Chevrolet Repair: 1989 Chevy 1500 running rough, gm crate motor, intake manifold gasket

Question
I have a 1989 Chevy 1500 4.3L that runs extremely rough at idle and while accelerating. At idle, it will smooth out if I spray a little carb cleaner into the throttle body.  If I drive it, it stumbles a lot while accelerating; particularly if I give it lots of gas pedal. It takes off better if I ease into the gas gently.  Occasionally, while accelerating, it will spit back through the throttle body.  This 4.3L was a gm crate motor installed before I got the truck.  I have replaced the EGR valve with no effect.  Any help you could suggest would be appreciated.  I have even considered converting to an old style carb configuration that I can understand how to tune.

Answer
Do NOT even consider trying to convert the system back to a carb setup as you will have more problems than you can ever imagine.

If it smooths OUT spraying carb cleaner this tells me that you have a vacuum leak possibly in the intake manifold gasket, or the throttle body base gasket or some of the vacuum lines are NOT installed correctly to the various components.

Spray carb cleaner around the intake and on the numerous vacuum lines and see if the engine smooths out as this will tell you where your vacuum leak is.

Could also be a weak fuel pump.


let me know what you find out.


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