By
gschwell, January 6, 2011
Hi All,
Concerning my 2003 with auto transmission:
What I think is my EVAP vacuum switching valve is clicking like crazy. Just to make sure I'm talking about the correct part, its attached to the air intake, near the MAF. After the car is warmed up the valve constantly clicks, not necessarily in even intervals.
When I unplugged the blue wiring harness the clicking stopped.
No CEL.
Any ideas on where to start with this?
I'm wondering if its one of the sensors?
Yes, those are EVAP VSV valves and they can be quite noisy. Most owners won't even notice it, unless they've modified the intake/airbox or switched to an aftermarket intake. As they make use of a solenoid inside to act as the switching valve, over time it can get excessively worn and make noise. Varies from car to car - some seem make little to no noise with over 100K miles, and others could be under 30K miles and click loudly enough to be heard by people outside the car.
Replacing the VSV will likely eliminate the noise, but a noisy valve is still operational. Personally, I'd wait until it completely fails before I'd replace it - just crank up the radio a bit more to drown out the noise.
I only hear if when I open the hood. I just figured it wasn't supposed to open and close with such frequency, but if its normal than it doesn't bother me.
Thanks again for the great info.
Garth
In the last two months, I have also noticed the my EVAP VSV is also clicking like crazy. Mine clicks so fast that I thought it might be valve tapping at first (about 2-3 Hz) until I tracked it down. I know the VSV is being commanded directly from the computer, and I am not getting any check engine light either. If it is normal, I could use an education, I can't imagine why any valve would need to be opened and closed so quickly during idle. Would vacuum line leaks cause different behavior? But I would think that leaks would throw a code. I also have a 2003, by the way.
That particular VSV is better known as the PWM vacuuming-switching valve. Commanded by the ECM to "bleed" vacuum a little at a time. The rapid cycling time is required to precisely control how much vacuum is passed through the valve. Usually most noticeable at idle, as the vacuum is highest at that point. They could have made it cycle less, but the valve can handle it and it fits the EVAP strategy they have implemented on the car.
Great info, fish! It's a good thing that the valve is working properly (even if it is getting louder), because I notice that neither Advance, Autozone, or Rockauto has a replacement in their catalog. So if it did go bad, it would be a dealer item... $$$
One more thing just to drive this thread into the ground. I have some troubleshooting info on this particular V3 VSV EVAP valve from the Toyota service manual. (Which doesn't say how fast the thing switches in operation, or how loud it should be.) I figured I would write it down for the next guy who finds this thread. These are the four steps to check if the VSV is working or not.
1. Use ohmmeter to check resistance of the solenoid coil. (The resistance between the two pins on the VSV connector). Should be 27-33 Ohms at room temp.
2. Check that neither of the two pins is short circuited to the body of the VSV itself.
3. With the VSV disconnected (and the hoses pulled off), air should flow from the input to the output. The input is the hose pointing in the same direction as the electrical connector.
4. With battery voltage applied to the VSV pins, no air should flow.
