For some reason or another my car started running too rich. I'm not sure when it started, but I know it was fine right after I rebuilt it. It may have been when I took the air horn off to re-adjust the lean stop screw a few weeks after the rebuild, or it might have been recently when it started shaking more when I drive. Check sig for setup, it's a CCC q-jet.

In closed loop at idle, the dwell is fixed at right about 45 or 50. When cruising or on deceleration it also goes to this value. Adjusting the lean stop screw and rich stop screw has no effect except at one point where the dwell goes to a fixed 30 and the engine sounds like it's about to die. The original place setting was with the rich stop screw all the way into the air horn and the lean stop screw 4/32 down from that. That's the setting I put it back on every time I mess with it. As far as I can tell the MCS is functioning the same as it always has.

The idle mixture screws are 7 turns out. The idle air bleed valve doesn't seem to affect the dwell. The oxygen sensor is a brand new AC Delco unit, and it reads about 0.7 while the dwell is at 45. The CTS and the TPS are working correctly. I unplugged the manifold vacuum line and the PCV vacuum line to try and lean it out and the oxygen sensor voltage dropped to about 0.45 and the dwell dropped to 30. I also unplugged the charcoal lines and put them back to see if that made any difference, which it didn't. This all leads me to believe that the ECM is working just fine.

Also, when I rebuilt the carb I epoxied about 6 places on the bottom of the fuel bowl and I'd like to think I did a pretty good job.

As for the ignition, the cap and rotor are brand new. The brush is a low-resistance piece, and it looked fine so I re-used it. The plug wires are about a year and a half old. The spark plugs are only a few weeks old, I replaced them at the same time as I rebuilt the carb. I'm currently running my original EGR valve that seems to be working just fine, and it is hooked up straight to the ported vacuum port on the carb.

Any ideas or suggestions?

 

not sure if this will help or not but.(not an expert)
when I turned my mixture screw out 7 turns a while back after reading a post on the board , my dwell read 45*. Could not adjust it at all with the idle air bleed screw.
I started to turn the mixture screws 1/2 turn in at a time until I could adjust the dwell to 30* with the IAB. not sure if that will help your runnng rich but maybe help you adjest your dwell

 

Now that I think about it, I did mess with those screws about the same time i was setting my timing a week ago. BTW I found out my spark plug wires are bad, and I ordered some new ones.

 

That might be it actually, and I think I know what happened. A few weeks ago I was adjusting those screws and the IAB to smooth out my idle. I got it smoothed out, but the dwell must've been fixed but I was so happy that my idle was smooth that I didn't notice whether the dwell was varying or not.

New question, I can adjust those screws and the IAB to a point where the dwell varies from 25-35, but the idle sounds like crap. If I turn the IAB in, the idle will smooth out but the dwell will stay fixed. Is it possible to set the IAB to a certain setting and then turn the idle mixture screws to a point where the dwell varies between 25 and 35? There isn't a letter on the valve that I can see BTW.

 

They say that you adjust the dwell with the IAB .
So i guess if you have it at the proper dwell you could turn the screws out a little at a time to see if it helps the idle.
Also you could turn the idle screw in a little to step up the RPMs
Hope this helps