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Rough Idle - Start up & Warm

glory

Ready to race!
For a few weeks now I have been having the problem of my car idling rough (I can feel it shaking through the seat) during cold starts and even when its warm and sitting at a light. I thought maybe it was a bad tank of gas, so I nearly drained her (had 80kms left) and filled her up again with 91 (highest we have in town). Issue is still there though.

What happens is when it's cold it really shakes and once the revs drop and idles normally it still shakes but not as bad. In traffic, idling it shakes enough to notice it. Sat in my mom's car (2012 GTI) and hers idles nicely (same gas station I use) from cold start to normal idling. Even my fathers 2011 Golf 2.5L idles more smoothly then mine.

I tried logging some info on it, and only thing noticeable was the knock sensor voltage on cylinder #1 was higher then the others (0.9V vs. 0.6V) and right off the bat it counted 4 misfires in cylinder #1. But I am unsure if the misfire counts are actual misfires or just from the car starting. After a minute or so the misfire counts went away. Any idea what I should be logging? Or should I just take it to my dealer and have them look at it?

Thanks in advance for the advice!
 

Bino

Go Kart Champion
Looks like you gonna need a new intake. While there do that take a look at your valves. It's covered untill 60k miles.
 

glory

Ready to race!
New intake? Carbon scrub? Wow was not expecting that. Can is stock engine wise, and has 16000 kms on it (9900 miles). Guess I should take it in under warranty eh?

Sent from the White north with magic
 

Bino

Go Kart Champion
New intake? Carbon scrub? Wow was not expecting that. Can is stock engine wise, and has 16000 kms on it (9900 miles). Guess I should take it in under warranty eh?

Sent from the White north with magic

Well no carbon build up then. But sounds like you have a stuck intake runner. Common in these cars. Stock or not.
 

kennega

Ready to race!
It's under warranty so I'd definitely take it in.

Another test if you're seeing misfires, I'd take cyl 1 coilpack and swap with cyl 2. If the issue follows to cyl 2, it's the coil. If not, swap plugs between the cylinders and again, see if it follows.
 

Bino

Go Kart Champion
Well I have new plugs and R8 coils when I had my intake replaced. I had misfires on cyl 1 and 3. After they replaced my intake and did a complete carbon cleanning. All misfires were gone.
 

Talguy

Go Kart Champion
Yea definitely change out your spark plugs and coil packs first before you do anything else. I've had pretty bad misfires on two occassions and they were solved by new spark plugs and coil packs
 

TXBDan

Go Kart Champion
Holy jump to conclusions mat you people.

There are tons of things that can cause a car to idle rough. Get a VAGCOM and scan it before you go throwing random parts at it.
 

glory

Ready to race!
Took the car in today and they said the problem is the fuel pressure regulator. They have to order one in and can't get me in until Friday.

Question, I am going on a 1300km round trip on Friday, should I not use my car or am I fine?

Sent from the White north with magic
 

maxtdi

Go Kart Champion
Took the car in today and they said the problem is the fuel pressure regulator. They have to order one in and can't get me in until Friday.

Question, I am going on a 1300km round trip on Friday, should I not use my car or am I fine?

Sent from the White north with magic

I wouldn't use the car.
 

glory

Ready to race!
Ya, it's staying at home and taking a different car. Hopefully this fixes it.

Sent from the White north with magic
 

glory

Ready to race!
Took the car into the dealer today and this is what they fixed:

-Replaced Injectors and seals (not fuel pressure regulator as I was told on the phone before)
-Replaced intake manifold position sensor

Haven't taken it on a long drive or a cold start yet, but hopefully this is all it was.

In the cause part of the write up this is what they put:
Faulty Injectors. Vehicle is running rough. Random misfires in value block 15. Code P2015 had come up for intake manifold runner position sensor. Intake was keeping vacuum.
 

glory

Ready to race!
So been a few days since the car was at the dealer. Didn't know if I was being too anal about it or just over thinking when I got it back, but there was a bit of shudder when idling. So thought a fresh tank of gas would help, well that wasn't helpful.

Still rough idle during cold start up and a slightly less rough idle during idling at operating temp. It is better then before, but I can still feel it. Found out today if idling in neutral and put the clutch in, the roughness becomes greater. Any idea what this could be? I'll be keeping an eye on it over the long weekend and give VW a call after.
 

dcarony

Ready to race!
So been a few days since the car was at the dealer. Didn't know if I was being too anal about it or just over thinking when I got it back, but there was a bit of shudder when idling. So thought a fresh tank of gas would help, well that wasn't helpful.

Still rough idle during cold start up and a slightly less rough idle during idling at operating temp. It is better then before, but I can still feel it. Found out today if idling in neutral and put the clutch in, the roughness becomes greater. Any idea what this could be? I'll be keeping an eye on it over the long weekend and give VW a call after.

Results?
 
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