I have a 89 iroc -z with a 350 tpi. the motor was alwas shakey when idling but now when in closed loop the idle varies between 500 and sticks at 1200 and when your just putting around it wants to stall.
heres what i've checked
new fuel pump
new fuel filter
new plugs, wires
new coil and module
new tps and iac adjusted properly
timming set to +8
checked for vacume leaks
scanner shows that when the idle sticks at 1200 the iac steps go way up and the tps goes from like .54 to .62 but nothings binding or stuck. I think my injectors could need cleaned and that might be why the motor shakes. I got the motor from a wreaked 91 vette in a junk yard so the injectors prob need attention but now this new prob sounds electrical. what you think??