I have been living with a rough idle and pretty gnarly harmonics for awhile (certain RPMs would cause the car to vibrate from the cabin). I just thought she was running rough but when I drove up to a car meet, my buddy said it sounded like a cylinder was off and I was running on 3 cylinders!
So later that day, I cranked her up, we pulled the ignition wire for cylinder 1/coil 1 (closest to the radiator, do I have the # right?), and it made no difference to how it ran. Wild.
A few baseline items: Its an e30 m42. I have a coil on plug set up. I have newly rebuilt orange top bosch injectors.
So I limped home in shame and started diagnostics. Here is what I have found.
1) I removed the coil and kept the spark in. Cranked the engine and she's sparking.
2) I checked compression and I have 130 psi in cylinder 1. Not great. Not bad (I think). Should be enough to fire (a little concerning however).
3) I checked the continuity from each coil wire to each ECU pin as prescribed below. All match.
Coil #1 is DME connector pin 25.
Coil #2 is DME connector pin 52.
Coil #3 is DME connector pin 24.
Coil #4 is DME connector pin 51.
4) I pulled out my stethoscope and I can hear each injector ticking. Some sound slightly different than others, but each have a distinct ticking sound, particularly injector 1.
So Im not sure where to go from here. How can I test that Im getting fuel down the cylinder? What else can I do?