I have a 83 350 chevy silverado truck is backfires when i accerlate at 30 miles an hour starts to backfire i put a new ignition coil new vaccumm advance and still does the same thing. i checked the spark plugs and wires still good new rotor and cap . I need help it is just use for work and i need to run i have to bim a ride everday because of this **** never had a problem before, the motor is a crate engine and is six yeaars i checked the timing before i put the vaccumm advane was off about 2 degrees but still did the same please help

Dave C

• 1050 Answers
• Posted on Mar 08, 2009

SOURCE: 95 Silverado backfires thruogh throttlebody

It sounds very likely that it is going lean. Could be a bad Mass airflow sensor or a fuel pump, maybe plugged injectors. The first thing to do if you can get your hands on one, is to put a scan tool on it that reads live data and go up a long steady hill while you are watching the O2 sensor voltage. It should toggle back and forth across .5V, if it remains below .5V while you drive, then you know it's not getting enough fuel. If so, check the fuel pressure to spec. If it is good, then the pump is fine and you're chasing the other two.

Harvey N Tawatao

• 3854 Answers
• Posted on Jun 06, 2009

SOURCE: Poor accerlation and backfires around 3000 rpms

There to many things that can cause this, restricted fuel flow (dirty Fuel Filter), worn rotor and cap, spark plugs and wire, dirty injectors, and timing not advancing. Let's try to get some DTC codes and hope that would narrow the problem. If there is not DTC codes then that's good that it may just be a simple tune up. Here is a link for you to retrieve the DTC codes your self. If you have the new DTC Port then your going to have to go to Auto Zone and have them pull any codes from the ECM and it's free there. Good luck and hope this helps. Keep me posted and be glad to help. http://www.troublecodes.net/GM/

SOURCE: runs good til it gets hot, then backfires and sputters

Have the catalitic converter check sounds like it may be clogged. This will cause it to choke off exhaust when it gets hot

SOURCE: After tune-up and drive couple days, the engine

May want to check your oxygen sensors to make sure they are not shot.

Dana Newcombe

• 1564 Answers
• Posted on Jan 30, 2010

SOURCE: 1990 dodge 360. Runs fine. unpredictable backfire

You want to check your timing for accuracy and then check all plug wires for burned or cracked ends. Also check the single coil tower where the coilwire connects for very small cracks. Then check the inside of the disrtibutor cap for the same small cracks. Throughout this process I'm certain you'll find the culprit. Thanks, Dana