Quote:
Originally Posted by Effduration
...Real world advice from BMW and many other vehicles.
Long Term Fuel Trims are the most important value to pay attention to in addition to the engine operating temperature. Short Term Fuel Trim values are ALWAYS changing rapidly and they need to me mentally averaged. They are less of a concern or value that I pay attention to, but these do come in handy for the final analysis of a problem, usually when pinpointing bad MAF's....
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Thanks,
Effduration, for that link; I've downloaded it to my phone as a .PDF file, so I can study it awhile. Previously, I've been watching YouTube videos from "
50sKid" about testing BMW vacuum leaks via fuel trims.
I see that my previous focusing on intermttent short-term variations distracted me from the real problem...the excessively high long-terms. What got my attention mis-directed was the fact that the STFT1 kept going away (on both my Torque Pro and OBDLink apps....
OBDLink app is another form of OBDFusion, made by the same people). I ran the sensor tests on the Torque Pro many times, and all the sensors were check-marked. Then, about two weeks ago, STFT1 reappeared on the display.
Like I said before, both LTFT readings have been steady and the same for the two banks, initially always at 10.9, then at 11.72, and sometimes at 10.5. All these high readings are completely way above any I've ever seen while working on other vehicles. With readings like these, I should be seeing:
- 1) a large vacuum leak, which should also be hissing enough to notice, that my smoke tester should've found already,
- 2) low idle vacuum, certainly under the 24 lbs @ 710-725 rpm that I always have,
- 3) obvious fuel-rich exhaust fumes, where there are none,
- 4) though the P0313 code indicates misfires, there has been no discernable evidence that I can feel (I've always been good at noticing misfires), and
- 5) the CCV seems OK, with good vacuum (& no Mayo) at both oil filler cap and dipstick
.
However, when I checked underhood about an hour ago, I did find that there was oil blow-by on the valve cover, never before seen, and not there when I did the "check the filler cap & dipstick for vacuum" test last week. The cap was very hard to remove at that time, so I guess it's time for a new seal there.
My Foxwell showed the usual two KOMBI codes that are always present, but the two DME codes were worded differently than before
At this rate, I'm starting to believe that the X5 will
have to start showing
unmistakable signs that can't be ignored, and I can
SEE what's amiss. I'll have to use the smoke tester with stronger smoke fluid, and/or use carb cleaner on all the vacuum and intake rubber, and completely remove (again) my freshly rebuilt (with the GAS kit) DISA, and test the IAC again, as well. Otherwise, it's just parts cannon time.
Boy, do I miss those days where fuel, air, spark were easier to manage, by using simpler tools (vacuum/pressure gauge, tach/dwell meter, timing light, and a few hand tools).