Car wont start after it sits in the rain over night

I own a 2006 Chev Cobalt with 133000 kms (yes I’m Canadian). About 6 months ago after the car sat over night in the rain, it would not start that morning. It would turn over and cough and sputter for afew seconds but not stay running. I had it towed to my garage. The car sat there for a while and when the mechanic got in, it started no problem. The mechanic tried hosing down the entire area under the hood to get the car to act up, but that didn’t do anything. I took the car home and we all chalked it up as a fluk. Then a week later , after an over night in the rain, it did it again. Towed to the garage and it fixed itself by the time the mechanic got to it. This happened 3 more time ( thank goodness for CAA). They sprayed all the ignition parts with something like WD40, they even got ahold of another coil pak that I could borrow to see it that would solve the problem… it didn’t. They put it on a code reader and it read " Camshaft positioning (CMP) sensor circuit". But they ( my mechanic) told me that they just didn’t know what to do next. They recommend another mechanic, but I haven’t gone yet because I’m afraid that they will look at my car as a “cash cow”. For now, to avoid this problem, when I know it’s going to rain, I plug in the block heater, and put a desk lamp with a 40 watt bulb under the hood, then bungy down a tarp over the hood after I close it. I would like to point out that if I go to work and the car gets rained on all day (9-5) it will still start. It seems like the car has to soak in the moisture first.
Any thoughts?

I would look at the CMP connector, sometimes moisture can get into the connector.

I recently had my Cobalt in to another mechanic. He did a computer scan and the code for the Camshaft positioning (CMP) sensor circuit" was there ofcourse. He checked under the hood, and guess what ? There is no CMP. So no possibility of moisture getting into a connector. Apparently my model year and older don’t have one. So why would the computer have this code? The mechanic did replace another sensor.He checked the conections and found them to be in good shape. But it hasn’t rained much to see if the car is fixed yet. Anyone out there have any idea whats , what?

You need to start with the actual code (P1234 or whatever it actually is).

Indeed - find out the exact code. The codes aren’t about parts. This may have been a code that a lot people assume is related to cam sensor function. There are hundreds and hundreds of codes. So find out what it is and post it.

I’m not sure you should be trusting this mechanic either way. RockAuto will be happy to sell you a camshaft position sensor for $48.79 + s&h.

Hopefully someone at least took a gander and the CRANK position sensor. Both of these should be checked out…once you find a shop that can find your cam sensor.