20 valve Blacktop ECU Grounding Points

[hayashi]

Car: AE86
Engine: 20 valve blacktop 4AGE

20 valve blacktop engine exhibits extrodinarily high idle at 2000rpm. Something was telling the ECU to fully open the ISCV valve. Trawled the forums to find this post: http://www.ae86drivingclub.com.au/forums/showthread.php/22227-*SOLVED*-Blacktop-20V-High-Idle

The thread says that certain unused load inputs must be grounded, such as the AC. After grounding the AC1 & ACT pins, the idle has dropped to 1500. Leaving it till warm, the ISCV will pull the idle down to 1100. However, whenever driving, the idle goes back up to 1500.

Besides the AC1 & ACT terminals on a stock blacktop ecu, what other unused pins should be grounded?

[the witzl]

have you wired up the speed signal input (normally SPD or something similar)? Perhaps the ECU is out of whack no knowing if the car is moving or not?

[Matt]

http://www.youtube.com/watch?v=tLcVH8DRuEc

I haven't confirmed the video is correct, but found this on you tube a while back and was planning on verifying it, but never got around to it.....

However it might be useful.

[hayashi]

Nice vid. Used it to double check my plumbing, and it's all the same.

Putting the car into diagnostic mode drops the idle back to baseline, around 900, which means that the iscv control is definitely working. Which leads me to believe something else telling the ecu to idle up.