Engine Performance problem
1990 GMC Sierra V8 Two Wheel Drive Automatic 200000 miles
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Original problem was that my truck wouldn't start. In narrowing down the problem, replaced the fuel pump, rotor, battery, ignition coil, tested the alternator (which is good), and found the problem to be the ignition module. Truck started and ran fine for a few days but then started running rough, it started pulsing RPM's randomly and now it dies usually when it's in the lower RPM's. Especially at an idle. Whats going on? It has a carureted engine FYI and I had replaced the fuel filter a couple years back so not sure if that would be it. Not sure how often those go out. It's been a while since my last tune up, wondered if it would be plugs and wires maybe?

Try the plugs/ wires and check the idle air control valve/throttle position sensor/EGR and PCV valves.