Hello everyone. 258, Manual, 1988. Last weekend I swapped out my Weber K551 for my newly rebuilt Carter. It starts great and, after it warms up, runs great, but when I start it cold, it runs at fast idle for 2-3 seconds, then drops to about 600, running very, *very* rough for about a minute. Situation stays the same if I rev it higher. Then it goes back to fast idle and runs fine from there. Sounds like detonation, or like it's only firing on two cylinders - a neighbor heard it and thought I was revving a Harley V-twin. Can't figure it out. Almost positive I have all my vacuum hoses connected right, and I replaced my O2 sensor at the same time as the carb. Installed new spark plugs today, (the cap, rotor, and wires only have a few thousand miles on them) new air filter, I can't figure out what the problem is. Any suggestions as to the cause of the trouble? Thanks all.
-Micah