HELP: Slight A/F adjust, now won't start

[SoCal911SC]

So the idle on my '82 SC has been hunting more lately and has been erratic since the cold weather has set in. And I've noticed more soot on the garage floor when starting up and idling, so I thought i'd give it a very slight adjustment to the lean side with the 3mm hex tool.

I made the adjustment and kept the tool in-place and the car started up beautifully. It was still slightly hunting, so I started to give it another slight adjustment counter-clockwise and whenever I'd touch the tool, the idle seemed to react.

When I pushed down slightly on the tool the idle became steady and when i'd let go it would go back to surging, and when I tried to pull the tool out, the car almost died.

I shut the car off and went back and removed the tool from the mixture screw. I then went back to try and start the car and nothing, doesn't start up. I even repositioned the A/F back to its original setting and still nothing.

How are these CIS systems THAT sensitive?? Now I'm not sure what to do because its back in its original position and still not starting. Any thoughts?

Should I have someone push down on the tool while I try to start and then make the adjustment from there?

Thanks.

[gazzerr]

If you leave the tool in, the sensor plate won't be able to move properly. When you pushed down on the tool you were leaning it out because you were pushing down on the sensor plate. If it was surging and then smoothed out that's a good sign you are running too rich. This is common as previous owners tend to mess with the mixture as the system ages and develops vacuum leaks. It gets richer and richer. It's just hiding other issues.

If you take the snorkel off the airbox can you reach in and move the sensor plate up freely? Perhaps it's stuck. When you said a "slight adjustment" how far did you turn the mixture screw? 1/8 of a turn is considered a significant adjustment.

You can't really just play with the mixture. You need to make sure that all your fuel pressures and all the CIS components are in spec and that you have no vacuum leaks in the system. Once the system is up to spec then you can adjust the mixture.

When I first got my car it was running super rich, lots of soot and the O2 exhaust sensor was not functioning. I had numerous air leaks and a bad WUR and leaking deceleration valve on my '82 SC.

Check out this go to thread:

CIS Troubleshooting for Dummies

You can go through that and find out why it won't start.

G.