Smoke test and EGR modulator

Good afternoon.

Is this what you are talking about?

This is called a VSV valve.

Roy

Thank you! No, it is the EGR vacuum modulator with diaphragm in it. Might be specific to Toyota?

Okay, got it. Yes these do have an relief in them so you might see a little smoke. These have a high failure rate so if the smoke is excessive I would replace it.

Thanks a lot Roy! Yes it is the part. must be the diaphragm broken. I have been chasing for a reason why rpm behaves erratic after cold start, this should be it.

You are welcome.

Roy

Hi Roy or any other pros,
Please excuse me for bringing this topic back. With manuals etc, I did thorough tests on my EGR modulator both on-vehicle and off (with vacuum gauge). All indicate this part is still good.

And per some readings, the EGR modulator (at least for Toyota) is designed to be open to air at engine off. So I am very confused, as leaking smoke appears to be normal during a smoke test for vacuum leak. Any advice appreciated.
-Simon

It could be vented to the atmosphere when the engine is off. Does the new part do the same thing?

Thanks Ken. I did not replace it. I did a couple of tests particular on the modulator: (1) Sealed the vent hole with a piece of tap and (cold) start the car, idle still behaved the same. (2) Spray carburetor cleaner to the modulator after cold start, no change to idle. So this part must be good.

You are right that the modulator is open to air when engine off. Just so surprised that this was never noted anywhere as to vacuum leak test.

Yep, this is not typical so most miss it. Use 2CarPros anytime, we are here to help. Please tell a friend.

Cheers, Ken

Sure will do. This is a great site for DIYers with nice pros help. Thanks Ken.
-Simon