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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Thu, Nov-07-2019, 11:53:51 PM   #1
evanr614
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Default Random Engine Knock When Sitting Still

Iím experiencing a random engine knock that can be felt throughout the vehicle. I would not consider it violent at all, itís pretty mild but still a knock. So far there is no correlation as to when it occurs whatsoever but I have no idea where it is coming from. The idle does not fluctuate with the knock. Sometimes it is 1 knock or a series of 2 or 3 ďfluttersĒ back to back. Where is the best place to start to diagnose this? All injectors were sent off to be flow tested and cleaned, fuel filter has been changed recently, changed spark plugs a couple of weeks ago, always use 93 gas, no codes being thrown. The car has not had a valve adjustment for a long time to my knowledge, not sure if that would matter. Anything helps!! Thanks
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Old Thu, Nov-07-2019, 11:55:32 PM   #2
mrgizmo04
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Default Re: Random Engine Knock When Sitting Still

Most likely a loose heat shield, but can you get a misfire counter to see if that is active?

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'85 528e 164k miles (sold)
'05 M3 6MT coupe

All DIY: VANOS, WPC rod bearings, full SS (SS stepped V1 headers, catted S1, stock S2, SS sport), AFD E85 Proflex kit, Ohlins R&T/Hyperco 375f Swift 672r/GC street tops and camber plates, ST40 355 pfc08, 330 ZHP steering rack, diffsonline 4.1 diff with rem polish, E60 short shifter lever, AKG black diff bushings/subframe bushings, Rogue rtab, Sachs clutch/flywheel, rear main, Beyer driveshaft, valve adjustment, cooling refresh.

Happy to help with VANOS or any other DIY job around NorCal. Have various specialty tools (VANOS, RTAB, engine bar, valve adjustment, tranny jack, ball joint separator, pilot bearing puller, tap&die kit, etc).
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Old Thu, Nov-07-2019, 11:56:51 PM   #3
evanr614
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Default Re: Random Engine Knock When Sitting Still

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Originally Posted by mrgizmo04 View Post
Most likely a loose heat shield, but can you get a misfire counter to see if that is active?

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Definitely not a heat shield. It is more of a thud. Can that be done with an OBD tool and an iPhone?


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Old Fri, Nov-08-2019, 12:08:19 AM   #4
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Default Re: Random Engine Knock When Sitting Still

Slowly rev the rpm up and see if the knock rate follows, then it is engine components related.
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Old Fri, Nov-08-2019, 12:09:54 AM   #5
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Default Re: Random Engine Knock When Sitting Still

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Originally Posted by sapote View Post
Slowly rev the rpm up and see if the knock rate follows, then it is engine components related.


Iíve never seen it correlate with using the throttle. Always when at a stand still. Car runs fantastic otherwise


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Old Fri, Nov-08-2019, 12:52:06 AM   #6
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Default Re: Random Engine Knock When Sitting Still

Heater valve?


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Old Fri, Nov-08-2019, 02:18:31 AM   #7
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Default Re: Random Engine Knock When Sitting Still

I think knock is the wrong word here. Its probably missing once in a while, how old are your coils?
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Old Fri, Nov-08-2019, 02:22:54 AM   #8
evanr614
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Default Random Engine Knock When Sitting Still

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Originally Posted by fattycharged View Post
Heater valve?


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what makes you say that?

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Originally Posted by icecream View Post
I think knock is the wrong word here. Its probably missing once in a while, how old are your coils?

they are probably all original. can they miss without throwing codes? i would hate to replace all the coils for no reason


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Old Fri, Nov-08-2019, 03:01:43 AM   #9
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Default Re: Random Engine Knock When Sitting Still

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Originally Posted by evanr614 View Post
what makes you say that?




they are probably all original. can they miss without throwing codes? i would hate to replace all the coils for no reason


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Before mine go out they seem to do what you describe. Its always just one at a time but smarter to replace all. At least you should have a spare in the glove box to save yourself some headache.
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Old Fri, Nov-08-2019, 03:54:03 AM   #10
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Default Re: Random Engine Knock When Sitting Still

I have the same problem occuring from time to time.

Knock is probably the word I would choose to describe it too. It would knock and you can feel the engine just skip a beat pretty much. Goes away with any throttle input.

I've changed pump, filter, fuel regulator, injectors, coils & sparks. Kinda gave up chasing it. Doesn't do it all the time either. I catch it from time to time.
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Discussing Random Engine Knock When Sitting Still in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)