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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > NA Engine (non-turbo) / Drivetrain / Exhaust Modifications > Engine noise and erratic idle



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      11-20-2011, 07:32 PM   #1
Dr Zoidberg
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Engine noise and erratic idle

2007 328i 70k miles
This is kind of embarrasing since, I take pride in troubleshooting and fixing all my own cars.. but this has be stumped. I admit I have not done too much troubleshooting yet, but since it is still under CPO , I just dropped it on the dealer... so hear it goes..

So I go for a drive on friday, and I hear my car making a minor , squealing belt noise.. Ive hear this before and figure it would just go away. Guessing I may have gotten a drop of oil on the belt when I changed my oil 4 days ago.

I continue to drive and notice the idle is not smooth and while sitting at a light the tachometer is bouncing around. ( in older cars this usually indicates a alternator failure) While the squealing noise is getting worse.

So now I think it is a belt, tensioner or a belt accessory, I inspect the engine bay.

No signs of oil on the belt,
the belts are in good condition ,
there are no shiny makrs on the belts , no rubber powder or transfer on or near any pulley, ( indicating a stuck/sticky pulley . ) and no hot spots

During troubleshooting, I find the noise goes away when I am on the gas, and then comes back when off the gas.

While coming back to my house to change cars.. the car just idles so poorly I had to keep giving it gas,, and then finally the engine just dies..

I start it right back up, and the problem disappeared... sound too.. for awhile.

My voltage is good too,, 14.4 idle and 13.7v cruising

I have replaced many a Alternator or pulley, and this sound is usually constant,

It is loudest from under front/ passenger side of the car..

My other thought is a power steering pump..

what the heck is going on , any help or conjecture would be helpful .

I am hoping its covered under CPO, but I told them to let me know what they found first
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      11-20-2011, 09:13 PM   #2
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Some possibilities-
1. Bad/clogged fuel injector
2. Bad ignition coil/spark plugs
3. Clogged throttle valves / Mass airflow sensor
4. Vacuum leak / leaky hose (e.g. PCV line)
5. Alternator dying or on the edge- still a possibility

Any codes you can read off to shed some light?
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      11-20-2011, 09:19 PM   #3
Dr Zoidberg
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Thanks for the reply,

Im not too sure its going to be related to fuel or spark, since this seems very related to the squealing and whining.. but who knows what it was..


Thats the odd part, even thought the car just died out and idled like crap , no codes were thrown ..

Unfortunatly I am waiting on a OBDII to USB adapter, so I cant check out the error logs..


I have checked out some other youtube video with a similar sound.. ie. severe belt/bearing squealing and it sounds very similar, but no one reported idle issues or car dying out .. and the intermittent nature really has me confused
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      11-21-2011, 01:53 AM   #4
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Could it be ac compressor? It is known to go bad and is powered from the belt. But the car should not die out from it. Weird. Reading the logs seems to be best course of action.
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      11-23-2011, 10:22 PM   #5
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I just heard back from the dealer,

They were able to reproduce the problem ( squealing screeching noise on idle and coming off throttle, and stumbling idle and sometimes car dying)

I thought thank god , they actually found it.. Im not imagining it

they said they got some strange ( they did not elaborate) codes off the vanos system ... and they are going to keep it over the holiday , ( hooray for loaner cars).

The combination of VANOS codes that they dont know about , and the screeching/squealing noise makes me very nervous... thank god for a warranty!

Anybody interested in wagering a guess what the heck is going on
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      11-28-2011, 07:57 PM   #6
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The dealer called, the car is done,

a brief summary , I will know more once I speak with the mechanic ,

unrelated,-
they found several codes pointing to a stuck-open thermostat- it was replaced under CPO

related-
They found several codes pointing to a valvetronic issue.
The screeching noise they said came from the valvetronic motor. ( what!! )
after troubleshooting the issue by swapping out the valvetronic motor and sensors, they found a faulty eccentric shaft sensor. and that was causing both the noise and the idle/drivability issues

A couple concerns


I dont understand how this sensor failure could cause the valvetronic motor to squeal /screech like that, but I do understand now why it was not happening under throttle.

I also dont understand that if the motor was screeching that bad , how nothing in the motor was not damaged. As I am guessing the eccentric shaft sensor was telling the motor to go beyond its limits?? no idea ?

Any help with this would be great.

Last edited by Dr Zoidberg; 11-28-2011 at 08:32 PM. Reason: I meant valvetronic , not VANOS
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      11-28-2011, 08:15 PM   #7
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Quote:
Originally Posted by Dr Zoidberg View Post
The dealer called, the car is done,

a brief summary , I will know more once I speak with the mechanic ,

unrelated,-
they found several codes pointing to a stuck-open thermostat- it was replaced under CPO

related-
They found several codes pointing to a vanos issue.
The screeching noise they said came from the vanos motor. ( what!! )
after troubleshooting the issue by swapping out the vanos motor and sensors, they found a faulty eccentric shaft sensor. and that was causing both the noise and the idle/drivability issues

A couple concerns


I dont understand how this sensor failure could cause the VANOS motor to squel/screech like that, but I do understand now why it was not happening under throttle.

I also dont understand that if the motor was screeching that bad , how nothing in the motor was not damaged. As I am guessing the eccentric shaft sensor was telling the motor to go beyond its limits?? no idea ?

Any help with this would be great.
I assume you mean done as in fixed? Not like dead? hope it worked out.
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      11-28-2011, 08:39 PM   #8
Dr Zoidberg
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I apologize for any confusion ,

My last bmw engine I built was a m20 for my scca car. So this new tech is getting me loopy ,

I was merely parroting the dealer. As the SA was incorrect,

They said it was the VANOS eccentric shaft sensor,

In actuallity it was all part of the valvetronic system


So recap from a post back

A couple concerns

I dont understand how this sensor failure could cause the valvetronic motor to squeal /screech like that, but I do understand now why it was not happening under throttle.

I also dont understand that if the motor was screeching that bad , how nothing in the motor was not damaged. As I am guessing the eccentric shaft sensor was telling the motor to go beyond its limits?? no idea ?

Any help with this would be great.
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      05-12-2012, 08:31 PM   #9
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I just bought a 2007 BMW 328i with 72k miles on it. Its under CPO. I am having a similar problem when the engine is idle and there is noise coming and the vehicle vibrating, when i press on the gas the sound goes away. Is this anyway also related to the following HVA problem related to BMW's prior to 2008 (http://www.e90post.com/forums/showpo...postcount=1057)
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      05-12-2012, 09:11 PM   #10
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2006 325xi  [0.00]
do us a favor and post at Mechanical Maintenance section
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      05-16-2012, 09:54 PM   #11
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Thought I'd jump here - my 2008 328i with 57k miles just had the eccentric shaft sensor replaced today and it's like a new car.

The car has always run rough and noisy when cold. No one was ever able to get to the bottom of it. But today it's smooth and quiet - really feels like a different car.
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      05-17-2012, 08:14 AM   #12
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pretty sure it's an expensive issue. you'll need new head. it's a problem with the head design, oil won't recirculate, etc. I may get some terms off, but i was at my mechanic's today to discuss the clunking noise (see other thread here!) and he talked just about one N52 engine in his shop that had same issues, plus warning codes thrown up and motor needed new head. it's bad, and bmw receommends this, there is a SIB on it even. I'm dreading this issue myself but mechanic said it's actually very rarely he sees this though heard of it numerous times. That was his first car, 325i E92.

In europe the cost was 3k euro to fix, so ... 4k USD give or take.

I hope it's not the same in your case of course and it's something less serious.

but my mechanic says symptoms were exactly like yours and engine doesn't basically work properly and stalls at times. New oil helps a bit, and some vanos component replacement helps temporarily but the problem is with the cover itself, it won't recirculate oil properly. There are english terms for this, but I'm translating so sorry if it's unclear, i can always go retrace the words from real oem if interested. New part is modified and fixes the problem btw.
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      05-20-2012, 01:01 AM   #13
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That's strange... my 07 328 w/ 65k KM just had it's eccentric shaft sensor replaced Friday... it was fouled/soaked with oil says the repair log. They found that while doing the n52 valve tick fix (see post 9 in this thread)
Car seems to be much, much smoother now. I'd had similar issues w/ a really low/rough idle at lights but no screeching.
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      06-03-2013, 02:54 PM   #14
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Hey Dr Zoidberg,

I am having the same exact issue with my car (2008 328i coupe).

So what is causing these problems?

Did all the problems (loud squeaky noise + at a stop, noise going away when pressing gas, and car shaking at idle) go away?
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      06-04-2013, 08:42 AM   #15
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Is this noise like a tea pot whistle?
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      07-21-2013, 02:37 PM   #16
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Johnbeck and sonic

I am having the same problem! Anyone have a solution?
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      07-23-2013, 09:57 AM   #17
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Unfortunately there is no one fits all solution to this problem. I have had this happen at least 3 different times on my car an each time the solution has been different. First time it was a bad crank sensor. Then it was a loose spark plug ground bolt to the valve cover that had worn threads and was popping out. A year after my crank sensor replacement I had to change it out again so I went and did it myself. This required removing the 3 stage manifold which has about 2,500 wires running to it which I had mixed up and forgot to attach a vacuum hose to the bottom of the manifold during reinstallation which caused the problem again. Your best bet is to scan for codes if you're having this problem with a bmw code reader, not some generic OBD2 reader. They won't tell you much of anything unless your O2 sensors are bad. After you scan the codes return here (or the mechanical maintenance section) and post your findings. If you don't scan for codes and the fault is not obvious (broken hoses etc.) then you're mostly just guessing and that gets expensive on these cars.
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