I recently obtained an 87 Subaru GL that has a hard time warming up and idling when warm. I have noticed, that the anti after-burner valve seems to be stuck in one position. When the car is sitting, trying to hold an idle, the valve is constantly trying to suck in air. If I cover the bottom of the valve, the idle come up significantly.

 

I'm going to be working on the car later today and I'm going to attempt to cover most, if not all, of the bottom of the valve, to stop the constant air sucking. I know that this valve is supposed to prevent backfires at high speed, like over 3000rpm. If it is covered and can't due that properly, what might happen, besides backfires which I dont really want either. Would it be ok to cover most of the valve? Any idea how much a new one would cost?

tape a quarter over the hole.

I taped the bottom of the valve over and now the car idles great. A bit high but I'm going to be adjusting that soon. I took it on the highway afterwards and it ran fine, no backfires or popping like I read about. I'll be getting a new valve to replace the one I disabled, but I'm glad to have fixed this issue.