I have an 89' Suburban with a rebuilt 350 tbi. The motor is drinking anti-freeze, but that is another problem. The issue here is that the motor (especially when cold) surges and idles up and down to the point of almost stalling when being driven. It seams to run fine in park, idles short of 1k. When I drop into drive it drops to about 600. When I take off from a stand still when running like this it feels at some point like it "clears out" and runs better. I does this when ever it wants and is shortening my life one day at a time.
I have replaced:
Fuel filter
EGR
EGR control
PCV
All rubber lines
Reset timing.
I have no engine light or trouble codes popping up to help me. I am suspecting the injection controls or injectors. But as a thought could the coolant burning in the motor have anything to do with it? I have no coolant in the oil, or any spots of leaks anyware. It is being burnt in the combustion chamber.
Thanks for looking!
- Ingoldx1