Erratic Idle/Surging: XJ-12

[pgrant@balink.com (PHILIP B. GRANT)]

     Background
     
     1. 1978 XJ-12 78k miles. Purchased at auction (no service records).
     
     2. Symptoms: No start/very difficult start <50 F. When started surging 
     from 750/1000 rpm. Very rough idle.
     
     
     3. Recent work:[all by yours truly, Mr. Badwrench]. New cap, wire set, 
     rotor and pick-up. Replaced faulty auxillary air valve.Replaced 
     throttle position switch. New Bosch plat. plugs [gapped at .35.]. New 
     battery. Recently puchased VOM and have checked: coil; injectors; 
     manifold pressure sensor.
     
     
     Questions:
     
     1. What is the most likely source of the 1000RPM wild surge? How can I 
     best diagnose?
     
     2. On a recent (warm Day) start up I noticed the drivers side cat 
     became cherry red after 7-8 min. What could cause? I assume this is 
     not normal.
     
     3. Other than a voltage drop test is there some simple way I can 
     eliminate the starter as marginal/bad re: no-start/slow crank on cold 
     days.
     
     4. I suspect the thermtime switch and cold start unit as possible 
     trouble makers. Are these high failure items...likely suspects..?
     
     
     THanks to any and all who respond. I'm eager to drive the beast but so 
     far its been a blizzard of fixes with marginal progress.
     
     Best regards,
     
     Phil Grant
     Loudoun County, VA US

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