I have an 84 Z28 with the L69. I start the engine when its cold, it wont idle alone. I have to give it gas until it warms up when it then idles normal. While its cold, the engine revs like i have a full race cam in it, like one of the cylinders is dead. Why would it do this only when its cold, also It recently started doing this right around the start of winter. I can go out a few hours later when the engine has cooled and it will start right up and idle normal.

 

84,

Welcome Aboard!

Your symptoms could indicate a lean condition on startup. The next time the engine is completely cold (as if it sat overnight) remove the air cleaner before starting. Floor the accelerator or operate the throttle to the full open postion then allow it to return. The choke plate on the carb should have closed fully (or nearly so). If not, the thermostatic element in the choke assembly may be damaged, or the choke linkage may dirty, sticking, binding, or may have fallen apart. If the choke is fully closed, the engine should start after normal cranking. As soon as the engine starts, the choke plate should pull open slightly, then gradually open as the engine warms up. If this doesn't occur, start digging into the choke.

This may help some:

 

another thought... check the vacuum pull off... it is the little gold vacuum canister on the pass side front of the carb... it pulls the choke butterfly back imedeately after the engine starts... pull the vacuum line off the nipple and apply vacuum to it if it does not hold vacuum that may be your problem... usually this problem is accompanied w/ black smoke out the tail pipe...

zroc

ps. don't forget to hail to the overlord...