Service Engine Light On problems of the 2009 Nissan Versa

My service engine soon light came on so I dropped by advanced auto parts to have them pull the code. It read as cylinder 4 misfire. I took it in to mcgee auto to have a detailed diagnostic, which indicated that I had a bad coil on one of my spark plugs. I had four spark plugs replaced, an ignition coil changed, and intake manifold resealed; however, after leaving and getting a few miles up the road the ses light came on again. I stopped at another advanced auto to have the code pulled and again it read as a cylinder 4 misfire. I contacted the repair shop and was asked to bring the car back in. They did another full work up and again found everything to be fine. After leaving the shop again the light came on a few miles up the road. This happened repeatedly, and every time they would shut the light off it came back on and remained on. In March under new management, I returned to mcgee auto and they took another look. After posting my symptoms into the computer they noticed that my original plugs had been replaced with aftermarket plugs. They replaced all four plugs and coil, and did something with the fuel injection at no additional cost to me. After leaving the shop a couple miles up the road, the light came on again. I took the car back in on Monday, 3/18. Further research entailed a compression test. Cylinders 1 through 3 had 130% compression, but cylinder 4 only had 70% compression. I was advised that the issue is an engine problem and without tearing it down they are unable to identify the exact cause, but it could have something to do with the piston in cylinder 4. In contacting Nissan, they found that my warranty coverage is for 60,000 miles and unfortunately I was at 66,000. When asking what this really means I was told that I will likely need a new engine or a new car because it would be costly to tear down the engine to find the problem.