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Got a 2008 BM 316. Im getting multiple misfires, violent idle, hard starts, loss of power, engine light on 24/7. All on the diagnostics is multiple misfires. My mechanic started by doing a compression test. Cylinder 1 and 2 failed, 3 and 4 passed. He also did emissions test, low rpms failed, high rpms passed. He found that the fuel injector 1 was pumping way too much fuel into the cylinder, so we replaced that fuel injector. Compression seems to be good on all cylinders now. He said car runs good on high rpms but on low and idle the problem persists. He ruled out sparks, coils, injectors, sensors… he said all thats left is timing chain. He thinks there is a slack to it. The thing that I dont understand is, if a timing chain is that loose to cause misfires all the time, wouldn’t it cause low compression on a compression test? How are we getting good compression numbers, yet he thinks the timing chain is the problem?
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Not really. Just emissions test, that failed on low rpms and passed high rpms. Is it possible to be a timing chain if compression test passes on all cylinders now?
Anything is possible …
But going by your description.
Has your mechanic or yourself checked live data on both STFT & LTFT @ both idle and ~3,000 rpm?
Perhaps the MAF or MAP sensor.
Beyond that ….
I would be look for a vacuum issue, where a smoke test comes in really handy.He said my car is with paired cylinders. Meaning cylinder 1 and 2 are with one MAF sensor and 3 and 4 are with another. Since we are now getting cyl. 2 and 3 misfires, it doesnt make sense to be a MAF sensor. What exactly is a vacuum issue?
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