Recently has this problem after using a hose 50 # pressure to clean after a snow ride. Acted like it was running on 1 cylinder. Tried heat/cool cycles over a weeks time and finally took it to the shop where at first it ran fine and then did the same thing after sitting outside. It corrected itself again while there before they hooked up the computer. I have the car back and am afraid it can recur anytime. Any thoughts?