Engine Mechanical problem
1998 Ford Expedition V8 Four Wheel Drive Automatic 158000 miles
My truck (gas engine) just started running rough and white smoke started pooring out the tailpipe. The smoke has a strong smell of raw fuel unburned. When I drive the vehicle it pings and diesels and has a hard time picking up speed leaving a trail of white smoke behind. I took it to a shop and they said that I had low compression on two joining cylinders and that it needed a head gasket ($1700). I question for the time that they had it that they actually did a compression check. There is no codes, no coolant lose, no coolant or gas in the oil. No overheating. The radiator pressure checked ok. I checked fuel pressure on the rail, checked fuel injectors and harnesses with a fuel system tester. I am having a hard time accepting that it is a head gasket. Thanks for any help.