Can anyone tell/reference info on the vacuum advance/retard aspects of the Starting Valve, Thermal Time Line Switch, Supplemental Air Valve, Cooling Temp Sensor, & Switch-Over Valve/relay, for the above mentioned car? It goes from purr to cough & back & I suspect the ingition timing-vacuum continuum.
I would suspect the points in the distributor... much more common problem.
Sorry, failed to mention Petronix electronic ignition.
Before you mess with that have you verified the injection rack moves freely?
Injection rack on a 72 280SEL 4.5?!?
That engine has EFI......
I would suspect the cold start valve first. When it idles rough, clamp off the hose at the cold start valve. If it smoothens out, replace the cold start valve.
If it does not help, I would remove the distributor and take a look at the trigger points. They may have oil on them......
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