I've only been driving my 1980 240 DL 2 door manual with ~200K miles a few blocks every week or two. I took it to a car wash yesterday, and was on my way to another errand, when I lost power suddenly. I was able to limp the couple blocks home, but the car still idles roughly, has no power, and makes a lots of valve clatter sounds under load.

I noticed that when I press the connector for the fuel frequency valve, the idle smooths somewhat (but not to normal), and when I push it to the side, the idle roughens or dies. This is repeatable. There's lots of vacuum lines around there, and the rubber bellow attached to the throttle body, so I'm not positive that I'm not affecting a vacuum leak when I move the frequency valve connector.

Also, I mentioned the car wash because I'm wondering if water might be a factor (the problem occurred a few blocks later). The windshield wipers often get stuck on on this car after a car wash, and I have to remove a fuse until it dries out.

Anyway, it's been a while since I did any troubleshooting on this car, so suggestions on next steps are welcome. Thanks!