i have an 81 280CE thats been my daily driver for over two years. when the starter cranks the oil pressure slowly climbs from 1 bar to 2. right at 2 it stumbled and started to run for a very short time then just kept cranking.

heres my theory, i blew something up under the hood last year while installing a head unit. i think it was the WUR, or warm up regulator(i saw electric smoke). ever since, the idle has been too high and you cant adjust it when the engine is cold. so im pretty sure that needs replacing but its never left me stranded.
its been very hot recently and tonight its gotten really cold so the k jet cant compensate for such a cold temp. it worked fine last summer on cool nights, so whatever has broken has been slowly dying or is still partly alive.

how can i make sure its only this one part before i waste ALOT of money?
im up for any alternate diagnosis. i have exactly a week before i start my new job.

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