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      03-12-2011, 02:45 PM   #1
elp_jc
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Is my idle valve starting to go? Engine almost stalling on 6MT

Hi gang. Wanted to start a new thread because all idle valve issues I've read here start with erratic idle (and I've been around for a while ), usually involving higher rpm. I made the title specific for future searches.

Just came back from another 800-mile trip, and other than a stupid falcon hitting my hood (fortunately nothing happened to it) and having a flat that forced me not to exceed 80 mph on the way back ('stop & go' tire repair kit worked great), all was well with the exception that in TWO occasions my engine wanted to stall (twice the second time), with the complimentary ugly noise and shaking. This is a 6MT, and it happened after pulling over from the highway for TPMS light and bathroom break (not low in gas). No problem with cold starts at all so far, which is usually the first symptom of a bad idle valve. I've done this run many times before, and only filled up at Chevron stations, with the exception of a few gallons of Texaco, but this was after the 2 incidents. I've always filled up at the stations in question, which are high-volume gas stations (I always fill up with Chevron whenever possible). Oh, and A/C off, so can't blame that.

Any ideas if we're dealing with the idle valve here? I just can't find an explanation of 'bad gas' causing just this issue, and just twice.

My questions are the following:

- Does a regular OBDII scanner would read codes related to the idle valve issue (misfires, IAP sensor, etc)? Remember reading that they don't read Motronic codes, but after checking what ECU we have, it turns out it's a SIEMENS, not Bosch. Is that also considered 'motronic'? I know car has several ECUs, so maybe others are Bosch Motronic. If somebody can enlighten me of the different ones and what they do, it'd be great .

- Has anybody changed the idle valve on their own? How much is it? Might have no choice but letting only local dealer fix it if too expensive (probably the case), but it's a small city, and according to my SA they never heard of idle valve problems, so I know it'd be an uphill battle to get this issue resolved. As most of you know, the stupid car diagnostics rarely points to the idle valve itself. Plus my car would have to throw some codes before I even bother to take the car in.

With so many dealer f**k ups recently, and not trusting only local dealer in town, I'd like opinions from DIYelfers on how to approach the issue if it worsens.

By the way, I tried to inspect the idle valve when car was new, but had to abort the job when I found special clamps on the hoses, since it'd had made it obvious I worked on the car if replaced. Thanks gang.
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      03-14-2011, 01:15 PM   #2
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Bumping my own thread in hopes people willing to help were idle over the weekend .

Just want to know from the experts what could be wrong with car almost stalling when hot at idle. Again, none of the myriad of idle valve issues showed this symptom first on 6MT cars. Remember reading something similar about an engine sensor, but spent hours reading searches in vain.

Problem is I use the car mostly for 800-mile trips in the middle of nowhere (little towns here and there), and want to know what I'm dealing with. I know the idle valve shouldn't leave me stranded after showing the 'christmas tree' on the dash for the first time, but an engine sensor might be a different story. Thanks.
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      03-14-2011, 01:34 PM   #3
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My 08 had the idle valve problem. It started at about 14,000 miles. On start up, all the lights would blink and it'd take 20 seconds to start. Then it'd run like it was on 4 cylinders. Reduced power, a bunch of warnings. Wish I still had the video.

It never stalled though.

Last edited by eluder; 03-14-2011 at 01:43 PM.
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      03-14-2011, 05:06 PM   #4
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Quote:
Originally Posted by eluder View Post
On start up, all the lights would blink and it'd take 20 seconds to start. Then it'd run like it was on 4 cylinders. Reduced power, a bunch of warnings. Wish I still had the video. It never stalled though.
Thanks for the help man, but I'm fully familiar with those symptoms. That's why I'm a bit baffled. My car didn't stall, but almost, in 2 different occasions. Took it out today to fill up the tank, and everything normal, like usual. I had A/C on though, but started up fine, and after arriving home let it idle for several minutes and no hiccups. Idle has always fluctuated a little since new after a few seconds (not perfectly steady, like mmmmmmMMMMmmmmmmmmMMMMmmmmmmm), from 550 to 600 or so. When A/C is on, it pretty much stays at 700 rpm (minimal fluctuation, but can still hear it), just like when you depress the clutch pedal.

One thing my car doesn't do anymore is the 'loud' start-up; it's quiet now. Another that I'm glad doesn't do anymore is the clutch/tranny 'clank' at start-up, which turned into a 'bang' if you released the clutch pedal right away. Now no clunk or pop at all. Wonder what it was. This is a weird car; that's all I know . Take care, and thanks again.
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      03-14-2011, 08:46 PM   #5
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Best of luck JC, can't help you but hope you get it resolved.
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      03-14-2011, 11:21 PM   #6
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Best of luck JC, can't help you but hope you get it resolved.
Thanks man. So far it looks like one of those one-time electronic gremlins I've gotten over the months (stereo blast, bluetooth error, no sound thru speakers at all -radio, nav, BT working, but no sound-, etc.), but mechanical gremlins scare me a lot more .

Hope it was fuel related, but just can't find a logical explanation (water in fuel, etc) for engine wanting to die just twice without other symptoms, and after filling up from large-volume Chevron stations. Oh well. At least engine didn't stall. Will borrow a friend's scanner, but it's a basic OBDII though. The good news is most engine codes affect emissions, so any misfire codes or the like should show up on that scanner. Thanks.
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      03-15-2011, 10:47 AM   #7
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before you go all out and think idle valves, it's more likely (and simpler) to assume vapor lock. your description of a hot engine after long drive and short stop to pee leads me to think it's clearing fuel vapor from the lines and settles after a minute or so of idling.

Last edited by OldenburgerM3; 03-15-2011 at 04:37 PM.
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      03-15-2011, 12:29 PM   #8
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just to chime in, i have a 6MT as well in my car, and she does that pretty often too... i havent paid attention if it happens more in certain conditions than others, but it seems to be a fairly common "issue" on our side of the internet forum world...
i dont think that helps, really, but i wouldnt go crazy about it just yet...
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      03-15-2011, 02:07 PM   #9
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Quote:
Originally Posted by OldenburgerM3 View Post
before you go all out and think idle valves, it's more likely (and simpler) to assume vapor lock.
I'm not going 'all out', so don't worry. Just wanted to know if the cause could be something that could leave me stranded, that's all. By the way, vapor lock is highly unlikely but possible, I guess; my question then is why it didn't happen before, with higher speeds and ambient temperatures?

Quote:
Originally Posted by frenchM3dreamer View Post
just to chime in, i have a 6MT as well in my car, and she does that pretty often too... i havent paid attention if it happens more in certain conditions than others, but it seems to be a fairly common "issue" on our side of the internet forum world...
i dont think that helps, really, but i wouldnt go crazy about it just yet...
Hey man, that HELPED A LOT, because at least I know it's something 'normal', as in the car shouldn't do it, but many do, with no problems (the M3 has a lot of weird traits like that, like clunking noises, etc). I've never read about that issue before, so I'm glad you chimed in for others who might experience it as well . I have to say it's possible my car has done this before, but never noticed it, since I usually have the stereo on, plus I'm not constantly glancing at the instruments for the TPMS symbol , like I was on this trip due to my plugged left rear tire.

Having said that, I'm curious what it is. I say it HAS to be the idle valve, but maybe it's just a peculiarity, and not an indication of impending failure. We'll see. Thanks again to all for your contribution. Have a great day.
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      03-15-2011, 02:26 PM   #10
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Not sure that this is any help as my car has an M-DCT which has a creep feature (that engages and disengages more or less on its own) meaning that the clutches are dragging some of the time that the car is stopped. I've noticed that my car idles much less smoothly when the AC is off than it does when it is on. It sounds and feels like it's loping a bit maybe even misfiring slightly.
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      03-15-2011, 03:47 PM   #11
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Quote:
Originally Posted by calintexas View Post
I've noticed that my car idles much less smoothly when the AC is off than it does when it is on.
Same here, I guess mostly due to rpm jumping to 700 with A/C on, rather than 550 or so. It's too darn low, especially for a high-revving NA motor, but engine is surprisingly smooth even at those low rpm IMO.
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