Rough Idle at Start Up, Stop Lights, etc

[VaTechZHP]

I've been having a consistent idling issue for a week or so now which I had originally attributed to a torn lower intake boot. After replacing both lower and upper boots, there was no change in the cars ability to hold a steady idle.

The car seems to let the rpms drop to around 500 and you can feel the car start to stumble and shake if you are sitting at a stoplight.

My mechanic said he noticed the tear in the boot, but also noticed my CCV was on its way out. Is it possible that the CCV is also contributing to this idle problem?

While replacing the lower boot, I pulled the ICV and cleaned it with MAF cleaner. Does the ICV really only assist on cold start ups to adjust idle until the car warms up enough to idle unassisted? Could the ICV be the culprit of this erratic idle?

While the revs seem to dip down to 500 or so, the car will then compensate and rev up to almost 1500, smooth back down to around 7/800, then dip to 500, and repeat this process. The car almost feels like it is going to stall, but then catches itself.

I have not noticed any driving issues once the car gets going except that the pedal seems very twitchy in that if I lift off throttle to coast, the car will buck slightly as if I completely got off throttle after going WOT.

The CEL is on, and I had the codes pulled at Advance and they seemed to point to lean conditions which would make sense if I was sucking in unregistered air into the A/F mix.

Any thoughts would be great before I throw more parts at the car.

TIA!

[HokieZHP]

My car does this too to some effect. It will drop to about 500 then spring up to 1000-1200 then settle again. My CEL is not on though. It happens very rarely so I haven't bothered with it but I'm also interested in what you all think it is.

[aurelius]

What is the fault code number?

[danewilson77]

ICV or vacuum leak. Code will be helpful. Could be a myriad of things.

[VaTechZHP]

I'll have to dig through the car again and see, luckily the CEL is still on (not like its a good thing haha) so I could get the codes pulled again if I can't find them.

[Oli77]

About your question on the ICV and cold start ups only.

I can tell you this, I recently cleaned my ICV because I was having similar issues all though the changes in rmp where not as drastic as yours. Mine would simply dip low when coming to neutral (stop).

On startsup, mine would go high, then low then steady (on rmp) nearly all the time.

On cleaning the ICV, I noticed nearly 90% of starts are now high and then quickly and steady down to middle rmp speed (cleaaaaaannnn).

Cleaning the ICV also significantly reduced the number of instances when idle would dip too low on coming to a complete stop by 80%.

Perhaps a more thorough cleaning would get it perfect.

I have 75K miles and its all original stuff.

[danewilson77]

Even if light goes out...code will be stored.

[VaTechZHP]

Thanks Oli, I just sprayed some maf cleaner in there. I'll pull it back out and clean it with some Brake Clean and see if that helps. It certainly looked dirty in there when I pulled it out.

[3ZHP]

I had a similar problem last month and took it to the experts at Ganley BMW. It turned out to be a DISA valve. This is the rectangular box attached to the intake behind the dip stick. The tech notes stated that it had fallen apart and the parts were sitting in the intake "NOT A GOOD THING". The OEM part was $250.00 and all total my bill was over five with a few other thing included.

In looking on the net after I paid the price, I checked YouTube and the job looks simple as long as you know what your looking for. For more information Google BMW DISA.

[danewilson77]

Yes. Simple.

Sent from SIGFest-2012, USA on HTC via TTv2

[llll1l1ll]

So long as you can finagle the intake boot out of the way, it is literally a bolt-off, bolt-on procedure.

[VaTechZHP]

I just had the DISA off when changing out the lower intake boot. Very simple to replace. Would there be a way to determine if this issue is either the DISA or the ICV? As much as I love throwing parts at the car, I'd rather throw the right on haha.

[danewilson77]

I just had the DISA off when changing out the lower intake boot. Very simple to replace. Would there be a way to determine if this issue is either the DISA or the ICV? As much as I love throwing parts at the car, I'd rather throw the right on haha.

If you pull the DISA out, it will be apparent, whether or not this part is bad.

Sent from SIGFest-2012, USA on HTC via TTv2

[VaTechZHP]

Thanks Dane, I had never seen one before I pulled mine out of the intake. It looked in tact, a bit dirty, but all of the pieces were there. I'm going to pull it back out as I could get a replacement for around $300...I'm going to pick up a new ICV and try that to see if it helps after thoroughly cleaning the ICV in the car.

I'll try to get the codes as well once I get everything back together.

[Oli77]

I will be interested to know if a new ICV clean up that idle bounce.

Also, about the DISA (yes its dirty in there) and the flap should not easily move, there should be a good bit of resistance on it.

[aurelius]

How are you guys accessing the ICV so easily?

I cleaned my DISA and shored up the gasket with electrical tape easily enough but the lower intake boot's 2 hose clamps are facing away and down. While it is theoretically possible to get a small screwdriver down there, it is not a realistic procedure due to having so little room to maneuver, not to mention zero visibility of the screw heads on the clamps. The only solution seems to be to get a new lower boot and then rip the old one out with box cutters, then hope I can access the clamps.

Thoughts?

Meantime, click HERE (http://dl.dropbox.com/u/17676561/BMW%20docs/SIB%2012%2008%2005%20%28O2%20sensor%20codes%29.pdf ) to read a service information bulletin from 2005 that may be related to this topic (02 sensor codes).

[Oli77]

No screwdriver.

This: http://s.shld.net/is/image/Sears/00947235000-1

Mine has an angle on the closed end and it works like a charm.

[aurelius]

Thanks. I have that exact wrench set, I'll give it a shot.

I have a mild RPM dip at idle. Hasn't ever stalled and idle never rises above the usual level, with the exception of the usual higher idle on cold starts.

Curious to see how the ICV looks. 65k miles.

[danewilson77]

This is the exact lil sheet I use right here.....and it's the only thing I use it for. Sometimes a flexdrive screwdriver will help as well.

http://i1015.photobucket.com/albums/af278/nicee46/Maintenance%20and%20Misc/IMG_20110306_124420.jpg

[Oli77]

Curious to see how the ICV looks. 65k miles.

Here it is at 76 K:

Before

http://i900.photobucket.com/albums/ac208/othibau/DSC07189.jpg

After :

http://i900.photobucket.com/albums/ac208/othibau/DSC07190.jpg

[danewilson77]

You can see where the valve disc was dragging on the seat.

[Oli77]

Exactamundo. No seat draggin' allowed. nono

[VaTechZHP]

So are you going to replace it? I'm in the process of working on mine, but came across a busted DISA...unfortunately, the much more expensive part of the two to replace!

http://i43.photobucket.com/albums/e388/andrewelmore/IMAG0290.jpg

http://i43.photobucket.com/albums/e388/andrewelmore/IMAG0289.jpg

Since I've gone this far, I might as well pull the ICV out and clean that since I'm half way there at this point. I'll try to pick up the DISA today and see if that eliminates my idle issue.

[llll1l1ll]

My DISA valve just went the way of the ghost the other day. The result is a pretty crappy idle at 500. It stutters a bit and shakes the car. It was also making a ton of noise. I suspect this is the cause of my rough idle, so I have a new one on the way.

It's not quite the same as the OP's problem of a rising and falling idle; however, if the new DISA fixes the problem, I'll post it here.

[Oli77]

VaTechZHP: your DISA is busted as in the flap moves around freely? Cleaning the ICV and a new DISA, your idle is going to be smooth (hopefully).

So if a DISA valve were not seated right, or were not in the right position or were loose, air could circulate in the manifold and affect idles you guys think?

[llll1l1ll]

I would think so. I was getting a lot of vacuum noise in the DISA valve area for a while and then when it broke there was a lot of vacuum noise.

[Newjack]

I would think so. I was getting a lot of vacuum noise in the DISA valve area for a while and then when it broke there was a lot of vacuum noise.

This vacuum noise your mention. Does it sound like a whistling noise? With the windows down, I can hear a whistling noise when depressing the gas pedal.

If 100% is mashing the pedal to the floor and 0% is not touching it at all, the noise happens between the 55%-80% range. Regardless of speed, gear, or slope.

[VaTechZHP]

I was getting a fair amount of vacuum noise from the DISA area as well before I found that mine was broke. It sounded very much like a hose had been disconnected. I guess it was letting a lot of air move around in the manifold that wasn't supposed to be doing that. I'll have the replacement part back on later this afternoon/early evening so I'll see if that solves the problem. Shouldn't take long at all, so hopefully this cures the issue!

[aurelius]

Everyone should inspect the DISA for both the free play on the flap (it should move but with a fair amount of resistance) and also to check degradation of the base gasket material where it connects to the intake. Gasket can be shored up with electrical tape. Click HERE (http://db.tt/um6Wb2AX) for info on how to do that -- it's quite easy.

If the flap is loose it'll eventually break apart and get sucked into the motor.

Also worth checking part number while the DISA is out. Updated part ends in 805. Let's see if anyone lucks out and discovers they have the new one.....

[Oli77]

^ yes I remember a picture with a totally different one (longer at least). Where is that post?

[zhp43867]

http://www.bimmerfest.com/forums/attachment.php?attachmentid=294847&stc=1&d=1317099885

[Newjack]

7 544 805 is the good part. For those of you who almost broke your neck. Thanks for the part # Derek.

[VaTechZHP]

I ended up with the above part. Just got it reinstalled and the car is idling like a champ. I also cleaned out the ICV and replaced the lower and upper intake boots as well.

Car seems to be running fine, but havent driven it yet. Tomorrow i will pull the CEL codes and have them cleared to see what is next on the maintenance list.

[Oli77]

Good news.

[llll1l1ll]

This vacuum noise your mention. Does it sound like a whistling noise? With the windows down, I can hear a whistling noise when depressing the gas pedal.

If 100% is mashing the pedal to the floor and 0% is not touching it at all, the noise happens between the 55%-80% range. Regardless of speed, gear, or slope.

When I had the whistling noise, it was a tear in the elbow of the lower intake boot. It happened at the same throttle positions you described. That noise was annoying since I could hear it (I'm lame and drive with the radio off a lot). The vacuum noise I'm talking about now comes from the DISA valve area and is like, "sssssssshhhhhhhhhhooooooooooccccccckkkkkkk." It sounds as if I literally pulled a vacuum hose off somewhere.

My new DISA will be here tomorrow. I'm also mad now because I bought the Torx bits only to notice that the DISA has a normal hex bolt on there. Dang it!

[VaTechZHP]

My DISA had torx bolts, which I think it is supposed to have. I guess someone lost one at some point along the way?

[danewilson77]

My DISA had torx bolts, which I think it is supposed to have. I guess someone lost one at some point along the way?

Yeah. Supposed to be T40's

Sent from SIGFest-2012, USA on HTC via TTv2

[llll1l1ll]

I think someone did lose them... Haha

[aurelius]

I ended up with the above part. Just got it reinstalled and the car is idling like a champ. I also cleaned out the ICV and replaced the lower and upper intake boots as well.

Did you do these things one at a time such that you could vouch for which one solved your idle issue?

[llll1l1ll]

I just replaced my DISA valve and my car doesn't idle like crap any longer. It's nice and smooth. When my DISA valve was broken, it would more or less misfire/skip at idle.

[VaTechZHP]

I can't vouch for the cleaner ICV, but I know for a fact my DISA valve was toast. I replaced that and the car is idling great again. I had small cracks in the lower intake boot as well, but the DISA was completely shot.

Regardless of fixing the other pieces, having that broken DISA made the car act the same.


Did you do these things one at a time such that you could vouch for which one solved your idle issue?

[M3TA5IN]

Funny I'm going through same exact issue with the jeep gc. Right as we were getting ready to sell it.

Pretty sure I have it narrowed down to bank 2 #1 O2 sensor, going to replace tonight.

[echo46]

In my opinion, if you are experiencing idle issues, you should methodically address easiest to hardest as follows:
1. Check for codes
2. Check upper and lower intake boots
3. Clean ICV
4. Clean MAF
5. Clean Throttle body
6. Check DISA for vacuum leaks and functionality
7. Check CCV and all its annoying hoses including oil stick tube
8. Check fuel pressure at the rail
9. Check fuel lines for small leaks.
10. Check Fuel injectors for O-Ring leakage or injector leakage.

Can't think of anything else but if I miised something the experts will chime in.

[danewilson77]

Yup. And 1-6 should be done together imho.

Sent from SIGFest 2012

[echo46]

As long as you have everything off for 1-6, you should check CCV for leaks and the infamous OFHG for leakage. It just never ends.

[MrMaico]

This is a good thread about one specific CCV hose that can cause idle problems and certain codes. Good info to bookmark.....

http://forum.e46fanatics.com/showthread.php?t=773551

And another good thread with lots of info......

http://forum.e46fanatics.com/showthread.php?t=897616&highlight=50

[Oli77]

^ good stuff indeed. Thanks.

[aurelius]

There's a LINK TO DISA O-RINGS (http://germanautosolutions.com/DISA_O-Rings.html) in that 2nd e46f thread posted above. Read the DISA sub-section in that post and if you think yours is still good (after removal, inspection, shaking it, etc.), consider a new o-ring. I did the electrical tape thing but I'd prefer to have a proper seal in place to avoid any vac leak.

[echo46]

I too did the electrical tape half asser, just for some assurance eventhough I don't think mine was leaking. WIth the electrical tape it does fit in there nice and tight. Should probably just get a new O-Ring.

[danewilson77]

There's a LINK TO DISA O-RINGS (http://germanautosolutions.com/DISA_O-Rings.html) in that 2nd thread posted above. Read the DISA sub-section in that post and if you think yours is still good (after removal, inspection, shaking it, etc.), consider a new o-ring. I did the electrical tape thing but I'd prefer to have a proper seal in place to avoid any vac leak.

I put this in my diy thread. Thanks brah.

Sent from SIGFest 2012