# Pulsing Idle / Car revs itself at start up



## DG7Projects (Jul 12, 2011)

I'm in a 2006 3.2 (40K miles) and my car will sometimes act strangely upon start up. The idle pulses up and down, like it's mildly revving itself. This doesn't happen at cold start. It happens maybe during the 2nd start up of the day (coming home from work) and it's only happened to me twice at 6 week intervals. (no codes at scan)

EDIT: Forgot to mention that this pulsing goes away as soon as I switch the shifter away from Park. 

Has this happened to any of you 3.2 guys? It's the first time I've experienced this in a long history of owning VR6 equipped cars. 

I'm getting a bunch of service done this Friday, but I'm hoping you gents can chime in and I could advise my tech on what to look out for. Thanks in advance. I'll buy you a case of beer if your suggestion is spot on. :laugh: :beer:


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## MisterJJ (Jul 28, 2005)

I was all ready to ask if you've done the PCV recalls when I saw "3.2".

I'm still thinking it's a PCV problem though. Or some vacuum leak. Oil cap leak, maybe.


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## ceese (Jul 2, 2011)

DG7Projects said:


> I'm in a 2006 3.2 (40K miles) and my car will sometimes act strangely upon start up. The idle pulses up and down, like it's mildly revving itself. This doesn't happen at cold start. It happens maybe during the 2nd start up of the day (coming home from work) and it's only happened to me twice at 6 week intervals. (no codes at scan)
> 
> EDIT: Forgot to mention that this pulsing goes away as soon as I switch the shifter away from Park.
> 
> ...


My car does that as well - I've never worried about it though. It's subtle but you can feel it throughout the car.


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## Ponto (Jan 11, 2012)

ceese said:


> My car does that as well - I've never worried about it though. It's subtle but you can feel it throughout the car.


Sounds to me similar to a cold start high idle? However it should usually be smooth and not pulse...


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## neu318 (Feb 18, 2003)

Some people over in the R32 forum have mentioned a similar issue and a few of them have had it resolved by changing their battery. I know it sounds weird but they said something like the car not getting enough voltage or dropping voltage which causes the car to pulse a little.


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## SilverSquirrel (Jul 24, 2006)

hunting idle in closed loop can be a sign of an oxygen sensor going bad. You may not get a CEL (yellow light on dash) but a scan for codes can show faults that have been recorded.

You can also use vag com to log all 4 oxygen sensor signals along with rpm to diagnose.


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## DG7Projects (Jul 12, 2011)

Thanks gentlemen. I'll be dropping the car off tomorrow and will have the shop look into it. For the record, that pulsing idle /self revving happened once more. :facepalm:

So as of now, it's *neu318*, *MisterJJ*, & *SilverSquirrel's* suggestions that would yield one of them a case of beer. I'm leaning towards *neu318's* suggestion. 

I'll check back in on Saturday with results. Thanks again guys. :thumbup::beer:

EDIT: Let's add *Ponto* to that list!


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## Ponto (Jan 11, 2012)

One other thing it could be, is the MAF... When cold it can cause issues with idle (if its failing) and then once warm be fine. Had that issue before with other cars. 

Good luck with fixing it!


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## neu318 (Feb 18, 2003)

DG7Projects said:


> Thanks gentlemen. I'll be dropping the car off tomorrow and will have the shop look into it. For the record, that pulsing idle /self revving happened once more. :facepalm:
> 
> So as of now, it's *neu318*, *MisterJJ*, & *SilverSquirrel's* suggestions that would yield one of them a case of beer. I'm leaning towards *neu318's* suggestion.
> 
> I'll check back in on Saturday with results. Thanks again guys. :thumbup::beer:


Keep us posted. I have the same problem and want to get it fixed.


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## DG7Projects (Jul 12, 2011)

Ponto said:


> One other thing it could be, is the MAF... When cold it can cause issues with idle (if its failing) and then once warm be fine. Had that issue before with other cars.
> 
> Good luck with fixing it!


Thanks for that. It's worth looking into. How's the 3.2q in the snow? 



neu318 said:


> Keep us posted. I have the same problem and want to get it fixed.


Will do. If you don't mind me asking, how often does this happen to your car?


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## neu318 (Feb 18, 2003)

It doesn't happen too often. It happens while at idle. Very randomly.


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## Grey D (Mar 3, 2009)

coming up on 50k miles... My car has been doing this as long as I can remember, well, I had an O2 sensor go bad so that's going to be replaced, i'll let you know if it also resolves the idle issue. Though, it's not so much a wandering idle, it just kicks up a little and hangs for awhile.

My car is catless and tuned though, so running rich while i wait for this sensor has been a little fun with all the firebreathing :laugh:


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## Travis Grundke (May 26, 1999)

Grey D said:


> coming up on 50k miles... My car has been doing this as long as I can remember, well, I had an O2 sensor go bad so that's going to be replaced, i'll let you know if it also resolves the idle issue. Though, it's not so much a wandering idle, it just kicks up a little and hangs for awhile.
> 
> My car is catless and tuned though, so running rich while i wait for this sensor has been a little fun with all the firebreathing :laugh:


Exact same problem I have on my '06 2.0T: it will kick up and hold for anywhere between 5-15 seconds, then drop down to idle. I've got a P0171 code getting tossed consistently. Everything I've read points to a vac leak somewhere, but I haven't the faintest clue as to how best to start troubleshooting that puppy.

I'll be interested to hear what you find as well!


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## DG7Projects (Jul 12, 2011)

Took car in for 45k, DSG, Haldex service, brakes, etc... 

Checked out MAF, scanned for codes, checked for vacuum leaks, checked battery & voltage, & no joy. Nothing found. The car does run smoother than it did before I took her in. The previous owner wasn't that meticulous with service. (found a super brittle, wafer-like oil filter) 

Anyway, if this pulsing happens again, I'd have to hunt for more solutions. Thanks again for those suggestions. :thumbup:


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## Ponto (Jan 11, 2012)

Glad to hear it's running better. Never thought of just maybe needing a little love. The Quattro is amazing in the snow we have the over a foot and a bit now. 

Sent from my SGH-I757M using Tapatalk 2


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## SilverSquirrel (Jul 24, 2006)

Ponto said:


> .....we have the over a foot and a bit now.
> 
> Sent from my SGH-I757M using Tapatalk 2


Better you than me, pal!

:what:but my blizzaks, jack, and torque wrench are front and center in the garage


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## DG7Projects (Jul 12, 2011)

Ponto said:


> Glad to hear it's running better. Never thought of just maybe needing a little love. The Quattro is amazing in the snow we have the over a foot and a bit now.
> 
> Sent from my SGH-I757M using Tapatalk 2


Say Ponto, I was wondering if you could kindly take a pic of your trunk area for me (at your earliest convenience) . Specifically the area under the mat (tools, battery, etc...) The PO changed things up in the boot to fit an aftermarket stereo but failed to return the trunk to it's original state. I'm now hunting down parts, & tools for the trunk, but need a picture for reference. For the record, I have zero tools, I do not have the original trunk floor, and am missing the driver's side panel that houses the trunk light.


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## Ponto (Jan 11, 2012)

You bet man will do it tomorrow morning. 

Sent from my SGH-I757M using Tapatalk 2


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## DG7Projects (Jul 12, 2011)

Ponto said:


> You bet man will do it tomorrow morning.


Thanks! I truly appreciate it. eace:


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## everfresh59 (Jul 26, 2010)

I've been having the same rough idle and just assumed its normal. The weather is getting colder and since I've been using the same Varta battery the car came with, I thought it was a good time to change it.

I went out and got me an Everstart Maxx battery from Wal-Mart. Since I had read online that most batteries are manufactured by Johnson controls, I didn't bother to try and look for a Bosch or any other brands that are normally recommended.

Battery came out and installed without issue, but when I first turned her one the idle was sporadic. I assumed the ECU was simply re-adapting, so I let her run like that for about 20-30 seconds and then turned her off. 

Once I turned her on for a second time, everything seemed normal, took for a quick spin and all the warnings and ESP lights shut off.

I'm gonna let her sit for the night and I. The morning I'll plug in vagcom and check for any errors. I'm hoping this fixes the rough idle from a cold start.

You guys think I just do a throttle body alignment? I'm running APR tune @ 93 program.


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## Travis Grundke (May 26, 1999)

Well, I think I found the source of the problem on my 2.0T last night. While checking the engine bay I found that the breather hose (not the tube on the back, the host which goes from the PCV to the intake manifold) had some oily residue on it. I checked to see if anything else around it was leaking but didn't see anything.

Upon closer examination I found a pinprick hole in the breather hose. I temporarily wrapped it with duct tape and voila - problem solved. Now I just need to replace the hose itself.


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## everfresh59 (Jul 26, 2010)

So this morning when I turned the car on from a cold start, rough idle seemed to have gone down slightly, but not enough to merit it the cause of the problem. I'll scan the car at lunch and see if it finds anything.




Travis Grundke said:


> Well, I think I found the source of the problem on my 2.0T last night. While checking the engine bay I found that the breather hose (not the tube on the back, the host which goes from the PCV to the intake manifold) had some oily residue on it. I checked to see if anything else around it was leaking but didn't see anything.
> 
> Upon closer examination I found a pinprick hole in the breather hose. I temporarily wrapped it with duct tape and voila - problem solved. Now I just need to replace the hose itself.



This is definitely what I'm going to try next.... I have a new breather tube which I haven't yet had the chance to install. I replaced my PCV and gasket in July, but never got around to swapping the breather tube. I'll probably do the N80 valve as well just for good measure. I just hope the warm weather holds up till next weekend.


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## Grey D (Mar 3, 2009)

well to update, I got the oxygen sensor replaced and the car is running normal AFRs now and is a lot more pleasant to drive... still does the raising idle thing though. I really think this is nothing to worry about as it raises to about 1050 and stays steady, i would be more considered if it was a "lingering" idle that was constantly going up and down


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