problem with 88 z24 2.4......please help!

1988 2.4 z24 2wd

i rebuilt the motor in april of 2007 and have sence put over 35k miles on it with no problems. truck has always ran like a dream.

the truck started idling rough and wanting to die all of a sudden one day.
the truck runs like a dream on the highway.

when the truck is cold and you start it, it used to idle up high and stay high, and slowly drop as it warmed up.....now it idles up and then go to slightly higher than normal rough idle when its cold.....and sometimes dies. when you drive it when its cold, it sometimes fall on its face a few times taking off.

the other thing is when the truck is warm and you cut it off for a short amount of time(say your filling it up) when you get back into it and crank it up it idles up high and then idles down spits and shakes and just runs rough as hell for 10 sec and then dies. if you crank it again it just does it again but doesnt run as long. to get it running again you have to "clean" it out. as you are giving it gas and "cleaning" it out if poors black smoke from the tailpipe. and as it come back down(let your foot off the gas) it poors out whitish/ bluish smoke. and once its back to a normal idle it stops smoking and runs fine beside a slightly rough idle.

i drive this truck around 1k miles a week

i have put new wires, plugs, new cat. cleaned the throttle body, changed the timing, and put really good oil and filter on it.......with no change.:banghead:

any help would be awesome!

thanks, mike

read the codes..

Check your EGR valve and your vacuum system.