It was running fine, then almost home from work it started backfiring. Doesn't matter if you let up on the gas peddle or give it more gas, even parked it for 30-40 minutes and when I went and restarted it it backfired then as well.
I know there are a lot of solutions here but I would concentrate on a couple of known issues for the 99 4.3l engine. Remove the distributor cap and rotor, check the reluctor wheel under the rotor and make sure it is not loose on the distributor shaft. The other issue is a worn distributor gear, you will notice a lot of freeplay when you try rotating the distributor rotor back and forth.
Last but not least, spray the inside of the distributor cap, the rotor and the inside of the distributor, this will remove and prevent moisture build up causing the backfire issue you are experiencing...
Good luck.
Sorry, spray the inside of the distributor cap with WD-40, soak it good.
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Hello, faulty fuel injec tor it's leaking GB...stewbison
I would say you have timing problem, worn timing chain or gears, what is the mileage?
SOUND LIKE LEAN FUEL MISFIRE COULD HAVE CLOGGED FUEL INJECTOR,IF THIS HAPPEN ALL AT ONCE COULD HAVE CONTAMINATED FUEL.IF ALL IS GOOD YOU COULD HAVE WORN VALVES, INTAKE VACUUM LEAK AT VACUUM HOSES OR VACUUM LEAK AT FUEL INJECTORS,COULD HAVE BAD SPARK PLUGS AND WIRES, MAKE SURE SPARK PLUGS WIRES IS NOT CROSSED UP.REPLACE DISTRIBUTOR CAP AND ROTOR.IF EVERY THING BEEN REPLACED YOUR IGNITION TIMING OR VALVE TIMING OFF.BUT CHECK FUEL SYSTEM YOU COULD HAVE PLUGGED FUEL FILTER.VERY WEAK FUEL PUMP LOW FUEL PRESSURE.
The only thing that will cause a backfire is unburnt fuel entering the exhaust. This is caused by faulty combustion. This is directly related to the spark or ignition system. Start simple by removing one lead at a time and free run the engine to see if you can locate which lead or plug is faulty. If this doesnt reap a result then the fault is either in the distributor or the ignition coil. Take the cover off the dizzy and make sure the cap and rotor button are not corroded, if they are dirty give them a rub with emery paper and coat liberally with CRC/WD40/Startyabastard. If the dizzy is worn internally then you will have to get it rebuilt as these are a specialty item(read as '**** fiddly'). Hopefully this will help. Get back to me if you have looked at all these thinhs and still have trouble. Cheers.
Hello, All I have read from other Experts can be true. Try opening the hood in a dark area without the headlights on and see if you can see Spark jumping from the wires on the engine when it is running. A sparkplug wire may have burned off or has fallen off and is shorting.
Hi Frank, Get it scanned first and find out if there are any trouble codes. Are you getting an actual back fire or is it a misfire? With a backfire an explosion is set off in either the exhaust or intake manifold. If it is backfiring through the intake it can cause a fire! You've been warned! If it's a misfire the engine will run rough. If the roughness is regular following a beat, the problem will be related to one particular cylinder. If it's irregular (sort of jumpy and uneven) the fault will be somewhere common to all cylinders. As one of my friends above have advised, have a scan carried out and see if that gives the fault. If you can be more explicit in describing the fault we can be of more help. Regards Johngee10
Backfires are useualy cai used by a build up of fumes in the exaust system, which can be caused by several things,ie, faulty ignition,bad plugs,timing belt wear or carbarator have it checked out by a mechanic! as backfireing can also damage the exaust system!!
Also cam sensors are known for this and also cat converter could be getting clogged
SOURCE: What would make my 1999 Chevy Blazer 4x4 with a 4.3L Vortec engine suddenly start backfiring?
bad spark plugs, cam sensor or timing, or you could have clogged cat canverter
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Hello! there is a list of causes for a backfire...Lets try and narrow it down,,,Is the engine trouble light on ? if so, can you pull a code? Is the engine in a fairly high state of tune; Plugs, filters, wires? Any recent activity with the timing chain?...Send a comment to Guru...Saailer
Is the back fire in the exhaust(indicating unburned fuel igniting in the exhaust) or is it backfiring through the throttle body(indicating lean condition, or faulty valve or ignition timing?
I'm sorry folks, but two weeks ago, I asked if it was backfiring through the exhaust, or through the intake, and there has been no answer. Unless we know that, aren't we wasting our time?
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