Ran rough when cold

[Paul]

My 3AC ran really bad when it was cold. When it sounded like it was misfiring, I pulled plug wires one at a time and found the front cylinder was totally dead when cold. Once it warmed up, it ran great. I made the incorrect assumption that the rings were stuck on the #1 piston, and it sealed somewhat when it warmed up (I need a compression gauge).

It seemed to be getting worse, so yesterday I was poking around and noticed raw fuel leaking around the exhaust manifold flange. I checked the carb while it was running, and it looked like fuel was dribbling in from the accelerator pump nozzle. I disconnected the vacuum line from the auxiliary accelerator pump (AAP-round thing on front passenger side of carb) and the idle instantly cleared up, while I noticed fuel in the vacuum line.

The pump diaphragm must be shot, and for now it runs great disconnected. The purpose of the AAP is to improve cold engine acceleration. I'd rather take it easy when the engine is warming up, so I'm not missing it at all.

So, if your having trouble with rough cold idle, try disconnecting and plugging the vacuum line to the AAP (this is the line from the bottom of the TVSV). This step should be part of the troubleshooting process.

Edit - Just found Sherlock posted this fix earlier. He had the same symptoms... #1 cylinder dead when cold.

[GTSSportCoupe]

Thats very interesting, thanks for sharing! My last carb had issues with fuel dribbling down as you described. It didn't cause any misfiring, but the car consumed lots of fuel and idled crappy.