09 GLI: check engine light with no code and revs hang.

[dudeman08]

i took my car to the dealer friday and got a new tire and battery under warranty and when i left and got on the highway, i noticed that whenever i came to a complete stop, the revs would hang around 1000 rpms and climb slowly to about 1500 rpms and drop off every 2 seconds about 200 rpms. when it did drop down, it felt like a misfire or like it was cutting a cylinder for a split second. you could feel it through the car and more so through the pedals. ive got check engine lights constantly popping up but everytime i scan it, theres no code. i keep clearing it and after about 20 minutes of driving it pops back up. i have since stopped clearing the light and am just checking it periodically. any help would be greatly appreciated. its really annoying.

[TT-Tom]

Is the car stock? If not list mods please, also what are you using to scan the car for codes?

[dudeman08]

car has:
BSH: atage 1 and 2 true seal intake, throttle body pipe, billet pendulumn mount
AWE: turbo discharge pipe
Forge: dv spacer
42DD: 3" cat-less downpipe
Revo: stage 1 tune

im using the ECS Tuning v-checker scanner to scan the car. its vw/audi specific. ive used this many times for many things and it can do an awful lot and i was quite suprised at what it can do. heres a link to it on their site:

http://www.ecstuning.com/Volkswagen-.../Tools/ES9950/

[dudeman08]

bump. im thinking about doing the throttle body alignment procedure for $#&%$ and giggles.

[dudeman08]

bump. anyone?

[Slayer]

If the revs are bouncing around, it could be a vacuum leak

[dudeman08]

my boost gauge is showing the vaccum and boost where it should be at. i thought that too, but i doubt it. i cleared the light today and got 3 miles before it popped back on again.

[dudeman08]

should i take a video and post it on here to show whats going on?

[ViRtUaLheretic]

Id say find a local with vag-com and have them scan your car.

[dudeman08]

today when i was seafoaming my engine and cleaning my maf sensor, i noticed that my boost gauge tubing had been crushed and possibly split under the battery hold down. who ever the tech is that put the battery in is an idiot, and theres nothing i can do as far as complaining to the dealer because "it shouldn't have been there in the first place". that isnt what they said, but what they will say if i did complain. i removed my new south performance pcv boost tap and put the factory piece back in and cleared the computer and it ran fine for a little bit, untill i parked the car for a half hour and came back out and started drving again. it started acting up again slightly, but not all the time like it was. the good thing is the check engine light didnt come back on and ive driven the car 20 miles so far, as compared to the driving 5 miles and having the cel pop up, since i cleared the computer and re-installed the stock piece. is it possible that the reason its still happening is because the computer could still just be re-learning since i cleared it?

[dudeman08]

so, it turns out that the crushed and split boost gauge tubing on my mk5 was only part of my issue. my check engine light came back on after i installed the stock pcv tube and went for another long drive and still had no code. i decided to poke around the engine bay for a minute and accidentaly bumped the intake pipe that goes from the maf to the inlet of the turbo and it moved. i grabed it and shook it and noticed that the clamp that secured the silicone conector to the inlet of the turbo has broken off and the pipe is just sitting over the turbo with the inlet wide open, which would explain the increase in "spool" noise. so to recap, it was a tiny vacuum leak from the boost gauge tubing, and the big thing was the turbo being wide open, which resulted in the engine trying to guess how much air was going into the engine and trying to estimate how much fuel was needed, which would explain the misfiring at a dead stop watching the revs rise and fall because the maf wasnt giving a reading. all this crap from a damn clamp.

[Slayer]

I called that one right on the money!

[TT-Tom]

I've seen this same issue when we were developing the BSH intake, we had many different issues with the direction of flow and this "rev hang" the production models are obviously correct but these cars have extremely sensitive mafs and a leak or flow problem before or after can cause issues with rev hang. Glad to hear your back in action!