Not super duper urgent, but any ideas would help.
 
About 8 months ago I picked up a 93 3sgte from a forumer here (mrmr2), and have spent a fair bit of time swapping the engine from my 1990 mr2 (also a 3sgte).
 
I had a friend come around today and look at the wiring, and decided best to swap harnesses over from the 90 into the 93 engine.
It starts fine, it revs freely, but just doesn't want to sit on idle. Just drops and dies.
 
I changed the throttle body off the 90 onto the 93, and still the same problem.
 
Not entirely sure, but thinking it's a vaccum problem. Any tips? ideas? Anyone with the same problem?
 
There are no flashing lights to indicate a problem with the car, so no codes to be checked, as it has been done correctly but maybe the ECU from the 90-93 is different and has a different idle setting?
 
Cheers guys.
 

So let me get this right...
you bought a 93 MR2 with a Gen3 3SGTE, took it out and put your 90 3SGTE in it...

then swapped the harness out, put the 90 harness in with the 90 engine... and now it wont idle?

Yes, the 93 ECU is different.
The 89-92 (Gen2) use an air flow meter (stupid device!) between the air filter and turbo. the 93+ does not.
the pins are also different. there are three types.
89-90 (Gen2 rev.1)
91-92 (Gen2 rev.2)
93+ (Gen3)
 
The rev.1 dates may not be 100% correct, but that doesn't matter for you. You will need to change the ECU.
The 93 throttle body still would have worked i thought...
 
I've kind of done the opposite to you. I've got a patch harness running a 93+ ECU on my 92 engine. 

I guess what I wrote is a little confusing.
I own a 1990 mr2
the engine died so I bought the 3sgte out of a 93 mr2.
I put the 93 3sgte into the 1990 body with the 1990 harness.
 
So the AFM on the air filter might be causing it confusion? Would it be worth pulling that off for a start? or does it not work either way?

OK, double post, but It's a new update I guess.
 
I just went out and started her, and she did the same as last night, rough idle and dying without extra throttle.
I pulled the AFM off and started her, and she idled fine by herself. Very lumpy and rough, but she stayed alive fine for about 30-40 seconds before I turned her off.
 
Any ideas? remember - 93 engine, 90 loom+body (So ecu, airfilter intake etc is 90 as well.)

I doubt the AFM has much to do with it.
Sounds like a chronic vacuum leak to me - mine did the same when I installed a new intercooler with piping. One of the IC silicone bends/joiners did not fit correctly. Re-adjusted the piping and it ran properly.
EDIT: If its worse with the AFM installed than without most likely the above, as it'll be sensitive (lean) to unmetered air if its a vac leak somewhere between the AFM and TB.

Ok, So I took the throttle body off and checked the cold start injector resistance. The BGB says it should be between 2-4 ohms, but it was about 4.7. Would this have any effect?
 
Some other ideas are the exhaust pipe has been cut and tacked up just before the bend under the cat. Could this affect it?
The intercooler was swapped with one that I got with the engine, so maybe that has a leak in it somewhere? Pain in the ass if it does.
 
When I took the tb off, I double and triple checked all the piping to the intercooler when I put it on, and they are all good.
 
I do remember the seller (mrmr2, if you're reading) said there was a problem with the vacuum system. It may have been the little blue cylinder that was under the inlet manifold that was broken, which I replaced.
 
All the vac hoses are all on and none are split. Can't think of anything else that anyone might know.

The issue is your ECU.
here are the main differences.
Gen3 uses a different MAP sensor to the Gen2 because Gen3 DOES NOT use an AFM.
 Gen2 MAP sensor reads much lower than the Gen3 MAP sensor.
Gen3 ECU is tuned differently and is designed for a different flow rate in manifolds and turbo.
 
93 MAY still be a Gen2... if it came with the AFM, then it's a Gen2, and the differences are only in the pinouts.
If it didn't, then most of the information in this post is relevant.
 
Either way, you will need to either modify your existing harness
(google repin toyota harness)
or use a patch cable like the one below
http://www.berktechnology...-3sgte-ecu-patch-cable
 
 
the pinouts are different (seen below)
3SGTE pinouts.....
 
 
That should get you going a bit. the first thing to note is whether the 93 is a Gen3 or a Gen2. post a photo and it will be easy to identify. The valve covers are slightly different.
 
 

It's also worth noting that the American year models differ slightly to yours/Japans. 

Here's a (bad) picture I just took, hopefully it shows what you need.
As far as I know, the valve covers look the same between the 90 and 93 engines.

Thanks for the reply aswell : ) 

That pic shows a Gen2.
 
Cheers