Seafoam it.



J/K.


Double check your timing. Is the stock valvetrain in the car? Erratic idle can be caused by a number of things, start with your IAC. Unplug it and see if the idle smooths out. (You'll have to play around with set screw on the TB)

 

Talk about problems.. When I first got my 90 it ran great.. but a little rough. Replaced the wires and plugs and the motor was so quiet and smooth. Fast forward to sitting for weeks while I was cleaning out the interior, painting parts, repairing rust etc, the car quit starting. Replaced the starter, solenoid, battery, alternator wiring, put new grounds in and still nothing. At this point I'm pissed. So after days of talking with mechanic friends, they are all confused and I couldn't find ANYTHING online about it. Well, come to find out there is a clutch safety switch I had no clue about.... wiggled the wires and she fired right up. woohoo!!

Anyway

Last night after fixing my door harness, shes doing this exact same thing the OP is having issues with. So I'm curious if he figures out whats going on.

I had a 87 T-Top that was a complete POS body wise, but I never had one problem with engine, wiring or these other little gremlins.

 

having/had or figured it out.. complete fail on my part for not looking at the date.