Loud backfire

Welcome to 2CarPros.

Most times, a backfire from the exhaust is caused by a rich fuel mixture to the engine. That can be caused by a fuel pressure issue or a bad injector. It can also be caused by a misfire related to the ignition system. However, in that case you will feel an engine miss.

Take a look through this link first.

https://www.2carpros.com/articles/engine-backfires-while-running

Now the first thing I suggest is to check fuel pump pressure to the engine. Here is a link that shows in general how to check fuel pressure:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Here are the directions specific to your vehicle for testing fuel pressure. In the first pic below, I highlighted the place where the fuel pressure gauge will attach. I realize most people don't own one, but most parts stores will lend you one. Also, the manufacturer's specs for pressure are listed in the directions.

If you find the fuel pressure is correct, then I need you to scan the computer for diagnostic trouble codes. This vehicle has an OBD1 system, which means you can get the codes without a scanner. All you will need is a paper clip or jumper wire. Here are the directions for retrieving codes:

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

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1994 Oldsmobile Truck Bravada V6-262 4.3L VIN W CPI
Fuel System Pressure Test
FUEL SYSTEM PRESSURE TEST
Central Multiport Fuel Injection (CMFI)

pic 1

Fuel Supply System CMFI

Pic 2

PROCEDURE
- Turn engine "OFF" and relieve system pressure. Refer to Fuel Pressure Release Procedure.
- Connect the fuel pressure gauge to the pressure connection. Wrap a shop towel around the fitting while connecting the gauge to avoid spillage.
- "START" engine and observe fuel pressure reading. It should be 380-420 kPa (55-61 psi).
- Turn engine "OFF" and relieve fuel pressure.
- Remove fuel pressure gauge.
- Reinstall fuel pressure connection cap.
- "START" engine and check for fuel leaks.

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Let me know what you find or if you have other questions.

Take care,
Joe