what would cause a 1999 Chevy C3500 with the 5.7 engine to fluctuate rpm between 50 and 60 miles an hour backfire and almost stall? I've gone as far as replacing the fuel pump with a new.
Did you do the filter? Could just need a tune up or maybe a maf sensor. Is it putting out any codes?
thank you for your answer Steve, I changed the cam position sensorthe truck ran great for about 15 minutes with lots of power then act it up the same way check engine light was on rpm stop back down computer like reset itself and was backfiring , I change the cap and rotor ran smoothly not as much power but no check engine lights or rpm fluctuation so far I will know on Monday when I get to drive it further but got it past 70 mph I have yet to see if I resolved the sensor issue???
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