Mystery idle stumble

"If only EssExTee could be so grossly incandescent" (essextee) 01/21/2016 at 13:19 • Filed to: None

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Started a few days ago. Only happens when engine is idling & stone cold. Sometimes bad enough to stall. No codes in ECU. Any ideas? Car is a 2000 528i.

Dash-doorhandle-6 cyl none the richer > If only EssExTee could be so grossly incandescent 01/21/2016 at 13:26

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Intake Idle Air Control Valve?

HammerheadFistpunch > If only EssExTee could be so grossly incandescent 01/21/2016 at 13:27

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Whats your voltage like? If its cold and there is a lot of demand on the electrical system and load on the engine (cold start, warming fluids, running the AC for defrost, etc) then it can surge the engine a little at idle. Or, are you sure its the engine and not just the electronics (I can’t hear the engine in the clip...strange)

forgeryfade > If only EssExTee could be so grossly incandescent 01/21/2016 at 13:27

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Perhaps the EGR. They can typically be cleaned to rule it out or identify if it’s the problem. What kind of vihicle is this?

GMart > If only EssExTee could be so grossly incandescent 01/21/2016 at 13:30

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Sure seems like a vacuum leak of some kind.

Nibbles > Dash-doorhandle-6 cyl none the richer 01/21/2016 at 13:31

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What he said. My Saab does (did) the same exact thing because of a failing idle air controller. Come to think of it, so does the Dakota. Only on cold starts in the cold winter months.

crowmolly > If only EssExTee could be so grossly incandescent 01/21/2016 at 13:32

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Check your IAC valve. Scan it for position if you can.

Dash-doorhandle-6 cyl none the richer > Nibbles 01/21/2016 at 13:32

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Might just be ganky, and gank freezes.

If only EssExTee could be so grossly incandescent > HammerheadFistpunch 01/21/2016 at 13:33

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It’s called “sound insulation”. Also, “stereo speaker 1ft from phone”.

But yes, It’s not just the instruments. The engine itself is bouncing. It’s like it tries to correct itself, i.e. the revs start to drop so it adds more throttle, but then it goes over the correct idle speed so it cuts the fuel and then it drops below the idle point again, et al.

Have no volt gauge, will have to get back to you on that.

HammerheadFistpunch > If only EssExTee could be so grossly incandescent 01/21/2016 at 13:35

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More the second than the first, but I digress. Anyway, watch the volts, run your window switches when its cold too to look for sharp dips and or an effect on the idle. Might be an indicator of a bad battery or insufficient charging.

Bman76 (no it doesn't need a WS6 hood) M. Arch > If only EssExTee could be so grossly incandescent 01/21/2016 at 13:37

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EGR tube is a place to look, my TA had a leak which was causing vacuum issues.

Nibbles > Dash-doorhandle-6 cyl none the richer 01/21/2016 at 13:38

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Yup. I don’t know the specifics of his model. The controller in my Saab is rotary valve and the slightest bit of gank will fuck up the rotation. Regular cleaning is part of OG900 ownership.

If only EssExTee could be so grossly incandescent > GMart 01/21/2016 at 13:42

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It’s a modern engine, not a whole lot of vacuum operated stuff on it but I’ll check. Wouldn’t that cause isdues across the board though, not just when cold?

If only EssExTee could be so grossly incandescent > HammerheadFistpunch 01/21/2016 at 13:44

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Battery came with car, no clue how old it is. Could be culprit.

Santiago of Escuderia Boricua > If only EssExTee could be so grossly incandescent 01/21/2016 at 13:48

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No way!! My e36 was doing this yesterday! Hope you find a fix

Decay buys too many beaters > If only EssExTee could be so grossly incandescent 01/21/2016 at 13:49

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Hasn’t happened to my E39 yet, but I ran into a similar issue with my VW, turned out to be an intermittent Maf sensor (never threw a code mind you), not sure why it only happened cold, but I disconnected it entirely and the issue smoothed out. Replacement solved the issue and I never had a re-occurrence.

iSureWilll > If only EssExTee could be so grossly incandescent 01/21/2016 at 13:52

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Is this a 525? 530? 540? What model year?

My first guess would be a very small vacuum leak. When things warm up and expand a tad the leak goes away or is so small it makes no difference. I would THINK it would throw a lean code for this issue but it may be too small of a leak to detect.

If its a 540, possible places to look are at the front and back of the intake manifold. There is an o-ring style gasket on both ends that tends to leak over time.

If its a 525/530, then check all of the plastic stuff on the bottom of the intake manifold like where the PCV hose connects back to the intake tract.

You could try using some starter fluid spraying to see if you can find it.

If only EssExTee could be so grossly incandescent > Decay buys too many beaters 01/21/2016 at 13:54

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I will look into that.

If only EssExTee could be so grossly incandescent > iSureWilll 01/21/2016 at 13:56

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2000 528

iSureWilll > If only EssExTee could be so grossly incandescent 01/21/2016 at 14:00

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I would check all of the plastic stuff under the intake manifold. The PCV valve back to the oil separator and the plastic hoses under there. I’ve actually seen a 525 with a cracked valve cover as well. Lots of plastic on that engine to crack :)

GMart > If only EssExTee could be so grossly incandescent 01/21/2016 at 14:05

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The cold caused some issues with my X3, newer I6 than the M (S?) 50(52?) in that E36(?) The way it’s coughing and stumbling without throwing any codes or anything, it’s worth checking that the intake hose, after the MAF, isn’t cracked. In the X3, it’s a fat leak in the CCV valving that is causing vacuum leakage and near-stalling.

It’s one of those things to check over and rule out, ya know?

vicali > Decay buys too many beaters 01/21/2016 at 14:13

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I swiss cheesed my MkII airbox, then proceeded to drive it down the freeway at -40C. After the throttle plate unfroze(!) the engine did this, except up to 5000rpm- down to 500rpm, back up, down, up...

Parked it indoors and let it thaw out and it was happy. Got a winter airbox* for winter and it never happened again.

(*Winter airbox - put a screw in the hot air flap and leave the plumbing so the airbox pulls from near the header.)

If only EssExTee could be so grossly incandescent > GMart 01/21/2016 at 14:18

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M52TU E39.

Aaron M - MasoFiST > If only EssExTee could be so grossly incandescent 01/21/2016 at 14:25

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Sounds like either a vacuum leak or your idle control valve. Stolen from http://www.dvatp.com/bmw/icv_ccv :

“The ICV can become clogged with carbon deposits and fail to open and close smoothly. If this occurs the idle may oscillate. During more radical oscillations the engine can die. Unfortunately, these symptoms are also typical of vacuum leaks so in the event you lack access to a GT1 analyzer for a proper diagnosis the ICV should not be replaced until vacuum leaks have been eliminated as a possible cause.”

Highlander-Datsuns are Forever > If only EssExTee could be so grossly incandescent 01/21/2016 at 14:35

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I’d try an Italian tune up first.

If only EssExTee could be so grossly incandescent > Highlander-Datsuns are Forever 01/21/2016 at 14:37

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i do dat erryday

Santiago of Escuderia Boricua > If only EssExTee could be so grossly incandescent 01/21/2016 at 14:52

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Is that an M52? I think I have the same thing in my 99 e36 328is

If only EssExTee could be so grossly incandescent > Santiago of Escuderia Boricua 01/21/2016 at 14:56

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M52TU

RallyWrench > If only EssExTee could be so grossly incandescent 01/21/2016 at 14:56

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Start by checking the throttle housing for carbon deposits.

BLCKSTRM > If only EssExTee could be so grossly incandescent 01/21/2016 at 15:19

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It’s just one of those things.

Yeah, you may have a slight vacuum leak or something, or need to clean out your idle control valve. I mean, you have a healthy number of miles on there.

But it’s a fairly common thing guys complain about. There are books on bimmerforums just about this issue.

My M3 (98 w/ 202k) stumbles just a little when it’s “cold” (I’m in Texas, so it’s warmer than Idaho or Michigan on a July morning), but a little throttle for 30 seconds or so evens it out.

BLCKSTRM > If only EssExTee could be so grossly incandescent 01/21/2016 at 15:26

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There are vacuum lines all over - coming off the crank case, oil pan, throttle, intake boot, idle control valve, EGR valve, brake booster, oil separation valve under the intake manifold. In fact, there’s a giant rat’s nest under the intake manifold - vacuum lines, cooling lines, wires - you name it.

they-will-know-my-velocity > If only EssExTee could be so grossly incandescent 01/21/2016 at 18:49

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It seems like that it is fighting a low idle. I assume normal idle is around 800rpm? It’s dipping it to 300 or so and throttling up to keep it from dying.

ECU is probably working fine since it’s keeping it running. You may check your throttle body and see if you have excessive carbon buildup. Probably not the issue but I know my 4.6L 3v in my mustang would have a stumble that I could fix with a toothbrush and some TB cleaner.

Otherwise I suspect a leak or blockage. Check your air filter and look at your intake pipe to ensure it isn’t split. Fuel restriction would probably trip a code.

itranthelasttimeiparkedit > BLCKSTRM 01/21/2016 at 19:17

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Yeah, e39 has a shitload of vacuum everything, especially emissions related. I just had to do the valley pan gasket on 540i for a similar problem, I would start looking for cracks in hoses and the intake boot first, then probably go do a smoke test