Hi, this is Bo, an auto expert on RepairPal's Car Genius team!
A '93 'Vette idling like it's got a bad case of the jitters instead of that classic rumble? That's no fun. The MAP sensor is a key player, telling the engine's computer about engine load. If it's not reporting for duty, things can get rough.
When you say your multimeter test showed 'nothing,' it's a bit vague, like a weather forecast that just says 'weather.' What were you probing? MAP sensors usually have three wires: a 5-volt reference from the computer, a ground, and a signal wire back to the computer. If you're not seeing that 5V reference, or the ground connection is MIA, then the MAP sensor can't do its job, even if it's perfectly fine. If those are good, the signal wire voltage should change with engine vacuum – higher with key-on-engine-off (around 4.5-5V) and lower at idle (1-1.5V).
If you're truly getting 'nothing' on all pins, double-check your multimeter settings and connections. Are you on DC volts? Making good contact? If the 5V supply is missing, the problem might be upstream. But if the supply and ground are good and the signal wire is flat-lining or not responding, then yes, your MAP sensor might have decided to take an early retirement. A bad MAP is a classic cause for a rough idle, but don't forget its rowdy friends like vacuum leaks or ignition system hiccups.
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