# Weird problems with my Jetta



## jonfromnc (May 1, 2013)

*Weird idle problems with my Jetta*

I have a 2006 Jetta (manual). A few months ago, the car began to idle strangely. It seemed that whenever the car would warm up, it could no longer control idle. It would idle high, but then fall low, and idle high again, but usually stay high after coming to a stop. This would usually cause a check engine light to come on (but would turn off it it didn't idle for a while). Also, we only filled the tank when it got very low. When we did, a lot of times (not all the time) it would start, but immediately die, and then struggle to start again. When it did finally start, it would start as if it had flooded. It also did this one time when the gas was not low, around 1/4 tank. Then it miraculously stopped. 

Yesterday, when I went to lunch, I heard what sounded like a muted popping noise coming from the rear of the vehicle. Started like normal, drove back to work no problem. As I left work, I started it and drove about 20 yards, and it started making louder popping noises again from the rear. I stopped and let it sit, where it popped a little more, then started to idle rough. After starting it again, it idled exactly like it did before, with the high/wandering idle. The popping doesn't happen while I'm driving, but it does whenever I cut the car off. And the check engine light came on as I was driving to work (probably due to the wandering idle, since it came on at a stop light). The check engine light did not come on yesterday when the popping happened, or when the idle became rough. 

Any ideas as to what this could be? I'd like to get it fixed myself if possible obviously. It has NOT been through the major service components of the 60/80/100k maintenance, and it is at 100k miles, so my first thought was trash in the injectors, so change the fuel filter? Thanks for your help!


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## TrillyPop (Jan 27, 2010)

Pull the cel codes, that's where the answer might be hiding. I would also start with the simple things - clean MAF, check spark plugs, filters, oil. Try putting some better gas into it.


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## vdubtech398 (Jul 19, 2007)

Sounds like timing chain issues. Codes would help 


Sent from my iPhone using Tapatalk


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## xkRoWx (Feb 17, 2010)

Check your cooling system. You may have a faulty coolant temperature sensor or thermostat. The ECU will try to adjust fuel trim to engine operating temperature (cool engine, more fuel), thus the rough idle. 

Maybe check your air filter as well. 

The popping noise you're describing sound like the fuel pump that a few certified VW technicians told me, on my 2010 Golf it knocks once a while. I guess it's normal.. 

Nothing to do with your timing chain. :screwy:


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## Ferd Burfel (Feb 4, 2012)

jonfromnc said:


> I have a 2006 Jetta (manual). A few months ago, the car began to idle strangely. It seemed that whenever the car would warm up, it could no longer control idle. It would idle high, but then fall low, and idle high again, but usually stay high after coming to a stop. This would usually cause a check engine light to come on (but would turn off it it didn't idle for a while). Also, we only filled the tank when it got very low. When we did, a lot of times (not all the time) it would start, but immediately die, and then struggle to start again. When it did finally start, it would start as if it had flooded. It also did this one time when the gas was not low, around 1/4 tank. Then it miraculously stopped.
> 
> Yesterday, when I went to lunch, I heard what sounded like a muted popping noise coming from the rear of the vehicle. Started like normal, drove back to work no problem. As I left work, I started it and drove about 20 yards, and it started making louder popping noises again from the rear. I stopped and let it sit, where it popped a little more, then started to idle rough. After starting it again, it idled exactly like it did before, with the high/wandering idle. The popping doesn't happen while I'm driving, but it does whenever I cut the car off. And the check engine light came on as I was driving to work (probably due to the wandering idle, since it came on at a stop light). The check engine light did not come on yesterday when the popping happened, or when the idle became rough.
> 
> Any ideas as to what this could be? I'd like to get it fixed myself if possible obviously. It has NOT been through the major service components of the 60/80/100k maintenance, and it is at 100k miles, so my first thought was trash in the injectors, so change the fuel filter? Thanks for your help!


 The problem you are having is with something colloquially known as a Purge Valve or an N 80 valve. The problem is with the pressure in the system. The popping you are hearing is literally the pressure pushing on the gas cap. It'll probably get so bad your separate gas cap light will come on. 

The part itself is here at ECS tuning: http://www.ecstuning.com/Volkswagen-Jetta_V--2.5/Search/Purge_Valve/ 

Here is a crappy cell phone picture:








And another:









Once the valve was replaced my check engine lights and gas cap lights went away, and haven't returned after 400+ miles. The sounds you were hearing were the gas cap pushing out and the gas tank contorting behind the pressure. I replaced mine as part of the 80k service I just did, after I ran it down. This seems to be a common problem with a lot of Jettas. 

Hope this helps!


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## afawal2012 (Jan 9, 2013)

@Fred Burfel 

I hear the popping noise regularly with my MKVI Jetta. Is it a normal noise? I have not experienced driveability issues, nor do I get any CEL's. I've got about 35k miles on my car now.


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## Ferd Burfel (Feb 4, 2012)

afawal2012 said:


> @Fred Burfel
> 
> I hear the popping noise regularly with my MKVI Jetta. Is it a normal noise? I have not experienced driveability issues, nor do I get any CEL's. I've got about 35k miles on my car now.


 It depends on the particular popping noise. I'm by no means an expert, I only know all of this through the experience of my car. If the gas tank itself is popping or you can hear the pressure pushing on the gas cap you are definitely having a pressure issue. If the pop is so audible you can hear it, then there is something wrong. If your sound is coming from the tank and gas cap, I would replace it ASAP. 

With mine it was getting so bad it was starting to crinkle the gas tank, especially when my fuel levels were low. It doesn't appear to have caused any permanent damage I can find, but I can't know for sure yet. I was told the trick to testing the valve is to pull it off and try to blow through it. If air flows right through, the valve is shot. If you feel partial air, it's going bad. If you get no flow through simply by blowing, that's what it's supposed to do. My old one was wide open. The one I replaced it with allowed no air to pass through. This might be anecdotal, but it all seems to have been true and all my problems have been fixed.


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