My '87190 E 2.3 cuts out when the engines gets hot.It then only starts after it cools down (15or 20min).When it happened last week, I was just putting up the hood when an off-duty Mercedes Road Side Service truck pulled up. He quickly identified that I was getting no spark, but couldn't tell the exact cause. I Figured it might be the coil,and checked it with a Volt/Ohm meter. It didn't give me the specified #s so I changed it. The problem however persists. I read a few threads about the OVP, so I when out to take a look. Turns out that mine is missing! What affects will a missing OVP cause on my car? Could this be my problem?
Thanks for any input.

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1987 190E 2.3L (Daily Driver)
1985 VW Scirocco (Mint-Summer)