BMW M20 Intermittent Miss, Crankshaft Position Sensor, 325i, 525i, 528e, E28,E30, E34
Q
car year: 1989
car model: 325i Convertible
I have an 89 325i convertible and it has been acting up since I bought it 6 months ago. I have since then put about $3000 into trying to make it run right and look good. The problem I’m having is; the CHECK ENGINE light comes on when it’s warmed up and idles at the same speed for 10 seconds or more, but goes out when i rev the engine. Also, it has one heck of a cutting out problem, on the road. While driving, the car runs great if I’m easy on it, unless I hit a hill. When I give it about half throttle, or more, it will cut off for about a second and then come back on and if I give slightly less gas it’s OK. The problem is consistent, but it varies in how much throttle it takes to cut out.
Now for the list of new parts; I replaced the O2 sensor, Air Flow Meter, plugs, wires, cap, rotor, timing belt, fuel filter, took the injectors out and cleaned them (which weren’t dirty), fuel pump, fuel pressure reg. and maybe something else I’m forgetting. The same code keeps comming up as; O2 sensor exeeding its limits. What else could be causing this? Anything at all would be greatly appretiated. Thank you so much and I look foward to hearing from you.
A
With the description of your symptoms AND the list of parts that you’ve replaced, I would consider that you may have a failing crankshaft position sensor (this would apply to the 325i models through 91, 92-325ic, 88 325e and 528e and the 89-90 525i). The sensors can have problems where the harness wiring goes into the sensor itself or the harness plug. Additionally, the windings in the sensor head can break-down. This will often result in intermittent engine missing or problems under acceleration vs steady-state running.
The oxygen sensor fault code could be a result of the sensor picking up unburned fuel when the engine is running poorly.
Click below for crankshaft position sensor:
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I have a 1988 325i with this same problem. I have changed the fuel filter, fuel hoses, vacuum hoses, spark plugs, coolant temp. sensor. I have checked fuel pressure, compression, TPS, Mass air flow sensor. Everything checks out ok. I am a mechanic and have considered the crank position sensor, but have not replaced it yet. I just finished another build and like my BMW was getting an O2 sensor trouble code. After replacing the entire exhaust system the code went away. I believe my BMW is in desperate need of a new exhaust system as well. I plan on doing this in the next week. I have a feeling that the cat. is burned up, and my sluggish acceleration, surging, and o2 code will go away. I will keep you posted with the results. I still plan on changing out the crank position sensor for good measure, however I will do so after the exhaust has been replaced.