This morning I started my car. It died the first time (usual occurrance for cold weather) but I got it started. It would not do a fast idle, which is unusual since I replaced the carb with an Edelbrock only about 8 months ago, and it never had problems fast idling before. After warming up the car I drove to work (only about 5 minutes away) and when I was turning in, the engine idle suddenly dropped to about 400 RPM (I have it set for 700) and began to run very rough. It reminded me of driving a vehicle on a couple less cylinders. Anyway, I couldn't do anything because I had to start work, but went out to try and figure it out on my break. It started fine and seemed to be running a bit better, but the idle was still low so I increased it to about 800. After work I went out to start it, the idle sat at about 1000 when I first started it (wasn't standard fast idle, couldn't get it to kick down) but after I started driving it dropped to about 500. I noticed a severe loss of power and the engine running rough whenever I applied throttle. It isn't making any different noises, but you can feel the engine vibrating more.
My car:
'85 Z-28
305, 4bbl Edelbrock 600 CFM carb
5 speed manual
Pretty much everything is stock besides no EGR, no cat. conv., and new carb.
Anyone have any ideas what the problem might be?

 

Take off the air cleaner and see if your choke is working right. Might just need some carb cleaner on the linkage.

 

The choke works fine, free movement and comes on during start... I talked to one of the mechanics where I work and he said it sounded like water/ice in the fuel, so I put in some de-icer and water remover and let it run for an hour this morning before driving it... the car idled and ran after that, and was driveable, but there is still a noticeable loss of power, and it vibrates pretty badly at idle (set it back to 650). Also, there is now some serious black soot all over my bumper around the exhaust, could this have been caused by the de-icer? And no, it's not my mixture, before anyone mentions that.

 

Try richening up the choke a little bit. It may be set too lean for colder weather. My Holley is like that once it starts to get really cold out, I just richen the choke a little bit - problem solved.

I usually set the choke about as lean as I can though, while still rich enough for the engine to start and run properly while its cold... come spring, I'll lean it out again. Has yet to cause any problems for me, doing it this way.

 

Already did. Also readjusted the idle mixture.