TVIS Stuck Shut - MR2 Owners Club Message Board
 
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post #1 of 11 (permalink) Old March 27th, 2017, 20:30 Thread Starter
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TVIS Stuck Shut

I have a 91 turbo that I have brought back to life. My issue is that while driving the car kicks on the tvis and shuts the runners and doesn't let them off until the engine is shut off. I cant find the theory on what all activates the system. There are no Codes in the ECM. Car has a boost controller, egr delete. all emissions removed. tvsv removed. I just want to know why. I don't hear knock, timing is spot on, and wide band says it is super rich.
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post #2 of 11 (permalink) Old March 27th, 2017, 21:36
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The TVIS actuator has a spring inside that always keeps the butterflys open, vacuum pressure from the engine closes the butterflys. Everything is contained under the intake manifold, if you want to delete the system quickly you can either remove and cap the vacuum line from the intake manifold or disconnect the connector to the TVIS VSV.

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post #3 of 11 (permalink) Old March 28th, 2017, 06:24
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I would guess that you pulled out the controller for the TVIS along with the EGR system. If it is like the MK1 system, then there is a vacuum valve that opens the TVIS and also disables the EGR through a check valve.
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post #4 of 11 (permalink) Old March 28th, 2017, 17:35 Thread Starter
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Nope. Neither of you are following. The TVIS system is still intact and functional. The ecm is activating the tvis and shutting it down as if it has overboosted or detected knock. To circumvent the systems activation, I disconnected the vacuum supply. This allowed them to open and remain regardless of ecu signal.
The question is/was. What all causes this outcome. What triggers hard tvis shutting.
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post #5 of 11 (permalink) Old April 10th, 2017, 15:33 Thread Starter
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Someone? Anyone?
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post #6 of 11 (permalink) Old April 10th, 2017, 17:06
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I am only familiar with the MK1, but on that car the TVIS is controlled by RPM only. I would expect the MK2 to work the same. I don't think that shutting the TVIS would have a significant role in engine protection. If I was looking at the car for the first time, I would guess that the TVIS VSV was defective or connected wrong.

Did this system ever work correctly after you got the car?
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post #7 of 11 (permalink) Old April 18th, 2017, 19:12
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You sure TVIS is closing? What makes you think it is?

Its default behavior is to "fail open" not closed.
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post #8 of 11 (permalink) Old April 18th, 2017, 19:16
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Chris,

TVIS doesnt SHUT on fail. Its open on fail. In order for the ECU to use TVIS certain criteria need to be met. You need to not be knocking. Theres several others.

You can install a light or just wire a temp one to the TVIS circuit to see what its doing. Its open, it doesnt close until you give it throttle.

So generally lets assume your car is working properly heres like a flowchart of TVIS operation

Steady state cruising - open - throttle/load increase - system check - system OK? - close TVIS if under 4200 RPM - System ok? - keep TVIS closed until 4200 RPM - System OK? Open tvis after 4200 RPM.

if at any time you get a "system ok? NO" TVIS would snap open.

So, again, it fails open. Its open by default, it fails open, the only time it should be closed is if you are in TVIS criteria. Look at the BGB. it has a section for it.
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post #9 of 11 (permalink) Old April 18th, 2017, 22:12 Thread Starter
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Luni, the system opens and closes. it hasn't failed. When the car is first started the TVIS functions as designed it appears untill the first pull with boost. turbo has spun up its first time the ecu shuts the TVIS and keeps it closed. the car then becomes hesitant to boost, and runs super rich. It has currently been bypassed by unplugging the vacuum hose going to the reservoir until I have time to sort this in a few weeks.
Things I will be looking at are
Is my engine warming up to proper temperature. my temp gauge rises quickly but never to the half way tick I have read about. so need to observe thermostat regulation temperature.
Does the ECM require input from the tvsv? mine has been removed and boost is controlled with an apexi unit. i will try plugging it back in and reattaching it to see if it is of any concern. I have not found a definitive answer through search. All I have read is that it stays intact and gets blocked or bypassed.
Also need to observe if the engine bay temp sensor also doubles as an ambient air temp sensor that I have read about. If so that could be an issue as well. With mine plugged in or removed the IC fan runs non stop with key on.
I have confirmed timing to be set as per bgb. I do plan on pulling the valve cover and manually checking cam timing one last time just to be absolutely certain.
Ironicly after this is resolved I plan on installing an rpm switch anyways. I just need this corrected first.
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post #10 of 11 (permalink) Old April 19th, 2017, 00:22
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Quote:
Originally Posted by Chris Murray View Post
Luni, the system opens and closes. it hasn't failed. When the car is first started the TVIS functions as designed it appears untill the first pull with boost. turbo has spun up its first time the ecu shuts the TVIS and keeps it closed. the car then becomes hesitant to boost, and runs super rich. It has currently been bypassed by unplugging the vacuum hose going to the reservoir until I have time to sort this in a few weeks.
Things I will be looking at are
Is my engine warming up to proper temperature. my temp gauge rises quickly but never to the half way tick I have read about. so need to observe thermostat regulation temperature.
Does the ECM require input from the tvsv? mine has been removed and boost is controlled with an apexi unit. i will try plugging it back in and reattaching it to see if it is of any concern. I have not found a definitive answer through search. All I have read is that it stays intact and gets blocked or bypassed.
Also need to observe if the engine bay temp sensor also doubles as an ambient air temp sensor that I have read about. If so that could be an issue as well. With mine plugged in or removed the IC fan runs non stop with key on.
I have confirmed timing to be set as per bgb. I do plan on pulling the valve cover and manually checking cam timing one last time just to be absolutely certain.
Ironicly after this is resolved I plan on installing an rpm switch anyways. I just need this corrected first.
Engine temperature can be a factor in this. Change your thermostat with a Toyota one and see what happens.

TVIS is dependent on throttle position and RPM plus probably engine temperature. The engine temp also dictates boost so that might be a problem too.

Engine bay temp sensor is to control the IC fan. If it is unplugged it defaults to running full speed. This is normal. It doesn't have anything to do with the engine temp or engine ECU as it is a completely separate circuit.
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post #11 of 11 (permalink) Old April 19th, 2017, 13:30
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Chris, I think youre missing what Im saying.

Again, the systems default behvior is to "Fail open"

Meaning, you have something in there that is keeping it closed. THAT is not normal. Its OPEN unless you give it throttle and then it closes. Again, this is why people install TVIS lights.

Its the opposite of TVSV. You sure you dont have your TVSV plug attached to your TVIS actuator? Is that even possible?

Maybe thats it.

TVSV default state is closed. UNLESS certain engine parameters are met. Then it opens.

TVIS default state is OPEN, UNLESS certain parameters are met, then it closes. Both of those actuators are in the same place relative on the back of the intake manifold, and the connectors are the same/if not similiar. So, maybe you need to check that.
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