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Old 02-13-2013, 01:20 PM   #1
Jakall
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Mystery tapping refuses to be diagnosed

After over a year worth of thousands of dollars of near-monthly diagnostics, I turn to the online BMW community to help me solve a tapping which has thus far been a complete mystery to all the euro-specialized mechanics who have looked into it. The tapping happens under very specific circumstances, and I have a LOT of diagnostic/repair intel regarding known-good components, so I'm very confident you guys might be able to save the day!

The car is a 2003 325Ci, so it has an M54 engine, with a Steptronic transmission. In December 2011 I had the engine rebuilt with new pistons and a good-quality used block from Turner Motorsports... the prior engine's cylinders were heavily worn, so it was burning through oil like crazy (2qt/month). Oil use aside, the car performed well and at low speed the engine was whisper-quiet, as a BMW engine should be.

After the rebuild, the engine sounds like a diesel while idling. When accelerating, a tapping (about 5 taps/second) starts abruptly at ~1,500rpm (think parking lot speeds), remains steady if I hold the throttle position, and taps faster as I give it more gas. The tapping is eventually drowned out at higher speeds/RPMs. As soon as I take my foot off the pedal, it lets off a couple more taps for about a half second then stops. The tapping is clearly audible when the engine is cold and the windows are open. Giving it gas then letting off the pedal consistently produces and stops the tapping. It gets quieter when the engine warms up (15min of driving or so). Shortly after the rebuild, the tapping would be almost entirely absent after the engine warmed up, but after a year of tapping, it has recently been getting louder (especially in winter) and is still audible even after the engine is warmed up. The engine sounds like a diesel regardless of operating temperature. I can now hear the tap even when the engine is at idle or warm, though again, it kicks in far louder as soon as the RPM / engine load reaches a certain point.

Stethoscope diagnostic hasn't been helpful, and simply indicated that the sound seems to be coming from the block somewhere... it sounded loudest when probing the low end. Initial thoughts were the DISA, VANOS, chains, lifters, and main bearings, but as you'll see below, all have been replaced or checked to no avail.

Here's a relatively comprehensive history of what has been replaced or checked:

June, 2011
New starter
New valve cover

???, 2011
New fuel pump

Dec, 2011
Used engine block w/ new pistons from Turner Motorsport
Head set
Main bearing set
Rod bearing set
New DISA variable intake unit

(tapping starts)

???, 2012
VANOS rebuilt with Beisan Systems o-rings (seals repair kit) and bearings (rattle repair kit)
New PCV valve

Oct 2012
New alternator

Nov 2012
Oil pan pulled, bottom-end inspected
New main bearing set
New front-right shock
New spark plugs

Dec 2012
Head pulled and inspected, new head gasket
Checked the PCV system to make sure it operated correctly
Replaced rod bearings
Inspected timing chain and guide rails, light wear found on drivers side rail
Replaced all lifters
Inspected VANOS system and cam chain tensioner and rails
Inspected exhaust system for leak
Inspected DISA unit
Inspected air intake boots
Visually inspected vacuum hoses and intake manifold

Some mechanics thought it was a wrist-pin issue, but sequentially disabling the cylinders didn't stop the tapping, and I'm told the engine runs way too smoothly (tapping aside) to have a bad cylinder. The next best guess was a chain issue, but I trust the mechanic who inspected the chains and he said it all looked just fine. At this point, as far as I'm aware, the only things left to do are take it to the dealer (though I doubt they'll be able to tell me anything the +5 veteran mechanics who listened to it couldn't) or completely tear the block apart and go through it all piece by piece. Given that I've replaced most of the engine at this point, the good new is that once I get this tapping fixed, the engine will be pretty much good as new.

Anyone have any ideas as to what might be the cause of the tapping? I'd greatly appreciate any solid diagnostic proposals as well!
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Old 02-13-2013, 01:22 PM   #2
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Would help if you posted a video of the noise
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Old 02-13-2013, 01:25 PM   #3
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It's impossible to determine if the sound is from the top end or bottom end? Could be rod bearings, piston slap, a sticky lifter? Could even be a faulty DISA, since it started after you replaced it. Hopefully you kept the old one...
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Old 02-13-2013, 01:34 PM   #4
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Quote:
Originally Posted by E46Mango View Post
Would help if you posted a video of the noise
Thanks for the reply... I'll post a video later today.

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Originally Posted by lcoleman View Post
It's impossible to determine if the sound is from the top end or bottom end?
The at-idle tap seemed louder from the bottom end, but was impossible to isolate... I was there and listened to it myself when my mechanics probed it. The far louder at-load tap would be easier to hear and thus might be easier to isolate, but I'd have to stethoscope it on a dyno to make that happen.

Quote:
Could be rod bearings, piston slap, a sticky lifter? Could even be a faulty DISA, since it started after you replaced it. Hopefully you kept the old one...
Rod bearings were replaced; no change. Pistons were disabled one-by-one (though I don't recall whether they cut power to the injectors or the coils); no change. Lifters were all replaced; no change. Unplugging the DISA was the first thing I tried; no change.
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Old 02-13-2013, 02:34 PM   #5
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Is it possible you got a bad lifter? It's not unheard of.
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Old 02-13-2013, 02:53 PM   #6
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Originally Posted by Jakall View Post
Thanks for the reply... I'll post a video later today.


The at-idle tap seemed louder from the bottom end, but was impossible to isolate... I was there and listened to it myself when my mechanics probed it. The far louder at-load tap would be easier to hear and thus might be easier to isolate, but I'd have to stethoscope it on a dyno to make that happen.


Rod bearings were replaced; no change. Pistons were disabled one-by-one (though I don't recall whether they cut power to the injectors or the coils); no change. Lifters were all replaced; no change. Unplugging the DISA was the first thing I tried; no change.
I don't know if doing a power balance test (unplugging the coils) would necessarily rule out damaged wrist pin since there's still forces exerted on the moving parts. just a thought
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Old 02-13-2013, 03:05 PM   #7
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I thought the same about bearings. The first post says main bearings, the next says big end bearings...two different things. I imagine the sound would still change, though.

Getting quieter as it warms up makes me suspect something in the head.
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Old 02-13-2013, 03:10 PM   #8
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I would guess it's a lifter or injector making the tapping noise.
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Old 02-13-2013, 03:22 PM   #9
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I would guess it's a lifter or injector making the tapping noise.
I have a tapping injector myself - it is rather easy to pinpoint the location of the tapping if that is the OP's problem.

I suspect not though based on what I've read about the source of the tapping being somewhat non-locatable?
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Old 02-13-2013, 03:32 PM   #10
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The dealer will have a lot more foot notes and raw experience with BMW's overall and will have a lot more info than any indy mechanics. In the worst case they might have someone from BMW NA come check it out.
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Old 02-13-2013, 03:43 PM   #11
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Looks like a pretty good list of things have been touched.
Without knowing how loud the sound is, but solely based on frequency, I'd test EVAP purge valve by unplugging it.
If it's positively coming from the bottom end after all of that work, I'd look at the oil pump.

In for the video.
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Old 02-13-2013, 06:28 PM   #12
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Originally Posted by lcoleman View Post
I thought the same about bearings. The first post says main bearings, the next says big end bearings...two different things. I imagine the sound would still change, though.

Getting quieter as it warms up makes me suspect something in the head.
That's what made me think it might be a bad lifter that takes a really long time to get pressurized.
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Old 02-13-2013, 06:56 PM   #13
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Just throwing this out since it was a replacement block and the knock sensors were either replaced or disconnected / reconnected for the install..... have you checked the real time voltage readings from the two knock sensors?
I see about 0.02 -0.06 volts on my knock sensors at warm idle. Before starting the voltages are 0.0 on both, on a cold start I see up to about 0.10 volts.

I also see a "Knock Control Adaptation" with a range of 0.0 to 1.0 with AutoEnginuity Software. It shows about 0.1 for the first 10 minutes after a cold start and then drops to 0.0.
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Last edited by shanneba; 02-13-2013 at 07:09 PM.
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Old 02-14-2013, 07:37 AM   #14
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My shop is the one trying to help Jason with his car. We are Krauthouse Motorsports. I am Sparta.... wait wrong post. We replaced all of the lifters with good quality lifters from one of my suppliers. No Chineese crap. The valve train looks good. We did a very thorough visual inspection when we were replacing the lifters to look for anything that might be wrong. I know visual inspections wont catch everything though.

We checked the DISA and took it out and inspected it. There was some gritty particles in the intake when we took it out.

After we replaced the rod bearings we actually got a code in INPA for engine too quiet. Which we thought was a good sign. We reset all of the adaptations and drove it around some and the code didn't come back.

We ran a scope on each injector to listen for noise on them. They all sound the same like any Bosch injector does.

I did notice some noise on the exhaust side of the vanos unit and we debated rebuilding it but Jason said that it was rebuilt by the previous shop. We know the previous shop and they do good work.

We serviced his transmission when we replaced the rod bearings. There aren't any weird sounds or anything coming from it.

Thats about all i've got for now. Thanks for all of your help. I just bought an e46 for my wife and will probably hang out on here some more.
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Old 02-14-2013, 09:31 AM   #15
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After we replaced the rod bearings we actually got a code in INPA for engine too quiet. Which we thought was a good sign. We reset all of the adaptations and drove it around some and the code didn't come back.
The engine too quiet codes makes me think even more about a thorough check of the knock sensors and electrical connection is in order.

Hopefully the car has at least 91 octane fuel, the default maps in the ECU are set for that octane.
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Old 02-14-2013, 10:20 AM   #16
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This morning I got some great recordings of the tapping both at idle and while driving. I'll upload and post links later today.

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Originally Posted by 330iPilot View Post
Is it possible you got a bad lifter? It's not unheard of.
After having replaced the lifters and hearing no change in sound, I doubt it's the lifters.

Quote:
Originally Posted by Vin Vega View Post
The dealer will have a lot more foot notes and raw experience with BMW's overall and will have a lot more info than any indy mechanics. In the worst case they might have someone from BMW NA come check it out.
I'm willing to take it to the dealer if there's a reasonable chance they can identify the issue. My concern is that they'll want to tear the entire engine apart (all while I pay dealer labor rates) only to end up not even fixing the problem. Add in the unpredictability of when they'll finish the job (I can see "have someone from BMW NA come check it out" turning into "sorry, but we'll need your car for a month") and it gets to be a pretty last-ditch proposition.

I absolutely love my E46 and will never part with it, but at that point it would be more practical for me to buy a new car and stick the E46 in the garage. I can't afford to blank-check a repair bill at the moment.

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Hopefully the car has at least 91 octane fuel, the default maps in the ECU are set for that octane.
I run with 89, but will try 91 to see if there's any difference.

Fantastic replies so far, guys. Thanks for the support!

Last edited by Jakall; 02-14-2013 at 10:21 AM.
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Old 02-14-2013, 10:31 AM   #17
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You should be able to find 93 octane here in Indiana. I see there are several CountryMark gas stations in your area,Bedford and Loogootee, they sell Top Tier gasoline (BMW suggested) and use crude oil only from the USA!!
http://www.countrymark.com/retail/
Wish you were closer to Indy, I would check the sensors for you with my software.
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Old 02-14-2013, 10:41 AM   #18
Jakall
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I actually live in Bloomington, and find myself in Indy frequently. That's a very generous offer, and I might just take you up on that.
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Old 02-14-2013, 10:47 AM   #19
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A video would really help. Other than the tapping noise, how does the car run?
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Old 02-14-2013, 11:38 AM   #20
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My thought was that if you had a bad lifter, and then replaced it with a bad lifter, you would still get the noise. But it sounds like your mechanic put in some good ones so I'm with you on ruling it out.
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