I must be losing my mind, but I cannot find my prior post regarding a phantom vacuum leak--an intermittent whistle at high vacuum. Regardless, I have now found the culprit: The whistle is coming from the EGR vacuum regulating valve (GM P/N 1997171--discontinued). The challenge I now have is that this part appears to be designed to let air in. In addition to the two ports for the vacuum lines for the EGR circuit there is a third "port" with the remant of a foam air filter on it. The whistle is coming from that third port. Is this how this part is supposed to work? Or is this how this part fails?

I know the P/N and its status because I tried to get a replacement from a local dealership. It looks as though I will have to order it from an aftermarket source. I am trying to figure out if it is worth my time and money to pursue. It appears to be a $60 item.

 

In the de-energized position, the solenoid valve allows atmospheric air to vent to the EGR valve vacuum port. This allows the EGR valve to be fully closed by the spring.

In the energized position, the solenoid valve connects the vacuum supply (from the throttle body fitting) to the EGR valve vacuum port, and seals off the atmospheric vent. This allows the vacuum to open the EGR valve.

If the vacuum ines are incorrectly connected, there can be a vacuum leak. If the solenoid valve itself is damaged, there can be a leak.



The upper port (as viewed) should be routed to the EGR valve pilot, and the lower line should be connected to the timed vacuum port on the underside of the throttle body.



If you have this type connector, the outer (gray) line connects to the TB and the inner (black) line connects to the EGR valve.

If you cannot locate a factory replacement part, and aftermarket part should work just fine in this application, since it doesn't require a highly critical calibration of anything in the assembly.

 

Thank you Vader for the explanation of how this solenoid works--especially the reason for the air inlet on the back side.

Yes, my connections are as in your photograph and everything is routed as it should be. From your explanation of how this valve works it appears that I do have a vacuum leak in the solenoid. I will get to work getting a replacement.

Thank you for your help. As I have been searching through this forum looking for answers I am impressed by how much you do to make this forum an asset for everyone. Your replies are a marked contrast to the many replies I have found in which the inquiring party was belittled by someone just because they asked a question. Thank you again for your help.

 

When E. F. Vader speaks, everyone listens.

 

So that plugs in to the open hole here:

 

no, that I believe goes to the canister purge tank. the EGR vac. fitting is on the underside of the throttlebody.