So I'm new to this forum but I'm beyond stumped. I got my little brother a 1994 Chevy s10 blazer 4.3 with the mfi engine. When we got it we were told just the spider injector was out and it was. We swapped that and it ran good after. We took it on a test drive and it was fine we thought it was good. We took it off the freeway and when we got off we had to take it home immediately cause it was idling very off. It idles high then low and spudders and wants to die. We've been replaced the map sensor, idle air control valve, throttle position sensor, air filter, fuel filter, filled all the exhaust leaks,it seemed to run a little better but still a really bad sputter in the idol. We then took off the connection to the idle air control valve and it went right back to normal just about. We drove it around for quite a while, we then called my brother and told him he can come pick up his car because it is done. We read on another forum where a guy had a similar problem but not really close to ours where he just unplug that sensor and it fixed his problem which we thought it did with ours until he got to his house and right before he got home it died at the stoplight and then right when he pulled into the gas station. It starts right back up but it is idling very horrible . I need advice really bad so I can get this blazer out of my yard and into my brothers. Any advice helps. It is pulling the service engine soon light but we can't seem to read we're not sure why except our only thought is that We have obd1 1/2.