after a long road trip with cruise control at 80mph, suddenly cel started blinking when i was climbing a small hill. i immediately stopped the car, popped the hood open, everything seemed ok so i restarted it, it was chugging like crazy, but it worked. obd reader and bimmerlink states misfire in cylinder 4. nothing else.

here comes the stupid part, i kept driving till i get home (about hundred miles), thinking it's just a dirty injector or coil or plug. car seemed fine over 3k rpm so i lowered a gear and cruised around that rpm range.

next day, i removed plugs, 4 was just straight up black, others looked ok. i dunno what i was thinking but i swapped plugs and coils, tried to start to car, it started and died immediately.

i called a tow and bring the car to a reputable independent service, they tried starting it, it started again just to die immediately. they removed plugs and now there are 2 plugs extremely black, one is from the 3rd (which i swapped with 4th the day before) and one is from the first, which was at mint condition before i tried starting it!!!

compression test came next: no compression at all in 1 and 4. wtf? while 2 and 3 pushing 160psi.

i have a very bad feeling about this guys. i'll keep you guys posted.

 

first update: upon removing the head, valves in 1 and 4 is bent. cylinders and walls look good, new set of valves seems like is all i need. it seems like the timing job my other guy did 10k miles prior was bad (my long term fuel trim was around -10 percent after the timing job indicating rich condition, i thought it was just a bad injector or something like that), after a power surge, timing skipped a tooth or two and valves contacted pistons. at least that's what they are telling me. i'll keep you guys posted for future references.

 

 

4th piston seems shot :( and that chip on the 3rd cyl wall doesn't look good to me either. what dou you guys think?