Help: Rough cold idle

[visionguru]

My car recently developed a problem: when first start up a cold engine, the idle is very rough, and the whole car shakes. If I hold the gas paddle for 1min, then the car kicks into fast idle, after that, everything is fine for whole day, until the next morning.

Anyone experienced this? This happened since several really humid days, and I happen to put some 87 gas in it (it's been using 92 all the time.).

Any hint will be greatly appreciated.

[racerx]

well if you got a normal compression stock engine, 87 octane should be workin just fine. i doubt that caused the problems, unless it has a ton of water in it...

have you touched anything under the hood? modified anything lately?

i would check vacuum lines first, then gaskets and stuff around the carb and intake manifold. maybe spark, cap, rotor, wires, coil...

when was the last time you did a tune up?