My 1990 sillhouette kills at a stop sign

Sputtering is usually a sign of having a fuel issue. You need to hook a fuel pressure gauge to the fuel rail and confirm that you have at least 40# of pressure at the rail.

check your idler control valve(motor) this valve controls idler an low speed it is located on the throttle body

dirty throttle body, check air filter.

egr valve is bad

I had the same problem with the same model . If it is 3.4 crank balancer shaft is broken.

Try pulling the vacuum line off of the EGR valve when the engine is warm and starts to sputter. If it runs good cold and then dies when warm and won't start again until the engine cools it is most likely a bad or sticking EGR valve. Try the procedure to confirm it is the EGR. You can check the internet for location and an image of the EGR valve for your specific car. Please rate me on this answer.

Have you checked fuel pressure? 12 psi?

try unplugging the one plug in front of trans it has 2 or 3 wires in it . its below the battery it is the lockup solinoid and they go bad and keep the trans in lockup mode and will do what your saying.

You may have a problem with idle speed control motor or ETC as GM calles it. here is a photo and a price from rockauto.com.
STANDARD MOTOR PRODUCTS Part # SA4
Motor Assembly $110.99

check the fuel pressure and the timing.. check the vac lines on the car.. good luck..

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