[david-b]

Welcome to AF.

Firstly do a compression test. Testers are cheap and can be rented from most auto parts stores for really cheap. The compression test will tell a lot about a motor.

I would also drain the oil and check to see if coolant is in there. If so, headgasket is shot.

Does the car smoke at all out the tailpipe?

Make sure it doesn't overheat as it will start warping the head (if not done already) and you will have a bigger, more expensive problem then.