Air Intake Control Valve(ACIS)

[Rob_0126]

I believe I found out why my fuel mileage has suffered. My 92 Camry V6 is a rebuilt (900 miles) and Ive been getting 19 mpg highway.

I noticed the ACIS was not closed at idle or at any engine speed for that matter. So in other words, it was set to wide open (only should be round 3500 rpms), so more air ='s more fuel.

And my low end was suffering big time.

Thought that was odd, so I bypassed the VSV, put straight vacuum on it, and now low end is back, runs good on wide open, but of course not super because it's still getting full vacuum, and not controlled by the VSV.

So, not sure if the VSV is stuck open or closed. My guess is closed.

Any of you pros got an idea which it is?

[Kep]

Non Californian VSVs: Below 140 F (auto trans) there should be no vacuum at 2500 RPM. Over 140 F there should be low vacuum at 2500 RPM.

To inspect the VSV disconnect the hoses. Resistance between the contacts should be between 33 & 39 ohms when cold. If no continuity--replace the VSV. Next check each contact for continuity with the body of the VSV. If either shows continuity to ground replace the VSV. Next, apply 12 volts across the contacts and blow through port E (the one nearest the filter). Air should flow out the bottom, port G. If it doesn't replace the VSV.

Luck,
Kep

[Rob_0126]

Originally Posted by Kep

Non Californian VSVs: Below 140 F (auto trans) there should be no vacuum at 2500 RPM. Over 140 F there should be low vacuum at 2500 RPM.

To inspect the VSV disconnect the hoses. Resistance between the contacts should be between 33 & 39 ohms when cold. If no continuity--replace the VSV. Next check each contact for continuity with the body of the VSV. If either shows continuity to ground replace the VSV. Next, apply 12 volts across the contacts and blow through port E (the one nearest the filter). Air should flow out the bottom, port G. If it doesn't replace the VSV.

Luck,
Kep

Shouldnt the ACIS be closed at idle? Doesnt make sense to me for the VSV to not allow vacuum to it. Sticking straight vacuum to the ACIS, I get a lot better response on the bottom end because it is closed then. Am I missing something on how this system is suppose to work?

thanks for the heads up on testing the vsv.

[Kep]

My I4 doesn't have an ACIS so here is what I have read:

* ACIS (Acoustic Control Induction System)
ACIS includes a valve in the bulkhead separating the surge tank into two parts. This valve is opened and closed in accordance with the driving conditions to control the intake manifold length in two stages for increased engine output in all ranges from low to high speeds.

The engine control module judges the engine speed by the signals ( (4), (5) ) from each sensor and outputs signals to the TERMINAL ACIS to control the VSV (Intake air control).

There is also the intake air control valve attached to the air intake chamber. Part of the ACIS, the ECM provides signals to the VSV to open or close. This valve opens or closes the vacuum source to the actuator, which in turn opens or closes the intake air control valve. The intake air control valve is designed to modify the effective manifold length in 2 stages for increased power in all driving ranges.


From what I am reading, the ACIS should not have a vacuum at idle (at least when cold). I don’t know if the vacuum actuates the ACIS or shuts it off. Once you establish that there is no vacuum at idle, then quickly goose the gas pedal to full open and there should be a momentary spike in the vacuum (when the actuator rod is pulled out.)

You should be able to put a 26.7 kPa vacuum on the IAC valve and the rod will move. Leave the vacuum on for a minute, the rod should not move again (otherwise a leak is indicated)

I don't know if that is helpful or not. There is quite a bit about it in the manuals.

Kep

[Rob_0126]

Originally Posted by Kep

My I4 doesn't have an ACIS so here is what I have read:

* ACIS (Acoustic Control Induction System)
ACIS includes a valve in the bulkhead separating the surge tank into two parts. This valve is opened and closed in accordance with the driving conditions to control the intake manifold length in two stages for increased engine output in all ranges from low to high speeds.

The engine control module judges the engine speed by the signals ( (4), (5) ) from each sensor and outputs signals to the TERMINAL ACIS to control the VSV (Intake air control).

There is also the intake air control valve attached to the air intake chamber. Part of the ACIS, the ECM provides signals to the VSV to open or close. This valve opens or closes the vacuum source to the actuator, which in turn opens or closes the intake air control valve. The intake air control valve is designed to modify the effective manifold length in 2 stages for increased power in all driving ranges.


From what I am reading, the ACIS should not have a vacuum at idle (at least when cold). I don’t know if the vacuum actuates the ACIS or shuts it off. Once you establish that there is no vacuum at idle, then quickly goose the gas pedal to full open and there should be a momentary spike in the vacuum (when the actuator rod is pulled out.)

You should be able to put a 26.7 kPa vacuum on the IAC valve and the rod will move. Leave the vacuum on for a minute, the rod should not move again (otherwise a leak is indicated)

I don't know if that is helpful or not. There is quite a bit about it in the manuals.

Kep

I dont know myself. Doesnt make sense to me that the VSV doesnt close it at idle since you dont need the extra air/fuel ratio. My cars VSV doesnt allow vaccum to the ACIS at all. I can only guess this is why Im getting 19 mpg avg.


By passing the VSV, running the straight vacuum, I see more power on the low end, and the high end (above 3000 rpms) doesn't suffer hardly at all.

Should I replace the VSV and how much does that piece of plastic go for these days :/

thanks

Robert

[Kep]

Originally Posted by Kep

To inspect the VSV disconnect the hoses. Resistance between the contacts should be between 33 & 39 ohms when cold. If no continuity--replace the VSV. Next check each contact for continuity with the body of the VSV. If either shows continuity to ground replace the VSV. Next, apply 12 volts across the contacts and blow through port E (the one nearest the filter). Air should flow out the bottom, port G. If it doesn't replace the VSV.

Before you replace the VSV check it for proper function. It may be fine and something else is causing the incorrect operation.

Kep

[Rob_0126]

thanks, ill check it out and get back some time.

[Luckynumber5]

19 mpg average sounds about right. The 3vz-fe runs rich from the factory to keep emissions and horsepower down. The 3vz is one of the few freak engines Toyota engineered and decided to tone down for use in the Camry believe it or not

[Lumberg]

The ACIS is designed to open at higher RPMs to give better high end performance.

You want it closed up to at least 2-3000 RPM.