2008 Mercury Mountaineer, 4.0 SOHC

Diagnosing this issue has kicked my but! Always #2 cylinder, mostly under 1200 rpm's but occasionally cruising at highway speed in overdrive. Originally happened more while cruising then morphed to mostly under 1200 rpm's.

I had eliminated a dropped valve seat, broken valve spring or burned valve because there was absolutely ZERO noise and I had good compression. I replaced several sensors, intake gaskets, and several other failed attempts at resolving the issue. Including tracing a no pulse signal at the injector to the PCM. This made me wonder if the injector driver was bad for #2 cylinder in the PCM. Then someone enlightened me about the PCM purposefully shutting the injector off so raw fuel is not pumped through the cylinder when is not firing. I finally had to step away from it last week to clear my head and do more research.

I started over! The misfire was due to a lean condition so I kept thinking either fuel is not getting to the cylinder or to much air is getting to the cylinder via a leak. I had already tested the injector, it works, and I had tested for air leaks extensively, none. Compression test was good. Vacuum test was good, while misfiring, no back pressure so the intake valve was seating correctly but was it opening? I pressurized the cylinder with air and turned the motor slowly to verify the valves were opening and closing and the cylinder would hold pressure. ALL PASSED! I performed several other test including removing the valve cover to inspect the valve train, with no success and gave up for the night. At least I could eliminate Burned valves, broken valve seat, broken or weak valve springs, failed lash adjusters, etc.

 

More research! Watched a video where the guy holds a piece of paper next to the exhaust to test for bad exhaust valves. WTF! How easy can you make it! If the paper gets sucked back toward the exhaust then the exhaust valves are not seating on the down stroke. I tried it and by chance the engine was normal so it was pushing the paper away. Then, it went into misfire mode and started working the paper back and forth. Meaning that ****ing #2 exhaust valve was randomly sticking open during the intake stroke. The air to fuel ratio is way to high, LEAN, causing a misfire. After a few cycles of this the PCM shuts that injector down.

AT LEAST THATS MY STORY AND I'M STICKING WITH IT! FOR NOW!

All well and good but how do I unstick a sticky injector?

More research!

 

Still seems like there would be some noise due to the lack of tension on the cam follower!