Strange issue with my blazer. 89 4.3 4x4.

When starting cold, it rarely idles for more than 30-45 seconds before dying. I can give it the slightest amount of throttle for about 60 seconds or so to keep the revs up, and then let go and let it warm up.
When driving, if it isn’t fully warmed up, the revs are very rough and it has little power. This usually only happens for about a block and then it starts running better but not perfectly. Even once fully warm, idle sometimes fluctuates slightly and power sometimes dips out (acts like it isn’t getting gas)

Check engine light goes on and off. Sometimes it will stay on for 5-10 minutes, sometimes less than a minute. Occasionally it runs as if it had no issues and the check engine light is usually off during this. I have tried getting an engine code over 10 times now, and every time, no matter if the light is on or off before trying, as soon as I Bridge the obd connector to get into diagnostic mode, it always only gives me code 12 (which is no error just showing we’re in diagnostic mode). It’s frustrating cause I want to know what is causing the light when it does come on!

Anyone have experience with this? Thanks for reading,

Brad

 

I should also mention, I just cleaned the EGR valve, and did a seafood treatment. Poured some slowly into the tbi, let the brake booster vacuum line suck some up, and put a full 20oz can into 20 gallons of gas, and that really seemed to help. Maybe I should do more on the engine side?
i also just readiusted and double checked timing