Need some diagnostic help: hissing/whining under light accel, jumpy idle at start

[jeebus87]

Hey guys,

I have some issues with my si coupe. There is a very noticeable hissing/wind rush noise when I'm accelerating lightly. It only happens when I'm in drive, meaning that I can't replicate it in neutral in my garage. The sound is totally dependent on throttle position such that the noise is most obvious at 10-15% throttle and goes away as I floor it.

My indy found a really small leak in the resonator boot so we are replacing that, but he was skeptical it was the cause of the problem (they were able to replicate the noise). Any ideas what else it could be?

Also, I have a jumpy idle. When I start the car, lately, it's been having a bit of trouble firing and when it does the RPMs bounce between 900 and 1500. Any idea what that could be? Could the two issues be related? I am wondering if one of the DISA adjuster valves is gone...

I just found out I still have CPO, but I would like to diagnose on my own instead of going back and forth with the dealer. Thanks!

[Incompatible]

Sounds like a vaccum leak that you have not found.

[jeebus87]

So my indy did a smoke test, and only found that small leak near the resonator. Would the smoke test rule out any other vacuum leaks?

[jeebus87]

welp, the resonator boot was replaced and the noise persists. took it to the bmw dealer as i still have CPO and they said "it's a normal sound." definitely doesn't SOUND normal, but whatever. i guess it isn't getting worse and there is no CEL.

also, i noted to the dealer that one of my radio preset buttons was not working... they quoted me 1,000.57 for that repair. for one bad button! i thought they misplaced the decimal!

[Incompatible]

Hook up with other Z4 owners in your area and listen to their cars, then decide if yours is normal or not.

[jeebus87]

Originally Posted by Incompatible

Hook up with other Z4 owners in your area and listen to their cars, then decide if yours is normal or not.

Good point!

Any DFW Z4 3.0si drivers willing to help me out?? There's a 6-pack of your choice in it for you.

[R1robot]

Originally Posted by jeebus87

welp, the resonator boot was replaced and the noise persists. took it to the bmw dealer as i still have CPO and they said "it's a normal sound." definitely doesn't SOUND normal, but whatever. i guess it isn't getting worse and there is no CEL.

also, i noted to the dealer that one of my radio preset buttons was not working... they quoted me 1,000.57 for that repair. for one bad button! i thought they misplaced the decimal!

No, it is not normal. Mine did not make that noise until after the engine bay was washed (it was pretty dirty and i'm anal even about a dirty engine bay). After the wash, it would make that whining noise at idle. I could not locate the sound. I was not able to locate the sound when i popped the hood but it was obvious in the trunk and inside the cabin. I have heard problems with the gas pump but i don't see the relation as i only washed the engine bay.

After a week, it started to produce that sound when i hit the 1200- 1500 RPM mark in any gear.

I suggest you find a reputable bmw indy shop that takes warranty claims. Currently, my Z4 is going through a major inspection 2.

Or if you or a buddy that has a car lift can produce that sound and try to locate where it comes from while its up on stands you'll have better luck.

[partlowr]

Mine whistles ever since I installed my AFE intake

[ghrup09]

Same noise here, exactly as you mentioned.

[SF-Z4_3.0si]

Glad I'm not the only one with the whirling noise problem at low RPMs. With my car I only hear it with the top up inside the cabin.
I'd like to know if anyone finds the issue. I'll be taking my car in for other service to a friend, I'd like to add this to the list of repairs.

[ghrup09]

Yup I hear it at low rpms as well and only with top up. In addition, my idle rpm jumps from 600-800 rpm at initial start up after a few seconds before it settles at 550-600rpm. I have heard of everything from idler control valve, to maf sensor to the battery on this type of thread. May just need to take it to an Indy shop soon myself. As for firing issues, I recently changed out my original battery with a new one and haven't had any cold crank issues since. It definitely helped on initial startup. Definitely would like to close the loop on this issue soon. If anyone has more info, please pass the knowledge around on this one. It would be greatly appreciated.

[jeebus87]

Originally Posted by ghrup09

Yup I hear it at low rpms as well and only with top up. In addition, my idle rpm jumps from 600-800 rpm at initial start up after a few seconds before it settles at 550-600rpm. I have heard of everything from idler control valve, to maf sensor to the battery on this type of thread. May just need to take it to an Indy shop soon myself. As for firing issues, I recently changed out my original battery with a new one and haven't had any cold crank issues since. It definitely helped on initial startup. Definitely would like to close the loop on this issue soon. If anyone has more info, please pass the knowledge around on this one. It would be greatly appreciated.

I'll probably take mine in for a brake fluid flush in the next couple weeks and I'll ask my Indy to check the intake again, and to look at the DISA valves. Although with the refresh models I haven't heard of those going bad like they do on the M54.

I replaced my battery last week as well and my cold crank issues went away, and the idle has been a lot steadier - i.e. no more bouncing up to 1500rpm, just the regular 600-800 like you describe.

[jeebus87]

I'm thinking of replacing all the intake hoses. Can anyone help me out with part numbers? I'll order 'em and report back once replaced.

[Zfix]

Hi all together,

I´m experiencing the exact same problem with my z4 3.0si coupe.
Just to verify I´m talking about the same hissing sound - here is a thread where a video/soundfile is posted, that is the exact noise:
http://www.bimmerfest.com/forums/sho...409&highlight=

Has anyone figured out where it does come from / been able to fix it?
Any help would be greatly appreciated!

Zfix

[KevsZ4]

For what its worth,

I had the idle issue as well on my 2003 3.0

I know there were changes to some of the intake parts on the e86's, but it can't hurt to spend a half hour to check out the DISA and ICV.

In my case, they were both part of them problem. The ICV was clogged stuck with carbon buildup, and the DISA's plastic flapper and crank were worn down and not working at all.

It only took about 30 minutes to disassemble the intake to get to the parts. Pretty easy wrenching though. and putting it back together was even easier. (once I had cleaned the ICV and bought and installed the DISA repair kit)



Good place to start.

[Zfix]

Hey Kev,
thanks for your reply! Did you have the exact same noise on your 3.0 like in the video/Soundfile I posted? Or just the idle issue?
The E86 3.0si does not have a classic idle control valve anymore.

[KevsZ4]

No, I didnt have a noise like that. sorry