Diagnosing squeal and misfires

Grainwashed · 04-02-2022, 07:30 PM

I have a 2011 135i, currently at 65k miles. A couple months into owning the car, it developed an odd squeal at idle once it reached operating temp and the rpms would dip, the car would idle kinda rough until the rpms bounced back up. Both issues happened at the same time. I really didnt think much of it and just wrote it off as an annoying thing I would deal with someday.

Fast forward a few months to now, and the squeal has gotten a bit worse but the misfires are much worse and present under more conditions. Basically any time it revs up and falls down to idle rpms (under load or not), the squeal happens and the car starts misfiring. I tried everything I could think of that might be the issue, new belt and tensioner, new idlers, new ac compressor. Then somebody on another forum set me on at least the right path to fixing it. He told me that our cars have a common failure point in the pcv system that can cause everything that im talking about. I groaned at the cost of a new valve cover, but I just wanted my car back. I had cracked my oil fill cap open while it was making the issues and the car started running much better briefly and the squeal went away.

After installing the new valve cover yesterday and thinking I had finally fixed it... nope. Everything still happens the exact same. Does anybody have any guidance for me? I'm leaning towards one or both of the crank seals being bad but I genuinely dont know how it would cause misfires, and I'm leaking zero oil. I'm bringing it to a shop this week but I would like to come to them with an idea of exactly whats wrong with it so I don't spend more than I have to for them to diagnose the issue before fixing it.

I'm sorry if this is the wrong area to post this, I made this account ten minutes ago so I'm not super familiar with the forum contents. If I'm in the wrong area could a mod kindly move me to the right area?

The noise sounds exactly like whats heard in this video, but it's somewhat constant at idle as well as after the rpms drop

Aceway · 04-02-2022, 07:54 PM

When my eccentric sensor took a crap the engine made a really bad shrieking noise and would misfire. That could be possible but it's hard to tell unless you can pull up the error codes from your car. Perhaps take a video of the noise and post it?

Grainwashed · 04-02-2022, 07:56 PM

Quote:

Originally Posted by Aceway

When my eccentric sensor took a crap the engine made a really bad shrieking noise and would misfire. That could be possible but it's hard to tell unless you can pull up the error codes from your car. Perhaps take a video of the noise and post it?

It's not a really bad shriek, its more like a short squeal or chirp. It sounds exactly like the noise that's in so many of the "bad pcv valve" threads I've seen on here, let me see if I can find a video of it

Grainwashed · 04-05-2022, 04:31 PM

I FIGURED IT OUT. I unplugged my jb4 and the car runs like a top now, no squeal or misfires. I've heard before that some of our cars dont like the jb4 tunes and the timing gets thrown off and the car runs bad, I just didn't think that was the issue. MHD flasher is already in the mail so I'm glad I had the forethought to order one in advance of the car getting fixed and tuned

WilsoN55 · 04-06-2022, 12:50 AM

A tip: check the quality of your main engine ground cable and your starter wire at the firewall.. both are prone to fail and will send you down a rabbit hole as electronics will start to malfunction without the proper voltage. They are cheap and easy to replace. If the ground cable doesn't look new, replace it.

I realize you seem to have solved your issues, but you won't regret it.

04-02-2022, 07:30 PM	#1
Grainwashed Enlisted Member 5 Rep 44 Posts Drives: 2011 BMW 135i Join Date: Apr 2022 Location: Washington iTrader: (0)	Diagnosing squeal and misfires I have a 2011 135i, currently at 65k miles. A couple months into owning the car, it developed an odd squeal at idle once it reached operating temp and the rpms would dip, the car would idle kinda rough until the rpms bounced back up. Both issues happened at the same time. I really didnt think much of it and just wrote it off as an annoying thing I would deal with someday. Fast forward a few months to now, and the squeal has gotten a bit worse but the misfires are much worse and present under more conditions. Basically any time it revs up and falls down to idle rpms (under load or not), the squeal happens and the car starts misfiring. I tried everything I could think of that might be the issue, new belt and tensioner, new idlers, new ac compressor. Then somebody on another forum set me on at least the right path to fixing it. He told me that our cars have a common failure point in the pcv system that can cause everything that im talking about. I groaned at the cost of a new valve cover, but I just wanted my car back. I had cracked my oil fill cap open while it was making the issues and the car started running much better briefly and the squeal went away. After installing the new valve cover yesterday and thinking I had finally fixed it... nope. Everything still happens the exact same. Does anybody have any guidance for me? I'm leaning towards one or both of the crank seals being bad but I genuinely dont know how it would cause misfires, and I'm leaking zero oil. I'm bringing it to a shop this week but I would like to come to them with an idea of exactly whats wrong with it so I don't spend more than I have to for them to diagnose the issue before fixing it. I'm sorry if this is the wrong area to post this, I made this account ten minutes ago so I'm not super familiar with the forum contents. If I'm in the wrong area could a mod kindly move me to the right area? The noise sounds exactly like whats heard in this video, but it's somewhat constant at idle as well as after the rpms drop Last edited by Grainwashed; 04-02-2022 at 08:01 PM.. Reason: Added video for clarity
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04-02-2022, 07:54 PM	#2
Aceway Captain 455 Rep 875 Posts Drives: E82 135i / F25 28i Join Date: Feb 2018 Location: SoCal iTrader: (2)	When my eccentric sensor took a crap the engine made a really bad shrieking noise and would misfire. That could be possible but it's hard to tell unless you can pull up the error codes from your car. Perhaps take a video of the noise and post it?
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04-05-2022, 04:31 PM	#4
Grainwashed Enlisted Member 5 Rep 44 Posts Drives: 2011 BMW 135i Join Date: Apr 2022 Location: Washington iTrader: (0)	I FIGURED IT OUT. I unplugged my jb4 and the car runs like a top now, no squeal or misfires. I've heard before that some of our cars dont like the jb4 tunes and the timing gets thrown off and the car runs bad, I just didn't think that was the issue. MHD flasher is already in the mail so I'm glad I had the forethought to order one in advance of the car getting fixed and tuned
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04-06-2022, 12:50 AM	#5
WilsoN55 N55 E82 DCT /// N57 F10 Daily <-- 93 Rep 123 Posts Drives: N55 E82 DCT /// N57 F10 Join Date: Aug 2021 Location: Ontario iTrader: (0) Garage List 2011 BMW 135i [0.00] 2015 BMW 535Dx [0.00]	A tip: check the quality of your main engine ground cable and your starter wire at the firewall.. both are prone to fail and will send you down a rabbit hole as electronics will start to malfunction without the proper voltage. They are cheap and easy to replace. If the ground cable doesn't look new, replace it. I realize you seem to have solved your issues, but you won't regret it.
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