Kind of a long story, but I recently did the head gasket in my 2012 prius. The headgasket showed signs of being compromised for cylinder #3 where coolant was getting in. The head gasket visually showed signed it was compromised at cylinder #3. Everything is reassembled, but it makes a weird clunk sound. Unplugging different coils led to the issue being isolated to cylinder 4. The engine runs fine if the coil for cylinder 4 is unplugged. Prior to the repair, cylinder #4 did not have any issues. Below is a list of stuff I've tried so far - - compression test, all cylinders are 170psi + - swapping coils, sparkplugs, injectors with other cylinders to #4. - reset the computer by unplugging the battery - checked the timing. The timing marks line up for the two cams and cylinder 1 is in in the upmost position by putting a stick down the cylinder to measure - Put a camera down all cylinders and the intake valve section, they seem normal - Turned the crankshaft by hand and it rotates fine without abnormal sounds - When the engine cranks when the electric motor runs, there are no sounds, appears to be normal. There are a number of CEL codes - P0031 - Heated o2 sensor P0102 - maf sensor P011 - intake air sensor P0351, P0352, P0353, P0354 - coils were unplugged/removed for the compression test P0403 - EGR The CEL codes appear to be from unplugging and re-plugging various sensors/devices. Pressing the gas pedal while in park does not rev the engine. Any thoughts?
