Continuing Issues with the 540i- New Rough idle/start on cold engine

My last thread was related to a noise I began experiencing on a warm engine. Eventually, it was narrowed down to the VANOS units and I still think this is the case.

I am experiencing some new issues and I was hoping the forums could help me shed some light on them.

I typically get a rough start/idle when the engine is cold. It's accompanied by a sound that I can only describe as a bird chirp every second or so. When the engine warms up, even slightly, the idle becomes much more smooth. I also still get the cold start clatter every 5th startup or so even after replacing the chain tensioner.

I was hoping that in conjunction with the VANOS issue, these new problems could help describe what the problem may be. If they are all related to the VANOS issue, I will continue to wait until Besian systems has a working repair for the 540i. Until then, I suppose I can only hope for the best.

Anyone have any ideas?

Any codes you care to share?

None. No codes are showing. It's throwing me for a loop. No CEL, nothing.

Are you verifying the codes with a reader or relying on the CEL? The reason I point to this is because with 30 posts it appears the car is relatively new to you? Many 'dealers' especially 2nd hand dealers find it easier to remove the bulb for the CEL than to resolve issues...so while you have no CEL, you may have codes coming out the kazoo from the computer and based on what I know I'd say that is probably the case here...not 100% sure though...but seems logical enough.

Admittedly, I am relying on the CEL. Based on the reading I've done, I've been under the impression that the CEL goes off for ANY problems. The only exception to this (on my car) is a PowerChip that's been installed with Euro SAP software to remove SAP errors. I may be totally wrong and if that's the case, please advise as to where I could get the codes read. For example, coming from the Jeep community I could stop at any Autozone or Advance Auto and get my codes read. Is the same true for the BMW? Furthermore, I have confirmed that the CEL is working, it lights when the key is in the run position.

I purchased the 540i from another respected forum member some time ago, not a dealer. However, the car and the BMW community as a whole are very new to me. I came from Jeeps. This is a drastic departure.

So some additional observations.

The rough idle continues through the RPM band to the 2.5 mark when I rev it within the first minute of starting ( I haven't taken it above 2.5K so I can't confirm anything higher).

After about 1 minute of running, the engine quiets up substantially. I notice it when the door is open and I'm listening to the engine after just being started and not moving. It seems as if something turns off and then things sound normal. Although, the rough idle is still there however much more faint.

Finally, the problems of rough idle seem to occur more frequently on days with temperature variation. Cool mornings, hot afternoons (68-74F mornings and 86-96F afternoons).

Does this help anymore?

Confirmed this afternoon. No codes with a reader either.

I've been told that you might not have a light on, but there are codes being stored...

So could these also be symptoms of a VANOS issue? If so, what are my options for repairing the VANOS?

First of all the light only comes on for emissions related problems. More of a motor vehicle inspection thing. So there can be codes without it.


Sounds like you may have a vac leak in a intake related gasket. As the car warms the gaskets swells and the leak goes away.

Thanks for the information regarding the CEL light. I will keep this in mind for the future. I got it checked last Friday and saw the machine list no codes.

Additionally, thanks for the remark regarding the intake gaskets. Could you suggest some places to look? I'm not even sure where to begin.

One trick is, while the car is still cold and therefore leaking still, spray various areas with brake cleaner and you will hear the idle jump when u hit the right spot. Try the elbow, both ends of the maf, ,around the throttle body, the ccv, unfortuneatley the gaskets for the ports are hard to reach but thats where mine was.
I didnt even realize i had a leak. When its in the elbow the leak will go to all cylindersequally, when its in a port gasket only that one cylinder will run funny.
I noticed that when my hand was lightly touching the gearshift know in nuetral at idle that the vibration had an out of rhytim kick to it.
After doing my m60 intake manifold swap with all new gaskets i notice that i not only got slightly better mpg but the vibration in the shift knob is smoother. I assume t his was a leak and not better due to the swap. Technically the swap itself should not affect idling, if so, possibly should have made it worse since its not meant to be there. I deduce this means only one cylinder was leaking and causing the kick in the vibration. Besides the fact i could see the pattern of black crap on the cylinder head around that gasket after i pulled it off.

I will post some pics and diagrams in a few moments.

Excellent. I look forward to it. This could be the cause of what I think is a rough idle at times as well.

http://realoem.com/bmw/showparts.do?...81&hg=11&fg=40
number 14 is the port gasket. its the only gasket that makes sense that would cause a leak in only one cylinder therefore the kick in the rythim at idle. anywhere else the leak would go to all cylinders and be read at a lean cylnder/s bank. this shows the port, there are four of them. two cylinders per gasket. it also shows the profile gasket on the front and rear "caps" of the manifold.




http://realoem.com/bmw/showparts.do?...75&hg=11&fg=45
this is the brake booster lines. these run on vacuum power so they could also be the problem. i replaced all the crimped on clamps with regular hose clamps before i ended buying new hoses anyway.


http://realoem.com/bmw/showparts.do?...87&hg=11&fg=45
these are the vac line to the secondary air pump that will most likely be dryrotted.



to make the hunt even harder, an oil leak could potentialy be a vac leak since the crankcase is under vacuum from the osv/ccv.

o btw if you order gaskets there is one not in the pics. there is a throttle body to throttle body spacer gasket beside the throttle body spacer to manifold gasket in pic #1

damn found another potential, secondary air pipe o-rings
http://realoem.com/bmw/showparts.do?...85&hg=11&fg=50

You may want to take a look at the secondary air pump hoses the one from the pump under the fender becomes brittle and cracks, also just for grins, clean your MAF with MAF cleaner...just a few ideas for ya...GL

Forgot to mention this because im a diy'er and rarely goto the garage but a good garage should have the equipment to pump smoke thru your engine to easily visualize any leaks. This may be your best bet instead of randomly replacing everything.

Thanks for all the help Topaz. I had some time for a quick inspection yesterday and noticed that the brake booster line (#6 in post 14) wasn't properly seated. I fixed it and it seems to be better now, slightly. I believe there is another leak. I'll follow up with another look.

How long should the SAP run and how loud should it be? I noticed it was creating a lot of noise yesterday at startup.

Originally Posted by Florida540

Thanks for all the help Topaz. I had some time for a quick inspection yesterday and noticed that the brake booster line (#6 in post 14) wasn't properly seated. I fixed it and it seems to be better now, slightly. I believe there is another leak. I'll follow up with another look.

How long should the SAP run and how loud should it be? I noticed it was creating a lot of noise yesterday at startup.

SAP ususally only runs for about 60-90 secs when cold. After warming up it might not even kick on. If your hearing a noise during this time it's most likely the bearing going up in the SAP. CN90 has a write up posted explaining how to replace if your ambitious enough.

I dnt know much about the sap but, about leaks:
The maf calculates air flow to determine how much fuel to inject to keep the proper air/fuel ratio. Any leak behind the maf as almost all are, will not be calculated and erefore have an incorrect mixture ratio. Sometime you gotta put some miles on it for the comp to adjust if you got it fixed. This will cause a delay and make you wonder if you got it or not until about 3 days later as you slowly forget it ever happened. So just keep that in mind.

Everytime i repair my car or change a sensor i notice my mpg is out of whack if i reset it for about three days until it slowly goes back to normal.
With a vac leak you might experience 1 or 2 mpg increase now that its fixed.

Topaz- sorry for the delay in my reply. I took some things apart in the engine bay several days ago. I checked all the items you've listed and double-checked to make sure their connections were sound. It seemed like some of them were loose and I've noticed a 1 MPG increase since the adjustment.

If you could take a look at part #7 on the SAP diagram, post #17. I noticed that the elbow on the left hand side, from the view of the diagram, has a crack in it. Possible vac leak here? Where could I find a new hose?