CIS help idle won't come down 83 SC with Lambda
 

I just installed a new pop off valve in my airbox and throughly cleaned the airbox. The old valve was loose and would pop out on a slight backfire. Now it starts and idles fine but when I give it gas the idle will not come back down. It will sit at around 1500 rpm. When driving if I push in the clutch the idle will stay high. If I slow the car down with the engine to 1000 it wil stay there untill I give it gas and it is back up! I was sitting at a stop light at about a 1000 rpm idle and it went by itself to over 2000 rpm. Before I replaced the pop off it would start but idle low and die or backfire slightly until warm. The car seems to run well and doesn't smell rich or lean and the tailpipe is a gray color and not black. I know there is probably a post about this but I can't find it so please point me in the right direction or give me some ideas.
Thanks, Jeff

Sounds like your new pop off valve is leaking. My advice would be to test it for leaks at idle with an unlit propane torch or carb cleaner .

I will check it out! Thanks

IF that is the only change.....the leak is at the air box.

Hey Guys, I did the propane test and there were not leaks around the NEW pop off valve. The problem was the old valve had come loose from the epoxy and created a large vacuum leak and PO had screwed with the mixture and idle speed adjustments to make it run. With a little help from a friend we did get the idle and mixture right and all seems well. It starts with no backfires (as it did before) and acelerates better than ever. I also plugged the decel valve and that cured the idle hanging up. Damn it's almost time to put her away and now it is finally running good!

Jeff