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09-27-2011, 09:34 AM | #46 | |
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09-27-2011, 09:39 AM | #47 | |
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By the way, detonation (not pre-detonation) and pre-ignition are two completely different damage mechanisms. What is being experienced at low load is likely detonation, or the spontaneous combustion of the mixture ahead of the flame front. Pre-ignition is the combustion of the mixture before the spark plug fires by a hot object in the cylinder. It is far more damaging than detonation. |
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09-27-2011, 10:18 AM | #48 |
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I think the knocking you might be hearing is coming from the drivetrain, Clutch and flywheel. Engine on the otherhand is not knocking or lugging. Lugging really wont damage anything, I was talking more about knockin. We dont know if his motor really os knocking or not. OP if you want the internet to diag this for you take a vod and post it too, other wise we are all guessing. |
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09-27-2011, 10:38 AM | #49 |
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thanks for the video. in my case the knocking doesn't happen the first moment I kick down, it happens around 1800-1900 rpm. it doesn't make any noise, it feels like an engine hiccup, the passengers can feel it too when they pay attention. I also get a few random knock/bump when I am siting warming up the car in the morning. Does anyone get that?
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09-27-2011, 10:57 AM | #51 |
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Sounds like you have an intermittent miss. Have the car looked at. Possible from what you said on previous post, your plug seals are slightlly leaking oil. Spark plug tubes full of oil will cause an intermittent miss.
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09-27-2011, 10:59 AM | #52 |
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09-27-2011, 12:11 PM | #53 |
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09-27-2011, 12:22 PM | #54 |
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For all those that think driving at 1500rpm is really bad and/or will hurt your engine, I've noticed in D3 (DCT), it's will shift into 7 at a steady speed ~50mph/no accel, which I've noticed is around 1500rpm (or certainly less than 2k, IIRC). If driving at that RPM was that bad, I don't think M would have allowed the DCT to be programmed that way (unless low RPM in higher gears is better than low RPM in low gears). This is actually one reason I don't like the D modes that much. D3 is too granny, D4 is a bit too aggressive for everyday driving.
To the OP, I've definitely noticed low torque at those RPMs, but never any stumbling. Sound like an issue. Has this been happening for a while? Sure you don't just have a bad tank of gas?
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09-27-2011, 12:46 PM | #55 | |
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I know it has a lack of torque but its not bad either Some say coasting at 2,500 RPM saves more gas because it has less stress on the engine but I don't know
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09-27-2011, 12:48 PM | #56 |
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09-27-2011, 01:24 PM | #57 |
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I first noticed the condition a few months ago. Spark plugs looked really bad, nothing else were found. The new plugs seem to have fixed the problem, but it is coming back after only 2-3 months.
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09-27-2011, 02:07 PM | #60 |
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Re idle when cold: My M3 rumbles and sounds rough at start, for about the first 15 seconds or so. This concerned me, so I checked three other brand-new M3s, and they all did the same thing.
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09-27-2011, 02:24 PM | #61 |
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Love that sound! Wish it would stay that way. Hate it when the cats warm up.
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09-30-2011, 01:20 AM | #62 |
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update: it wasn't that easy to gain access to all the spark plugs, so we pull one out and it looked new. since spk plugs were changed only few months ago, and the fuel filter were never changed(08 car), we decided to try a new fuel filter first.
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09-30-2011, 06:41 AM | #64 | |
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if you're cruising, there's no reason to be anywhere near that high. i cruise around 2k, and downshift when needed.
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09-30-2011, 10:08 AM | #65 |
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Its also a recipe for making your car more fun. Those rpms are still low. Shifting before 5000 is still pretty conservative. And cruising between 3 and 5 is called being on the freeway, its required. Try 8600 and don't go below 5000.
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09-30-2011, 10:15 AM | #66 |
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cruising on the freeway usually has me at about 2850-2900...
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