My car's engine light is on and the car is shaking. What is wrong? on 2000 Mazda 626

This just started after I put some gas in it on yesterday. Steam is also coming from my car. I put water in it to make sure the heat gauge stays down. I also notice this: when I would turn the vent to heat I would not see the steam and when I would turn it to cold, I would see the steam. yep. If there be any old time mechanics out there, please give me your advice.

Asked by for the 2000 Mazda 626
1 answer 1 comment
Either bad gas, but if you are getting steam and running hot, you probably have a blown head gasket.
Hey thats what I have been told. Can you give me an estimate? How much would it take to buy a head gasket and to put one in?