rough idle.

[chaberjunkgti]

since vwvortex is dead or no one knows the answer, i figured i'd come here.

I have a 2002 gti 1.8t 108 k miles ( i know its a vw, but they share many parts with the TT) forge tip,3"dp to 2.5 magnaflow catback,forge splitter dv, unitronic stage 1+.

awp engine code. stock ko3s.

would an exhaust leak cause rough idle? possible lean condition?

i'm notorious for snapping my dogbone mount bolt. this is the fourth time it snapped. I think my new issue is related to it.

last night the bolt snapped while driving home. i was 1/4 mile (roughly, but probably less than that). from home so i drove it home. I was unable to get the bolt out before sunset today and i don't have a garage to work on it in, so i called it a day...tommorow i will do further work.

anyway..the car is idling very roughly. vacuum fluctuates between 5-10 hg but when held at a constant rpm (ex. 2200) the vacuum reads at 19-20 hg. i didnt step on it on the drive home so i don't know if boost is normal.

however, while under the car today, i noticed my flexpipe is well...very flexible (3" dp to 2.5" magnaflow catback) i think it may have become damaged as the exhaust makes a very loud crackling/popping sound upon reving, leading me to believe its a possible exhaust leak.

i checked the vacuum lines from the dv to the mani (how i have mine set up) and the one for the fpr and they look to be fine. where else should i look for vacuum leaks (common places of leakage)?

also, does this sound like a vaccuum leak, exhaust leak, or something else. obv the broken mount caused the engine to shift. so i think its very likely that its an exhaust leak, but how would that affect vacuum?

also turbo makes a whining noise under vacuum only while in gear..probably the turbo exhaust housing..also when the mount is bolted where it should be, it does not do this.

footnotes:

-dogbone mount bolt snapped
-rough idle
-flex pipe seems to be broken

thanks in advance for any insight on what could be the problem.

[Seerlah]

Having an exhaust leak will cause you to run lean (depends on how large of a leak), but that should not affect your vacuum. Your vacuum issue would have to do with a vacuum leak, which will also contribute to your lean condition and why you are seeing 5-10 in/hg (which says you have a rather large leak). I would say your rough idle has to do with a non-stoichiometric A/F condition. Do a boost leak test to narrow down where your leak is, and replace your flex joint. I would start there. No expert, though.

[chaberjunkgti]

turns out it was a vacuum leak. the line in the below picture (circled) is the one that came loose. however, i still had full boost..is this normal? i always thought a vacuum leak would lead to a boost leak as well.

http://i3.photobucket.com/albums/y64/matus/nig.jpg

[Seerlah]

Vacuum vs boost leak?

[chaberjunkgti]

Vacuum vs boost leak?

yeah, wouldn't a vacuum leak not cause me to reach full boost? regardless its fixed now i was just wondering.

[Seerlah]

Is there a check valve on that line that was loose, going to wherever?

[chaberjunkgti]

not sure as it was dark once i finally got under the hood but there is some kind of valve there. I just wrapped some duct tape around it temporarily...its not exactly easy trying to fix a car at a college campus with the limited tools i have but it idles at 20 hg now as it should.

[Seerlah]

Nvmd, I see the check valve off the line coming off the side of the IM (the ones on my vehicle are white/black, so I overlooked yours). Then I see another one more up the line, near your firewall. I am assuming that line that was loose is coming from your block breather (pure assumption), which would have to deal with your crank case ventalation and would not affect your boost. But when in vacuum air was not meant to travel in that direction, due to the check valve. And I am assuming that is what was causing your vacuum to be way off.

And you are no the first, and damn sure won't be the last to ghetto rig a part on your vehicle. I have wrapped eleectrical tape around ripped hoses, used radiator hose for a substitute oil dip stick tube, and currently have my power steering cooler zip tied to the front end clip. They all get replaced with upgraded or OEM parts eventually, but you need to do what you need to do make your car operational.

[chaberjunkgti]

thanks for the help. i may just start coming here over vwvrotex for technical questions, people here seem to know what they're talking about. And i've had plenty of ghetto rigged fixes in the past...i guess its just part of owning a german car.

[Seerlah]

Mess around and you may end up jumping on the Audi train [drive].

Never the less, these forum boards are meant for helping and educating. I didn't know jack about these cars when I first joined and purchased my vehicles. People on this forum board showed me the ropes and I basically just keep on trying to learn more and more. Glad I could have helped [cool].

[chaberjunkgti]

i will most definitely be jumping on the audi train once i finish school and make some real money.