1995 Chevy Silverado 166,000 miles 5.7 two wheel drive backfires through throttlebody when under a load or getting upto highway speeds. Especially after short periods in slower traffic. I have replaced cap, rotor, plug wires, plugs, fuel filter, and coolant temp sensor. I was told it could be a part in the distributer slipping and causing the timing to be way off.
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.
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Thanks Dave, I'll see if I can get a scan tool or tell my mechanic to try it. The problem is sporatic and has happened more recently since the weather has warmed up.
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