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Discussion Starter · #1 ·
Did a 2jzge swap [donor car was a 1994 SC300 with an Auto transmission] in to my 1985 Celica Supra with a 5spd transmission, plan on doing a write up on that experience later.

My issue is while driving, the car won't go past 4,000 rpms.

From what I understand I need to get 12 volts from the STA wire to Pin 77 and 76 during crank... I'm only getting like 10.46 volts during crank

made my connection to the STA wire in the steering column

Is there a better place for this connection so I can get 12 volts during crank?

[pics for reference below]

Steering column STA connection
Motor vehicle Bumper Automotive lighting Hood Electrical wiring


STA jumper, Pin 77 & 76 (tied together for testing)
Circuit component Electrical wiring Electricity Gas Motor vehicle

Circuit component Electrical wiring Audio equipment Computer hardware Cable


10.46 volts
Vehicle Motor vehicle Audio equipment Gauge Measuring instrument
 

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With these cars being so old that voltage to me is a good circuit. There is no starter relay that handles the current, the switch itself handles the current, so I would assume contacts are just worn.

I have my car wired the same exact way. 2jzge 93-97 gs300 harness and auto ECU. 85 P type. Never had a problem with a 4k redline.

Have you tried running it with STA and NSW just not connected? My swap originally didn't hook these up and the car still ran fine without them.

Also do you have any check engine codes?

If you haven't you might want to skim this thread (1) 2JZ-GE PnP wiring guide | Toyota Celica Supra Forum

I went through a lot of bugs with my GE swap and ironed a lot of them out in the later part of that thread including STA, NSW, and the MREL for the ISCV as that is pretty specific
 
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Discussion Starter · #3 ·
Thanks for the response!

I have have been running it with STA and NSW (pin 77 & 76) connected and grounded to the chassis for the last year, then I got that itch to "fix it" so I can go past 4,000rpm under load/driving.

there were no check engine codes originally, when I connected the STA wire to pin 77 & 76 I get rapid flashing, I looked that up and it means no issues.

I suppose, I will be checking connectors and wired connections this week
 

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Which ECU are you using? Manual or auto? The states of these two lines vary depending upon ECU.

Does low-voltage when cranking cause you problems with going over 4000-rpms later? Where are you getting this info? Connect external diagnostic tach to verify dash tach is reading accurately.

Due to voltage-drop during cranking, you're not gonna get above that 10.46v you've measured. Way around that is to store up higher-voltage BEFORE cranking. Then feed it back to that line while it's cranking. Can be done with capacitor, diode and current-limiting resistor.

STA connects to starter circuit, so should only have +12v when cranking, otherwise it's grounded.
NSW should have +12v only when cranking. Then grounded after ignition released from START position.
STA & NSW should NOT be attached to power OR ground. They should be connected to relay that feeds it +12v when cranking, and grounds it all other times.

BTW, how is any voltage even possible on that STA-NSW connection if you've got it grounded? Would be blowing fuses or frying ECU.
 

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Mk2 chassis doesn't have a starter relay. Starter wire goes straight from the ignition switch to the starter solenoid on manual transmission chassis. Branches somewhere in the harness to feed starter signal to STA on the 5mge ECU.

STA will show ground at rest on a meter just because of the starter solenoid coil. So it will show ground and then during crank will go to 12v and back to ground after letting off the starter.

The oem 5m ecu takes STA in as well. There is a STA pin on the ecu body connector behind the glove box, no reason to run a wire to the ignition switch. Black wire in the same plug that has the yellow/green temp sender wire

I've seen other people have a soft rev from STA NSW not being hooked up but I never had an issue there.

Per wilbo GE wiring pinouts

NSW
Automatic transmission: This pin is connected to Ground by the Starter Relay coil via the automatic shifter position switch when the automatic transmission shifter is in the 'N' or 'P' positions.

Manual Transmission: This pin is connected to the engine ECU STA pin inside the engine wiring loom and hence is connected to battery voltage when the ignition switch is in the CRANK position. When the engine is not being cranked this pin is connected to Ground via the Starter Relay coil

STA
Automatic transmission: This pin is connected to battery voltage when the ignition switch is in the CRANK position and the automatic transmission shifter is in the 'N' or 'P' positions. When the engine is not being cranked this pin is connected to Ground via the Starter Relay coil.

Manual transmission: This pin is connected to battery voltage when the ignition switch is in the CRANK position. When the engine is not being cranked this pin is connected to Ground via the Starter Relay coil.

You've effectively done this just by hooking those two wires to the starter wire at the column. 12V during crank and ground at rest due to solenoid coil. If it is an Auto ECU you could try connecting STA like normal and then ground NSW, but there again I never had an issue here with NSW or a soft rev.

I don't particularly think the soft rev is from STA or NSW, Keep in mind NSW does different things depending on the ECU. My auto trans is wired per how a manual transmission ecu works (bold print^) and runs just fine. I've also ran STA and NSW just not connected at all when I first did my swap and it made no difference. I would keep STA how it is and maybe mess with NSW and then go check for other things. Typically with throttle stuff I usually go towards the TPS but with no codes you're just going to have to test sensors per the TRSM
 

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Discussion Starter · #7 ·
I'm using the auto ECU that came with the engine

when the swap was originally done nothing was done with the STA or NSW, they were connected together and grounded because it made the car run better. Car has always had the 4,000rpm limit when driving. When parked and not in gear the car will rev all the way up to 7,000rpm with no issues.

I searched various toyota, celica, supra and lexus sites seeing what other folks who had this issue (2jz in limp mode, not reving past 4,000rpm etc..) were doing to fix it.
Most common answers were:
1. buy a standalone ecu
2. power the pin 77 with a STA source (for an auto ecu) leave pin 76 untouched or connect it to the STA source too...
3. use a manual 2jzge ecu (I'm assuming its not as picky as an auto ecu)
4. replace/rebuild ecu
 

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If it revs to redline not under load but won't go past 4000 while driving I don't think your issue is with either of those wires. I would think the problem would be there regardless of idling or out driving if it was STA or NSW
 
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