Carb issues at low rpm

[egleaves]

Engine sputters and bogs at idle and low RPM.  I can get it to smooth out once I'm moving, but I have to basically pump the accelerator lightly to keep it from dying.  Cruising above 2K RPM feels ok until I reach a hill....

Distributor is new.  Timing is within tolerances.  Power valve has been replaced.  Choke is freshly adjusted.  Accelerator pump is squirting.

It wasn't running well, so I diagnosed and found the choke wasn't opening fully when warm.  While working on the choke I touched the 12V power to the intake manifold and blew a fuse.  Replaced the fuse, adjusted the choke.  All seems well there.

I also installed a new cap & rotor.  In a hurry.  In the dark.  Turns out I dropped the ground strap when transferring the coil to the new cap.  The ungrounded coil made some clicking sounds (like an arc) and then the whole thing shut down.  Local parts store confirmed that I fried the module inside of the distributor.  So I got a new Accel distributor.  All seems well there.

Took it for a quick test drive with the new distributor and it felt great!  Drove to work the next day and it got sluggish.  On the way home I could barely keep it running.  It even died at some very inopportune moments.  I got it home and changed the power valve, checked the timing, and verified that the accelerator pump was working.  All seems well.

Whatever is wrong seems like it got worse as the day went on, and as the engine got warmer.  Number one plug is reading a bit lean....I didn't pull the others.  I've been running this carb for 8 months (with very few problems) and all I've messed with is the choke and the curb idle screw.

I need some help brainstorming what to check next!

[Irish_Alley]

major vacuum leak? have you checked for vacuum leaks yet?

[rdhack]

You didn't by chance get your plug wires crossed??

[egleaves]

Vacuum is my no. 1 suspect right now.

"Cold" started the engine this afternoon and it fired easy enough, but tapered out and quit. I could repeat this over and over. Start. High idle. Slowly die.

I unhooked the dist vac line and put my vac gauge on the carb port.  This made the truck able to idle. Low, but steady. Pulling a little over 5" vac.

I suspect the problem is with the vacuum advance. Could the vac advance diaphragm be bad?  Could this indicate my timing is off by a tooth?

[rich weyand]

FIVE INCHES of vacuum??  Oughta be more like 18!

Let me guess.  You have the vacuum advance connected to ported vacuum.  Change it to manifold vacuum and see what happens.

Oh, and you should know to never, EVER, work on anything electrical without disconnecting the ground from the battery.  Little slips can get very expensive when working on a live electrical system.

[egleaves]

It's pulling 5" at about 400 RPM.  Barely running.

The vacuum advance is connected to the dedicated port on the primary metering block.  It has been connected there for the past 10 months without these symptoms.

Oh, and you should know to never, EVER, work on anything electrical without disconnecting the ground from the battery.  Little slips can get very expensive when working on a live electrical system.

I do know this, but I'm a little hard headed sometimes.

[egleaves]

 With the choke on it idled long enough for me to check the timing. 4-6 degrees btdc.

 Now it's warm and won't idle long enough to read the timing. Unless I disconnect the vacuum advance and plug it at the carb.

 Then it would Idle at super low RPM and the timing read 4-6 degrees AFTER tdc.

Is that normal?

[egleaves]

I guess I fixed it. With the vac advance disconnected I got the base timing to 10-12. Hooked up the advance and fiddled with the idle,  now it runs great again.

[rich weyand]

Probably what happened is that the distributor wasn't clamped securely enough, and when the weather changed, the disti loosened up enough to drift retarded.  The disti housing always drifts retarded when loose, because that is the direction the shaft rotates in.  BTDT.