There was an annoying rattling sound coming from the area around my intake manifold. I finally found it. The aux. port valve actuator has a plate that limits the travel in both directions. The screws that hold down the plate were missing from one of the actuators and the plate was rattling around. I am wondering two things:

1) How could the screws have come loose?
2) How could this effect performance?

Any ideas?

 

Sometimes things just loosen up after 20+ years. It's probably an M4 screw. Just replace it. The biggest problem is that it might be jamming up the actuator and/or creating a vacuum leak.

 

Actually two screws (an M4 and an M3). My first thought was that the screws vibrated loose over time and maybe they did. But, I think someone performed a repair at some point and failed to put them back.

I am most curious about how it could impact performance. I speculate that it might cause sluggish performance since the port valve wouldn't be functioning correctly (i.e. a vacuum leak). I will find out today as I am putting things back together and firing it up.