Greetings:

I love my 850, simple problems till now I am guessing.

My car runs very rough at idle, there is a sputtering noise from the muffler and the car shakes and vibrates a lot. The check engine light is on and also flashes for a while. The service light is on for a few minutes after startup. My fuel economy seems (my odometer is broke) to be terrible. Like 12 mpg or so, all of this happened with the shuttering, vibrating car. I replaced plugs, cap and rotor - no change.

Local amatuers say I need my head rebuilt and they will do it for 550-700. They said 2 or 3 of the cylinders have little to no complression. They say my valves need to be replaced. They have done simple work for me in the past (brakes and muffler), not sure if I am ready to have them rebuild the head.

Do my symptoms match their daignosis?

Could it be anything else?

I did leave my gas cap off and fuel door open one night several weeks before the shuttering car and that night it rained. I put isopropyl in tank and also injector cleaner and high octane gas. No change. I have heard I might try a bit of transmission fluid in gas...any thoughts?

Thanks