I've been having problems with my EGR system on my '88 K2500. 350TBI. this is what I've found out. the EGR valve itself is fine... disconnecting the vacuum line and pluging it into the vent on the EGR solenoid stops the surging. moving up the line, the EGR solenoid is a brand new NAPA Echlin piece that doesn't leak vacuum when the metripack connector is disconnected. back probing the metripack shows an intermittant spike of up to full system voltage (on my digital VOM... my analog is buried in storage) when you blip the throttle in park. I've not hooked up the MT-2500 to it to see if the P/N switch is registering in park or not.
my question is: other than a bad output transistor in the ECM or a wiring problem, can anything else cause the spike? (which opens the solenoid, which opens up the EGR valve, which causes jerking and stumbling)
TIA, Bret