# Rough/Shaky Idle



## TimboAA (Sep 12, 2001)

The car:
2007 2.5L Manual Transmission Rabbit 
Problem:
After the car has warmed up, when it is idling for any duration (stop light), the car will idle funny, the car will sporadically shake and can be felt from inside the car. Also, when releasing the gas at a high RPM in a lower gear it will buck once. With the hood open, you can visually watch the engine shake every minute or two instead of appearing to be smooth motion.
Problem started with the VF Engineering CAI installed after I noticed that the oil filler cap was missing. 
Installed the factory stock air intake and replaced oil filler cap to see if problem goes away. Problem is still occurring. Is this something simple like a vacuum leak? Because I have checked, double checked, and triple checked everything related to the intake. I don't have a VAG-Com, so I can't scan it, but there is no CEL at the moment.


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## rustlerdude (Aug 13, 2007)

With the engine running, remove the oil cap. IS there any excessive pressure or vacuum on it?


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## Jkhami (Aug 31, 2007)

*Re: Rough/Shaky Idle (TimboAA)*

My friend's Golf had this problem before and I think he got new plugs and solved the problem.


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## NaKoRuRu (Jun 5, 2005)

check the oil level...


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## TimboAA (Sep 12, 2001)

*Re: (rustlerdude)*


_Quote, originally posted by *rustlerdude* »_With the engine running, remove the oil cap. IS there any excessive pressure or vacuum on it?

I wouldn't know what is excessive, but there is a vacuum on it. When the cap comes off the car starts to bog down and looks like its choking.
The oil level in the car is fine.
Spark plugs.....with not even 18k miles?


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## BlackRabbit2point5 (Sep 6, 2007)

*Re: (TimboAA)*

any time I mentioned this issue around techs when I worked for a dealer they just said its normal operation for a weird engine


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## TimboAA (Sep 12, 2001)

*Re: (BlackRabbit2point5)*

Haha...how is that "normal?"

It didn't used to do it....and when it was doing it with the CAI on....it was more severe.


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## Jkhami (Aug 31, 2007)

*Re: (TimboAA)*

This would be annoying to me too. I would also like to know what could be the issue? Anyone have an idea?


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## mikeygti18t (May 2, 2006)

*Re: (TimboAA)*

i work for a vw dealership and noticed that the idle on the 2.5 is not very smooth. I spoke with a qtm representative regarding the issue as a customer had come in complaining that his engine was "hunting" which in fact was just a rough idle , almost a "miss" with no apparent rythym. He did in fact advise that this was a normal condition and that another dealer had gone as far as replacing the whole engine after replacing plugs, injectors, coils, sensors etc. in search of a fix for this apparent idle problem. it did not resolve it......
so if in fact there is a problem, such as a vacuum leak from a poor seal on the oil cap, or a bad charcoal canister etc etc this would more than likely result in a fault code being stored...i.e system too lean or evap leak code.. perhaps a flash may become available later on that will make some adjustments to ecm program to smooth idle who knows....


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## silverA4quattro (Jun 22, 2004)

*Re: (mikeygti18t)*


_Quote, originally posted by *mikeygti18t* »_i work for a vw dealership and noticed that the idle on the 2.5 is not very smooth. I spoke with a qtm representative regarding the issue as a customer had come in complaining that his engine was "hunting" which in fact was just a rough idle , almost a "miss" with no apparent rythym. He did in fact advise that this was a normal condition and that another dealer had gone as far as replacing the whole engine after replacing plugs, injectors, coils, sensors etc. in search of a fix for this apparent idle problem. it did not resolve it......
so if in fact there is a problem, such as a vacuum leak from a poor seal on the oil cap, or a bad charcoal canister etc etc this would more than likely result in a fault code being stored...i.e system too lean or evap leak code.. perhaps a flash may become available later on that will make some adjustments to ecm program to smooth idle who knows....

An update would be nice. I had a problem at 3500 miles where I started the car and it was stumbling really hard, then I got a flashing CEL. I shut down the car and waited a minute. Then I restarted it and the same thing happened, with a solid CEL. I had it towed to the dealer.
When I got it back, they said there were a bunch of misfire codes and they cleared them and changed the oil. That's it. It never happened again, but I've always though the throttle response is horrible and the engine idles rough. Not really much I can do I guess.


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## TimboAA (Sep 12, 2001)

*Re: (silverA4quattro)*

I haven't put more than 50 miles on the car since I took out the CAI and put the stock one back in. I'll be driving it some distance and having to stop at tolls. We'll see how it acts then.


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## JETTSET (Oct 16, 2001)

*Re: (TimboAA)*

My car does the same thing. I am afraid it is the nature of the beast.


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## GodOSoot (Nov 1, 2004)

While were on the discussion of this WTF is up with the vacuum on the crankcase?
Any other car I have always had blowby coming out of the oil fill.
Emissions?


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