20V inconsistent VVT

Army Fork
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20V inconsistent VVT

Postby Army Fork » Sun Nov 30, 2014 11:46 pm

Anyone ever experience a breakdown of their 20V's VVT? I'm uncertain but I believe my pulley may be failing. Power is inconsistent, sometimes under heavy throttle I get a nice pull and other times the engine seems like it's choking off, there doesn't seem to be rhyme or reason to when it happens either. I plan on wiring in an LED to make certain that the VVT is actually getting the signal, but for now I could use some feedback on your guy's experiences
1984 SR5-GTS 20V ST/BT coupe.
- Stance GR+ Coilovers
- Mishimoto Cooling
- T3 adjustable 4-bar, Panhard, traction brackets, tension rods
- T3 Short shift
- Manual rack conversion
- Blacktop electronics

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onnaj
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Re: 20V inconsistent VVT

Postby onnaj » Mon Dec 01, 2014 12:29 am

I had the same with my Celica AT200 with blacktop swap. Sometimes it pulled straight away but sometimes it hesitated a bit, a feeling as if the vvt is kicking, then vvt off, then on again, etc.

I couldn't find a solution for it. I had all ignition parts brand new and the engine was stock.
Check my 4AGE 20V BT teardown, rebuild and transplantation over here --> http://club4ag.com/forums/viewtopic.php?f=7&t=3382

Army Fork
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Re: 20V inconsistent VVT

Postby Army Fork » Mon Dec 01, 2014 2:32 pm

I believe my VVT signal is good so I'm thinking mechanical. Sounds like you had the same issue
1984 SR5-GTS 20V ST/BT coupe.
- Stance GR+ Coilovers
- Mishimoto Cooling
- T3 adjustable 4-bar, Panhard, traction brackets, tension rods
- T3 Short shift
- Manual rack conversion
- Blacktop electronics

yoshimitsuspeed
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Re: 20V inconsistent VVT

Postby yoshimitsuspeed » Tue Dec 02, 2014 8:45 pm

Very unlikely it's the VVT. It can't really be felt by the seat of the pants. I suspect you have another issue.

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Resurrected
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Re: 20V inconsistent VVT

Postby Resurrected » Tue Dec 02, 2014 10:37 pm

May be worth looking into...... http://forums.club4ag.com/zerothread?id=85825

Make the necessary checks to TPS for proper function and adjustment. Check the o2 sensor as we'll for proper function (you can use a DMM for this although a lab scope would be preferred). Apparently 20v's are picky in regards to the quality of the sensor. It may be worth the investment to buy a denso unit if you havn't already. Also are you using an afm?
Last edited by Resurrected on Tue Dec 02, 2014 10:52 pm, edited 1 time in total.
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Army Fork
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Re: 20V inconsistent VVT

Postby Army Fork » Tue Dec 02, 2014 10:50 pm

Running a Denso or a Bosch, can't remember. The power output is really inconsistent, sometimes it gives me everything and other times it really feels lacking, kinda curious as to whether or not it might be the TPS.
1984 SR5-GTS 20V ST/BT coupe.
- Stance GR+ Coilovers
- Mishimoto Cooling
- T3 adjustable 4-bar, Panhard, traction brackets, tension rods
- T3 Short shift
- Manual rack conversion
- Blacktop electronics

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Re: 20V inconsistent VVT

Postby Resurrected » Tue Dec 02, 2014 10:58 pm

Check for any glitches in the TPS with a DMM. Make sure that it is adjusted properly as well. Check the FSM for the specs on that but most cars will be less than 1v with the throttle closed, and will increase to about 5v at WOT. Test with the key ON and the engine OFF just so you're not revving the nuts off the engine while testing.
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Army Fork
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Re: 20V inconsistent VVT

Postby Army Fork » Tue Dec 02, 2014 11:06 pm

When I was working on it I remember the TPS showing a good signal but I'll have another go at it after finals
1984 SR5-GTS 20V ST/BT coupe.
- Stance GR+ Coilovers
- Mishimoto Cooling
- T3 adjustable 4-bar, Panhard, traction brackets, tension rods
- T3 Short shift
- Manual rack conversion
- Blacktop electronics

onnaj
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Posts: 524
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Location: Netherlands

Re: 20V inconsistent VVT

Postby onnaj » Wed Dec 03, 2014 4:14 am

I've also bought a new tps (and set it up by the manual) and oem o2 sensor and the problem didn't solve. At WOT your o2 sensor can't be the problem, cause it running in open loop then i think.
Check my 4AGE 20V BT teardown, rebuild and transplantation over here --> http://club4ag.com/forums/viewtopic.php?f=7&t=3382

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Re: 20V inconsistent VVT

Postby Resurrected » Wed Dec 03, 2014 7:42 am

onnaj wrote:I've also bought a new tps (and set it up by the manual) and oem o2 sensor and the problem didn't solve. At WOT your o2 sensor can't be the problem, cause it running in open loop then i think.


Correct. The ECM operates in open loop during WOT. If either of you guys are running AFM's I would suggest testing them for proper operation. The MAP sensor as well can cause bogging issues in my experience if it is the wrong one or not working correctly.
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Army Fork
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Re: 20V inconsistent VVT

Postby Army Fork » Wed Dec 03, 2014 8:41 am

I moved to a blacktop electronics setup because I had issues with the AFM. I'll swap in a different MAP and give it a go, see if the problem resolves itself. I'm also going to disconnect the VVT and see if the effect is related, although this may throw a code
1984 SR5-GTS 20V ST/BT coupe.
- Stance GR+ Coilovers
- Mishimoto Cooling
- T3 adjustable 4-bar, Panhard, traction brackets, tension rods
- T3 Short shift
- Manual rack conversion
- Blacktop electronics

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Re: 20V inconsistent VVT

Postby Resurrected » Wed Dec 03, 2014 9:07 am

Don't worry about it throwing a code. If it does throw a code it should clear itself after it's reconnected and the ignition is cycled off and then on again.
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Army Fork
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Re: 20V inconsistent VVT

Postby Army Fork » Wed Dec 03, 2014 9:12 am

The reason why I'm concerned about the code is that it may put the car into limp or at least a reduced map. Not worried about hurting the engine or anything, that's why the diagnostics exist. I'll try to give it a go in a bit, in finals right now
1984 SR5-GTS 20V ST/BT coupe.
- Stance GR+ Coilovers
- Mishimoto Cooling
- T3 adjustable 4-bar, Panhard, traction brackets, tension rods
- T3 Short shift
- Manual rack conversion
- Blacktop electronics

muythaibxr
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Joined: Sun Jan 13, 2013 8:51 pm

Re: 20V inconsistent VVT

Postby muythaibxr » Tue Dec 09, 2014 5:33 pm

yoshimitsuspeed wrote:Very unlikely it's the VVT. It can't really be felt by the seat of the pants. I suspect you have another issue.


VVT can be felt, especially in mid-range RPM... It can also be heard, especially with open throttles.

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