What is making my 99 Silverado Z-71 Idle fluctuate at idle and backfire when I try to accellerate hard?
Answers:
i don't really know your model, so i don't know if it's a gasoline or diesel engine, but it seems to me that you might be having an ignition problem (if gasoline) or the presence of impurities in fuel.
usually backfire is generated by unburned fuel that reaches the hot exhaust, so probably, there is a problem with your spark plugs or the unit that controls them (don't know the English term).
I'd examine the chromaton. If the lych pin is neuter then try a cotter, if not then aspirate.
Sounds like you have a problem with the intake. Try getting the engine and choke retuned. Also check for any clogs in the intake and the spark plug condition. Backfiring is usually caused by incorrect ignition timing so you can check on this too. Lastly, you can also change to "hotter" spark plugs (plugs with a lower heat rating) to compensate for the colder weather.
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