I would rebuild the TBI with a kit. The fuel pressure spring may be weak and allowing too much fuel at idle. What I did was get one that was decent from a junk yard and disassemble it. you will have to heat the throttle body screws with a small propane torch to soften the locktite on the butterflies. Take it to a local engine shop and have all the parts cold tanked overnight; then bead blasted. Get a rebuild kit from a local Napa, Advanced Auto, etc. If you can afford it get new blueprinted injectors. Then swap out your old one with the rebuilt one so you don't have any downtime. I've rebuilt several and they can be done on the cheap and work great. Also make sure your timing is stock. I believe it is 0 at TDC.
I have an '88 S10 4WD 4.3L It is no longer stock as I have rebuilt the engine and added an Edelbrock Performer RPM cam and intake along with a modified TBI I bought on ebay along with a TBI spacer, accel coil, hedman headers and higher volume fuel pump. I also have a TBIchips custom chip. It is probably close to 300HP and 340lb/ft torque. I just put in a stage 2 transmission with higher shift points and hard shifts. I'm working on a new posi rearend with disc brakes and 3.73 gears to replace the stock limited slip drum 3.08 rearend. I'm still looking for some reasonable front 3.73 gears.
Last edited by Artster; 10-11-2011 at 11:40 AM.