I have a 93 suburban that has started backfiring during load. It only does it during acceleration or going up hills. It has also started surging at idle and misses frequently at idle and road speed. The Tach is also jumping a lot but the engine speed obviously is not changing as much.
This is a 93 with 203K miles and a 5.7l engine.
I have replaced the distributor, cap, rotor button, wires, plugs, TPS, MAP sensor, EGR valve,Temp sensor and O2 sensor. I am at a loss as what it could be. I have tried using starter fluid to look for vacuum leaks and did not see any engine reaction anywhere.
Any help would be appreciated.
