Quote:
Originally Posted by FREE100KSECRET
Curious, I had first a PO303 code and PO300 which was occasional, put fuel injector cleaner and it seemed to help, but came back, and no same codes on 2.3.4 cylinder, So what would cause this suddenly, checked connections and harnesses, ordered injector when #3 acted up, but I feel it is something else. Any ideas?
Thanks,
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First off, the codes you're seeing probably have zeros where you are typing the letter "O." The letter O is wrong. The zero is right. So when you google it, if you use the letter O, you'll be finding "answers" from someone who at the least made that mistake, and may be making others as well. Google with the digit zero, and you'll be starting from a better place.
So google for P0302, not PO302. And sure, you might find anecdotal info about someone who had a particular component failure, it gave a P0302 code, they read it and posted it as PO302, and before you know it, it becomes internet fact that a PO302 means that particular component is bad. But like most internet facts, that would be wrong.
My understanding from cars in general (including BMWs), is that a P030# code indicates a misfire on cylinder number #. Simple as that. P0300 is a general misfire code meaning that one or more cylinders is misfiring. A bunch of the comments so far in this thread saying otherwise do directly contradict what I'm saying here.
The misfire codes themselves do not attempt to tell you what is causing the misfires, just that misfires are occurring. More specifically, misfires are typically detected by measuring the timing of the crankshaft rotation very accurately (for misfire detection purposes). The CPS or crankshaft position sensor does this.
If a misfire occurs, the piston will not see as much combustion pressure as it should, so the torque on the crankshaft will be a little less, so the time for crank rotation through that cylinder's angle will be a little longer, which the CPS will measure. If that is found to happen reliably enough, the ECU will declare a misfire on a particular cylinder, maybe turn on the Service Engine Soon light, set codes, go to a limp mode, etc.
At that point, you may be on your own to find what is causing the misfire(s) - there may or may not be other codes to guide you (e.g., a lean mixture code). Another complicating factor is that the detection is sometimes not accurate about isolating which cylinder is bad. Accuracy seems to vary with engine types - I'm not sure how accurate it is on these M54s. So you can have a single cylinder problem (for example a flaky ignition coil on #2) that may result in crank rotation speed variations that will cause misfire codes on multiple cylinders, even though the actual problem is only on that #2. So if your problem started with a single P030# code, and now you have a few of them, it could just be that your one isolated problem has become worse rather than that it is spreading.
This is all general stuff. Sorry, I have no "answer" for you.