Almost everytime I go through an automatic wash near the end of the wash cycle my car starts shaking a little bit and feels like it is going to shut off. This is the only time my car does this, what causes this and is it normal?

 

Moisture could be getting into your ignition wires and shorting out your spark plug(s). Probably a good idea to change the wires and possibly the spark plugs too.

 

I just had a whole tune up with spark plugs, wires, new capicator coils, etc. It has done this before I replaced them also.

 

It also sounds like it could be a ground problem. Taking your car to the car wash really shouldn't affect any of the plug wires since there is no chance of them getting wet, but a ground wire certainly could get wet especially if it's a car wash that uses the underbody wash.

 

How does undercarriage washes work? The only time I get them is after a huge snowstorm when there is a lot of salt on the road. But I always had a concern of things getting wet that aren't supposed to get wet.

 

As far as I understand it, there are just jets that spray the undercarriage. They're in the floor of the car wash.