TVIS not engaging due to ECU?

[phrostbyte]

Hey peeps,
This is actually a problem I had ages ago which was rectified by replacing the ECU. Basically I had an ECU with an orange sticker (I think AE82 Twincam), and when it was plugged in, the TVIS would never get the signal to close on low RPM. When I plugged in my new dark blue sticker ECU, it engaged straight away, no wiring changes no nothing.

I'm wondering whether possibly this could have been a slight wiring difference between ECU models? Anyone encountered this problem before? My cousin is now using the orange sticker ECU in his AE86 and it's driving him mad having sluggish power below 4150RPM....

Cheers,
Kev.

[JustCallMeOrlando]

As far as I know, the solenoid which controls the TVIS is normally open, and gets pulled closed by the ECU. By saying normally open, I mean it holds the butterflies closed using vacuum. Perhaps his solenoid is stuffed. I can't see Toyota switching the way it works like that.

[phrostbyte]

Hmmm.
Yeah it would seem that there is a constant 12V stream through one of the wires to the TVIS VSV, and I think the other wire is grounded by the ECU whenever it's between 0 and 4150RPM. There is a small vacuum storage tank right next to it which enables it to store a certain negative pressure of vacuum, enough to instantly close the TVIS whenever it likes, and stores enough vacuum to even close the TVIS butterflies while the engine isn't running (ie. switch on ignition, detect 0RPM, close butterflies).

*shrugs*

Kev.

[JustCallMeOrlando]

Yep, there is 12V going to one side of the solenoid, and it's grounded by the ECU. The ECU does this *above* 4150rpm though. Below 4150rpm, the solenoid is off, and it's normally open, thus using vacuum to pull the butterflies shut, and when the solenoid is closed, they are spring-loaded open.