Trying to raise my idle a bit and the screw on top of the intake manifold no longer has any effect? why?

 

thats the air bleed screw, it usually does effect idle speed a little bit but it sounds like you need to adjust the throttle plate screws which control how much the plates are open when the car is idling, try messing with those but be careful it only takes a little bit of adjustment to get them where they need to be and easy to open them too much. you should warm up the car fully and adjust them. my opnion atleast, i had the same problem once as well.

 

DON'T mess with the throttle plate adjustments. Unless someone has changed them in the past, you have no reason to change the factory settings.

If the idle set screw has little effect, it's likely that you have a vacuum leak somewhere else.

 

This is true. I have had this problem for a good year now. My car idles perfectly at 650. I can't make it go lower or higher (Unless the car is cold then it goes through its normal proceedings...) I can hear a vacuum leak, but I can't find it. I have dumped can after can of carb spray/ some sort of fluid to see idle go up or down. I can't find it.. im thinking maybe under the plennum again...

Point being I used to be able to adjust the idle, but now since this leak started I can't, its stuck at 650... So I would definately agree to this statement.

 

The leak may be caused by a hole in one of the vacuum hoses. There was a thread on here a while ago that showed how to make a device that will blow air into the intake (while the engine is off and throttle plates are closed) and you can check to see where it escapes from. I'll post the link, but the thread is old and the pictures aren't there anymore. Maybe you can send a PM to the guy who originally posted the pics and see if he will email some pics to you.

https://www.rx7club.com/showthread.p...ighlight=leaks

 

Driving an RX7.