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      03-08-2013, 07:42 PM   #1
GriffBrew
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Sudden Tick / Power Loss

2006 Z4M Roadster @ ~ 62,xxx miles

Went for a drive tonight with the wife. Nice cool evening in Florida (think Spring everywhere else). Car was warmed up from a short commute home. We drove about 3-4 miles, then sitting at an intersection waiting to do a U-Turn.

I feel the steering wheel vibrate quickly once and engine sounds like the RPMs dropped almost to a stall (we're at idle already). I stare at the tach and grip the wheel to see if it happens again. RPMs visibly drop and vibration hits again. Wait...then a third time and wife can also notice it's happening. It's very brief, but it's noticeable.

I pulled into the lot across from us and it's immediately apparent there's a loud tick/knock/whatever coming from engine. I pull into the lot and pop the hood (engine still running). The sound is very apparent. I close hood and rush home as slow as possible (rushing slowly).

I drove the 2 miles home (more direct route back), never going over 2500 RPMs and trying to keep it under 2k. Clutch in as much as possible, just rolling in idle whereever possible. It's obvious the sound is there whenever a car passes us or we go by a wall/building (something for sound to bounce off).

Got home and shut it off immediately. After 5 minutes I realize I should record sound for you guys and my mechanic to hear. I pop the hood and record as I start it. Sounds 100% normal. Rev it a few times, all normal.

20 minutes later, I start it again so wife can confirm (she ran out as soon as we got home). No noise. I revved into the 5k range and I can't make the sound come back.

Thoughts? My fear is Vanos bolts, of course. But, I just had the Vanos bolts replaced 5 weeks ago. I've driven about 200 miles since then (maybe 300, definitely not much). So only way that's an issue is if they didn't do it or did it wrong. I went to a reputable shop in town, not the dealer, so I'm quite confident in their work (wouldn't have asked them to do it otherwise).

i'm pretty apprehensive to just "drive it until it happens again", but what else do I do?

Last week or so, I've noticed a 'clunk' or 'pop' going in/out of driveway. At first I feared the engine bolts, but they look ok (I have replacements, but they haven't gone in yet - I can confirm I don't have the 10.9 bolts in now). From reading, it seems this sound may be the strut towers need torqueing. Been cold here (for Florida) and I've noticed a lot more creeks in the roadster, I assume due to the cold. Probably unrelated, but just mentioning it.

While the bolts were being replaced, I had them shim the valves. There were a lot of valves way out of spec. Car sounds, and feels, much better since they did the work. Considerable valve 'ticking' went away after they did the work.

I have not replaced plugs. I don't know if/when an inspection was done on car or if the plugs were replaced at that interval. For all I know, they're original.

Only other data point is that I filled up gas yesterday. Was down to 2 miles range on the computer, so I got a very full tank. 93 octane at one of three Chevrons I frequent (this car sees a lot of the same gas). It's always possible I got 'bad gas', I suppose, though I'm not sure what that would sound like.

Any thoughts/suggestions are welcome. I don't know what else to do than try to reproduce it, but I feel that bring inherent risk of killing it.

-Ian
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      03-08-2013, 08:47 PM   #2
GriffBrew
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Also, after those initial three (or four) 'rough idle'/rpm drops, it didn't do that again at any stop lights.
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      03-08-2013, 10:38 PM   #3
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It didn't throw any codes?
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      03-09-2013, 12:24 AM   #4
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Quote:
Originally Posted by Jumbosock View Post
It didn't throw any codes?
Yeah, finally thought of that. Took me a while to get P.A. Soft going again, since I only used it once and don't really know what I'm doing.

Anyway, there isn't much I'm seeing using BMW Scan 1.4. The DME has no errors. I have a few errors for windows/radio/cellular, but those seem unimportant. Only thing that sounds like it may be interesting is from 'EKP' module - Electric Fuel Pump

EKP -> Shadow-memory:
A8/80 - Error number A8

I'm trying to track down what this means, but no luck so far. It may/may not be related. It seems that DME codes would be the place to look for misfires and/or fuel/air issues. I and I have no errors in DME, according to this.

-Ian
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      03-09-2013, 11:29 AM   #5
GriffBrew
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It's back on initial startup this morning. After recording this, I shut it off. A few minutes later, I turn it on again to try to find the source. As it's idling, the sound slow fades and is gone. I revved a bunch, trying to see if it would come back but it doesn't.

More confused now. It started when the engine was completely warmed up and continued while driving. It then wouldn't occur on restarts, once the engine had cooled slightly. Now, it happens on cold start in the morning, but fades away as it warms up.


http://youtu.be/y_lY8AdfNVs

Last edited by GriffBrew; 03-09-2013 at 11:36 AM.. Reason: I obviously don't know how to embed YouTube Videos
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      03-09-2013, 12:26 PM   #6
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It's definitely a mechanical sound.
I would shut off immediately if I heard that sound.
I would recommend towing rather than driving it like that.

Strange that it comes & goes
....sorry but not sure what it could be.
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      03-09-2013, 01:21 PM   #7
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I agree it sounds bad. One possibility why the noise goes away is bad or gummed up timing chain tensioner. I'm pretty sure the M engine uses oil pressure for this function. If the chain stays loose and jumps a tooth it can do some expensive damage.
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      03-15-2013, 04:35 PM   #8
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Left it with the mechanic this week. He heard it only slightly on cold starts. He thinks the sound is emanating from behind the crank balancer, but not exactly sure where or what it is. When I went in to get it today, it wasn't making this noise on cold start. It started to make it pretty faint after a while, but it's hard to say its the same noise, since the volume is now lower.

I'll be watching this closely for a while, I guess. It's pretty odd and very frustrating its so inconsistent.
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      07-07-2013, 12:14 PM   #9
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Op, any update on this? I've experienced the exact same, as soon as I hear it, turned off the engine and at restart noise all gone. My initial thought was vans bolts but you replaced them so.. One other thing is maybe rod bearing?..
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      07-07-2013, 12:15 PM   #10
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As Pete c said it sounds very much like chain related mechanical
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      07-07-2013, 12:21 PM   #11
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Since you recently replaced the VANOS bolts, I assume that you removed the spark plugs. On reinstall, were they torqued correctly? May worth checking, it costs just a bit of time.
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      07-07-2013, 02:05 PM   #12
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Quote:
Originally Posted by RobertRO View Post
Since you recently replaced the VANOS bolts, I assume that you removed the spark plugs. On reinstall, were they torqued correctly? May worth checking, it costs just a bit of time.
That's a good one. Also,

Header bolts and sticky valve, which can come and go.
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      07-09-2013, 09:35 PM   #13
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Bottom line is: this hasn't come back. One other time I felt the strange idle drop while sitting at a light. I've seen other reports of this on the S54, often occurring more frequently than mine. I'm enjoying the car but paying attention for signs of an issue. I'm seeing none at this point.

I changed plugs AFTER this occurred, coincidentally. I don't know why, but I didn't have them do plugs when adjusting valves. I definitely torqued them correctly, can't say what the shop did before (though I trust them).

As for timing chain, I would like to think they'd have mentioned an issue if they noticed one while in there. Correct me if I'm wrong, but the timing chain is mostly (fully?) exposed during the vanos blot replacement procedure. They did change engine belts at the same time so maybe the noise was a belt wearing funny and settling.

Of course, I barely drive it at all now that its summertime (fall/winter is convertible season here), but it's yet to occur even during a hot day and spirited drive for an hour (there was no correlation to heat or driving pattern before, I'm just stating the few drive cycles it's seen).

My Blackstone report was good last fall during oil change. I might pull a sample soon just to verify things are ok on the inside. Though, this wouldn't tell me that the timing chain is loose and about to slip a tooth and destroy the engine. But I tend to not imagine such things or I can't enjoy my car.

One other item is that the vent hose was not pushed all the way down on the intake side (right side) while at the mechanic. He noticed and pushed it back in until it clicked. I'm honestly not clear what this does so no idea if it could've caused the noise, but I doubt it. Part 2, here http://www.realoem.com/bmw/showparts...97&hg=11&fg=15
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      07-09-2013, 09:52 PM   #14
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Since two people have PMed me about this, I want to stress that I'm not concerned and my mechanic's not concerned. Maybe we're wrong, but it's not reproduceabe and the car behaves normally. No codes, no funny noises and no issues driving.

One item he and I discussed is that it did NOT get louder when revving and did not seem to cause vibration, shaking or other noticeable changes in the car. Those could be signs of a bent rod, he tells me, but it's just not happening.

My original title about power loss should be considered a separate event. This may/may not be related to the very specific mechanical sound at idle that I recorded above. No correlation has been confirmed. It did not reoccur on cold starts, as the noise did. This is referring to the idling engine dropping its rpms while stopped. If you search this you'll turn up some others discussing it on an S54. My engine is pulling hard and drives fine. I have no power loss while driving.

The best thing for anybody to do is what inTgr8r said: take it to a shop who knows what they're doing. Not the dealership, a shop who knows S54s. These engines make a lot of noises. All the posts about vanos noises and engine concerns have people scared about these engines. I've thought about deleting mine because of it, but I'm leaving it as a record of an overly protective car owner. Or, if the car dies, a lesson in being more careful :-p
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      07-09-2013, 10:57 PM   #15
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Could it be a *SERIOUSLY* stuck valve? At any rate I bet the idle drop happened because #2 wasnt sealed, providing a vacuum leak. Then dipping under idle caused something to go amiss, causing this terrible noise...

Let us know if anything happens with it, otherwise enjoy it... as long as the problem is gone and there are no other symptoms, I dont see how there could be an issue with driving the car
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      07-10-2013, 09:48 AM   #16
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Quote:
Originally Posted by Z4inAZ View Post
Could it be a *SERIOUSLY* stuck valve? At any rate I bet the idle drop happened because #2 wasnt sealed, providing a vacuum leak. Then dipping under idle caused something to go amiss, causing this terrible noise...

Let us know if anything happens with it, otherwise enjoy it... as long as the problem is gone and there are no other symptoms, I dont see how there could be an issue with driving the car
S54 engines have solid lifters not hydraulic ones. A stuck valve would not go away.... There would be other issues to resolve then.
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      08-12-2013, 06:45 PM   #17
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Sounds just like mine but the noise has NEVER gone away. I'm now deciding what rod bearings and bolts to use... good luck.
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      08-12-2013, 06:55 PM   #18
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Quote:
Originally Posted by 08E86M-475 View Post
Sounds just like mine but the noise has NEVER gone away. I'm now deciding what rod bearings and bolts to use... good luck.
How long (mileage) have you had a unique noise? Interested why you're assuming rod bearings - have you done oil analysis or anything that points to bearings?
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      10-20-2013, 08:17 PM   #19
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I have similar noise coming from mine... 2006 with 55xxx. I feel mine only at idle and it is more prevalent after warming up. But the EXACT sound. No loss of power... I took it to an indie shop and they suggested a vanos swap but they could not guarantee that would fix it. any updates or progress??
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      10-20-2013, 11:49 PM   #20
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Quote:
Originally Posted by a13xkim View Post
I have similar noise coming from mine... 2006 with 55xxx. I feel mine only at idle and it is more prevalent after warming up. But the EXACT sound. No loss of power... I took it to an indie shop and they suggested a vanos swap but they could not guarantee that would fix it. any updates or progress??
Have you replaced the vanos-to-camshaft bolts?
Mine sheared off 3 bolts by 40k miles.
Ticking was from the remaining 3 loose bolts and the sheared-off heads flopping around.
Vanos was fine.
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      03-12-2014, 05:48 PM   #21
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Yup mine was the same issue. Had the entire vanos done since it was off. Ptia
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      03-13-2014, 02:41 PM   #22
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Had same issue, except car would die as well. 3 bolts sheared. Replaced entire VANOS system with Beisan Systems parts.
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