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EGR valve... over time my '93 K1500 5.7L engine started coughing/stuttering/surging especially at low idle. I changed spark plugs and wires, distributor cap and rotor, O2 sensor, map sensor, fuel pump, rebuilt the TBI, and fixed the timing, still the engine ran rough.
Then I accidentally broke the brittle EGR tube that connects the valve to the solenoid as shown in the picture - the problem went away, no more engine stutters. Funny breaking something seemed to fix the problem. I repaired the tube and the engine stutters returned, so I put the broken tube back on and let it be. I assume my EGR valve and/or EGR solenoid are causing problems, or maybe its something else.
Two stupid questions: 1) what does this EGR valve and solenoid do for me - are they important? and 2) should I replace them or just leave it alone with the broken tube? Appreciate any insight.