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Discussion Starter · #1 ·
I've got an issue with my bimmer where it likes to run rough around 2500+ RPMs. It will run rough and performance sucks when it does, making it difficult to get up to speed in any gear without shifting very early.

I've asked mechanics and they've told me to check the O2 Sensor, check for vacuum leaks, and test to see if any coils are going out. O2 Sensor is new, I haven't found any vacuum leaks, and all coils test good.

When I asked them if it could be the VANOS system, none of them knew what I was talking about. I did my research on it, find out it's another VVT system, and I'm assuming that it's bad.

I've found rebuilt ones from Dr. Vanos for $375 ($275+$100 core).

My question is, could this be my issue? Plugs are new, coils are good, O2 is new, no vacuum leaks found, and the issue is intermittent. It used to happen once every two weeks or so for two days, now it is constant.

When searching, I've found people with similar issues but at lower RPMs (800-1500) with the comments suggesting this was the issue.

I appreciate any help you guys can offer!
 

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Discussion Starter · #9 ·
All of it ?
Skip to 0:25


Best I can get while also driving. I'll try better tomorrow on my way to work (flat, wide open road) with the window down so you can better hear the noise.

It's an extreme power loss right around 3k depending on the gear (5th gear is exactly 3k, whereas 1st is like 2700).

What's odd is right before I took this video, I went to the store (about 1/4 mile from my house) and had no issues then.
 

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It does not sound like a VANOS issue to me. Normally when the VANOS fails you loss power below about 3k. The car can fell like you have a turbo because around 3k it will suddenly gain a bunch of power. This is the exact opposite of what you are describing. First thing I would suggest you do is smoke test the car to make sure there are no vacuum leaks. I know you already checked for them, but vacuum leaks can be very hard to chase down. You can do the smoke test you self for the cost of a cigar.
https://youtu.be/zMok2y05jNE

Next have you coils professionally checked. With out a coupe grand in equipment some issues with coils can be impossible to detect. A coil can show fine on a multimeter and produce a spark and still not be working right. Also what spark plugs are you using? The premium 4 prong platinum plugs have be know to case all sorts of issues in M50s. The cheaper copper 1 prong spark plugs are the best for a M50. If you are not running them I would suggest you change your spark plugs again.

Once you are done with that, report back and we will go from there.
 

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Discussion Starter · #11 ·
It does not sound like a VANOS issue to me. Normally when the VANOS fails you loss power below about 3k. The car can fell like you have a turbo because around 3k it will suddenly gain a bunch of power. This is the exact opposite of what you are describing. First thing I would suggest you do is smoke test the car to make sure there are no vacuum leaks. I know you already checked for them, but vacuum leaks can be very hard to chase down. You can do the smoke test you self for the cost of a cigar.
https://youtu.be/zMok2y05jNE

Next have you coils professionally checked. With out a coupe grand in equipment some issues with coils can be impossible to detect. A coil can show fine on a multimeter and produce a spark and still not be working right. Also what spark plugs are you using? The premium 4 prong platinum plugs have be know to case all sorts of issues in M50s. The cheaper copper 1 prong spark plugs are the best for a M50. If you are not running them I would suggest you change your spark plugs again.

Once you are done with that, report back and we will go from there.
I really appreciate the info. I'll try a smoke test when I get a chance and I'll probably end up replacing all the coils. The PO said he had the same issue and replaced two coils with ones out of a junkyard.

The plugs in it are the NGK BKR6EK (2288) Dual-tip. All my research showed these were the best plugs to use in the M50TU engines.

As far as the coil test, I'll shop around and see how much a shop will charge to have them tested. Labor rates are insane here ($80/hr is the average) so I try to do everything myself.
 

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D'oh, You Kids!
1984 633CSi, 1985 635CSi, 1985 325e, 1987 325is, 1993 325is, 1995 318is, 1995 M3, 2003 F150
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FYI $80/hr shop rate is CHEAP.

The NGK BKR6EK plugs are the right ones. :thumbup:
 

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Discussion Starter · #13 ·
FYI $80/hr shop rate is CHEAP.

The NGK BKR6EK plugs are the right ones. :thumbup:
I know it's not that bad compared to some states but in my area it's ludicrous. Tri-county area is farm country with not a lot going on. Cheapest labor rate I've found is $65/hr but I'll still shop around before shelling that out lol.
 

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hookersandblow
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I know it's not that bad compared to some states but in my area it's ludicrous. Tri-county area is farm country with not a lot going on. Cheapest labor rate I've found is $65/hr but I'll still shop around before shelling that out lol.
$100/hr for all the BMW specialists here in Cincinnati.
 

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Right around 3k rpm is where the vanos solenoid should activate and allow oil flow to adjust the intake cam timing. Try disconnecting the electrical connection from the solenoid and see if there's any difference in how the engine runs. If the vanos solenoid is bad, rebuilding the vanos assy won't fix anything.
 

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Discussion Starter · #17 · (Edited)
Right around 3k rpm is where the vanos solenoid should activate and allow oil flow to adjust the intake cam timing. Try disconnecting the electrical connection from the solenoid and see if there's any difference in how the engine runs. If the vanos solenoid is bad, rebuilding the vanos assy won't fix anything.
Do you know where that's located? I just ran outside and did a quick check but didn't see any wires coming from the system (also couldn't locate the solenoid, though).

UPDATE Unplugged the solenoid and there was no difference at all. Still have no power at 3k. If I'm understanding this properly, this means that it's most likely a faulty solenoid, correct? With the solenoid plugged in, I have no power and a misfire at 3k. With it not plugged in, I still have no power and a misfire at 3k. This means the solenoid is faulty, right?

Also, no CEL even with the solenoid unplugged.
 

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Do you know where that's located? I just ran outside and did a quick check but didn't see any wires coming from the system (also couldn't locate the solenoid, though).

UPDATE Unplugged the solenoid and there was no difference at all. Still have no power at 3k. If I'm understanding this properly, this means that it's most likely a faulty solenoid, correct? With the solenoid plugged in, I have no power and a misfire at 3k. With it not plugged in, I still have no power and a misfire at 3k. This means the solenoid is faulty, right?

Also, no CEL even with the solenoid unplugged.
The problem with VANOS is not the solenoid but the VANOS seals, the solenoid activates but since the seals no longer work the oil does not build pressure to engage the VANOS. You can try redoing the seals yourself or buy a complete unit from Dr. VANOS.
 
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