I have a 1987 Chevy K5 Blazer the engine idles and runs rough and idles down very low when stopped, have installed new plugs wires distributor coil new torque conv fuel pump fuel filter, any help greatly appreciated.

 

Got me stumped on doing research. Some years had carbs, and doing research shows tune port injection. More info when you post is better on what you have. Carb or fuel injection? Thinking a carb, quadra-jet.

1st off, if the quad. On the side of the carb is a vacume choke pull off. When it's running ruff and the idle is down. Is the choke plate, warmed up. Verticle? Do you get the fast idle when cold? And everything seems ok, with the fast idle? That plate, if tipped when warmed up. Can make it rich. Yuking up idle.

Other thing I ran into on a quad. The choke linkage gets gunga'd up on the pass side of the carb. Stepping plate sticks. Look for it to see if it's free. Won't let the choke pull off when warmed up. PB blaster is a good thing.

They have a ballast resister, small white block that goes bad. Mounted on the manifold, close to the carb. It provides volts to the heater inside the electronic choke pull off. They also go bad.

Kinda long and short. You didn't complain about cold start or running. Guessing. Warmed up issues. Look at the choke plate to see if vertical. If not. A vacume can pull off is bad, or the resister or electronic choke is bad and why the plate is not vertical when warmed up.

If you have the tune port injection, another animal.

 

Burned valve is the culprit.

 

Burning a valve usually happens when the carb is running lean. Or a valve got suck on the valve guide having lack of lube. Lifter stuck? And if so, you would of heard clatter. Carbon build-up on the face of the valve. Intake or exaust?

 

Sounds like you may have an vacum leak somewhere`s.Do you have acarb or fuel injection?