Car usually cranks but will stall out when I let off the gas sometimes backfires?

Hi,

This can be caused by a few things. First, do you ever notice gray smoke from the exhaust or a strong exhaust odor?

Next, a backfire can be caused by a rich or lean fuel mixture. Also, if there is a vacuum leak, it can cause a lean fuel mixture and cause it to stall. So, first, check to see if there are any leaks. Here is a link that explains how it's done.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

There is also a component located on the throttle body called an idle air control valve (IAC). If that malfunctions or needs service, it also can prevent the engine from idling. Actually, when you remove your foot from the throttle, the engine loses the air needed to run. Here is a link that explains how one is serviced.

https://www.2carpros.com/articles/idle-air-control-valve-service

If you look at the pic below, I circled the IAC.

One last suggestion, let's check to see if there are any diagnostic trouble codes. Here is a link that explains how to retrieve them on this vehicle. You don't need a scan tool. All you need is a short jumper wire or even a paper clip. Follow the directions in this link and let me know if any codes are stored and what they are:

https://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method

Let me know what you find.

Take care,

joe

See pic below.