab an automatic ECU, they’re not that expensive. But yeah, if you’re considering long-term, the manual swap is a good idea. It’s not too hard to do and won’t break the bank if you go with an R154.

@Mitchelle
If I go for the manual swap, this would be the first manual car I’ve driven. I was thinking of keeping it automatic for now and getting it running smoothly before switching. How difficult is it to swap the ECU?

@ReubenSparks
If the previous owner didn’t mess with the wiring harness, it should be a straightforward swap. The ECU is usually located behind the glovebox on the passenger side.

Mitchelle said:
@ReubenSparks
If the previous owner didn’t mess with the wiring harness, it should be a straightforward swap. The ECU is usually located behind the glovebox on the passenger side.

Yeah, he showed me the ECU and everything’s still on the passenger side, though the wires are all over the place. What ECU would you recommend I switch to? Or should I try tuning the current one to get it working?

@ReubenSparks
It depends on what you’re aiming for. Haltech ECUs are great but need tuning. I’d recommend finding a local tuner who knows Haltech well. If you’re not chasing crazy power, a stock ECU would be more convenient, though they do develop capacitor issues over time.

@Mitchelle
What do I do if he’s already modified the wiring harness? Do I just have to work with the current Haltech ECU?

Mitchelle said:
@ReubenSparks
If the previous owner didn’t mess with the wiring harness, it should be a straightforward swap. The ECU is usually located behind the glovebox on the passenger side.

Yeah, he modified the wiring harness. It’s all plugged and pinned from the factory ECU to the Haltech one.

Your best option might be to have a tuner take a look. Is it twin-turbo?

graceruth said:
Your best option might be to have a tuner take a look. Is it twin-turbo?

No, it’s just the standard setup… whatever that’s called.

ReubenSparks said:

graceruth said:
Your best option might be to have a tuner take a look. Is it twin-turbo?

No, it’s just the standard setup… whatever that’s called.

How much are we talking? Be ready to pay a lot for interior panels or trim pieces. I saw a dashboard on eBay for $3000, no joke.

@graceruth
The seller’s asking for 17.5k AUD. I’m prepared to invest quite a bit into this car though.

ReubenSparks said:
@graceruth
The seller’s asking for 17.5k AUD. I’m prepared to invest quite a bit into this car though.

Sounds like you’re ready! Go for it.

@graceruth
You can still get OEM dashboards from Toyota dealers at a decent price. I bought one just a few months back.

Monty said:
@graceruth
You can still get OEM dashboards from Toyota dealers at a decent price. I bought one just a few months back.

Are you sure? I thought they sold out of the LHD dashboards over 10 years ago. Parts for this car are tough to find. Try sourcing a V160 part, or even a differential. The good news is you can repair dashes, and adapters exist for different transmissions.

@fortuna
Yeah, I got mine from Elmhurst Toyota: https://parts.elmhursttoyota.com/oem-parts/toyota-genuine-toyota-1993-1998-supra-mk4-instrument-panel-dash-pad-board-5540114510c0. Any Toyota dealer should be able to source one for a similar price. But I do agree, a lot of stuff has been discontinued, and it’s a pain. Check out Junsei, they’re making high-quality replacement parts for the MKIV: https://www.junseiautoparts.com.

@Monty
I’ve bought from Elmhurst before too, but just because they list something doesn’t mean Toyota will actually sell it. Also, avoid their “Toyota” brake pads—they’re terrible.

If it’s a Haltech running on NSP, it’s just two solenoids in the transmission that are controlled by the ECU. I don’t see anything in the ECU that would cause the car to go from 3rd to neutral. This sounds like a mechanical issue to me unless it’s a Haltech Platinum, which I’m less familiar with.

@Monty
It’s running a Haltech Elite 2500, plug and pin setup. Someone in another group mentioned that this ECU can control auto gearboxes, so I think it just needs proper tuning, which the previous owner didn’t have time for. If it’s the solenoids, that’s not too expensive to fix here.

@ReubenSparks
I’ve got an Elite 2500 controlling an A340e. It’s just a dropdown in the software—there’s no tuning involved that would cause your issue. You can set shift points, but that wouldn’t make it go into neutral.