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  #1  
Old 08-03-2008, 09:22 PM
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Default help with vacuum leak?

So I'm 95% positive that I have a vac. leak. My car can barely idle, and it often sputters and wants to die when it is idling correct. My vac guage is now reading 12 in/hg at idle, and then goes to the normal 22 in/hg when I get up to speed. CEL just came on today, and the car is in limp, only boosting 1psi with a GIAC chip. MAF is fine, just cleaned it last week, car ran great. New plugs and coils put in two weeks ago. I pulled the N75, and there's oil dripping out of it when I removed it. I'm going to pull out all the injectors and take a peek as soon as it stops raining out, but my money is on vac leak....

where should I look for the most problematic vacuum hoses? Any diagrams to help me?
thanks
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  #2  
Old 08-03-2008, 09:36 PM
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You have a CEL. It's probably smarter to get the fault code(s) from the ECU before getting your hands dirty.
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  #3  
Old 08-03-2008, 10:51 PM
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Rubber vac line cost less than $0.50/ft, so buy 10ft and replace it ALL. The stock (Audi) braided vac lines dry rot too quickly and always start to leak.
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Old 08-03-2008, 11:15 PM
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Quote:
Originally Posted by onepoint8tee View Post
You have a CEL. It's probably smarter to get the fault code(s) from the ECU before getting your hands dirty.
I already did.

bank 1/1 bank 1/2 running lean
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Old 08-04-2008, 12:04 AM
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fuzzduster-where should I look for the most problematic vacuum hoses?

Id start with the lines running off the n75, the main one that gave me trouble was the line running to the wastegate...
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  #6  
Old 08-04-2008, 12:27 AM
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Originally Posted by fuzz_duster View Post
where should I look for the most problematic vacuum hoses? Any diagrams to help me?
thanks
All of them!

I, too, recommend reading the DTCs to see what exactly the MIL is on for before chasing your tail, but here goes:

Most common is the breather hose setup. There is a "T" at the back of the valve cover that gets oiled up and collapses or splits. Follow it down and there is a plastic pipe (or metal if you have a late AWM) hose that attaches to a formed rubber hose that also collects oil and collapses or splits. I believe there is a check valve in one of those hoses that can also cause an interior vacuum leak. Follow the "T" the other way and you'll find a series of rubber elbows and connectors heading towards the airbox that can also cause issues.

Check the oil dipstick tube for cracks. Pull up on the dipstick. If the tube comes with it, replace the tube.

Additionally, there are about 16,000 feet of 1/4" vacuum lines that become dry and are only held together by the exterior webbing. Check all of them. Most common is the line to the FPR. It's short and towards the rear of the head. Additionally, there is a long line that runs from the DV to the intake manifold across the front of the engine. It tethers to the timing belt cover and often can collapse or chafe through.

Hope this helps.
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  #7  
Old 08-04-2008, 11:38 PM
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Originally Posted by Tweaked View Post
Most common is the line to the FPR. It's short and towards the rear of the head.
i also suggest checking this one out as it would easily explain your lean condition
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  #8  
Old 08-05-2008, 12:10 AM
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Quote:
My vac guage is now reading 12 in/hg at idle, and then goes to the normal 22 in/hg when I get up to speed.
when at idle there isnt as much vac suction from the engine so a small leak would make a difference here. when you get up to speed theres more suction power, enough to mask a small leak. my vac is around -25 idle -27 @3200 rpm. you probably have a (few) decent size leak(s)
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Old 08-05-2008, 12:23 AM
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Originally Posted by Tweaked View Post
All of them!

I, too, recommend reading the DTCs to see what exactly the MIL is on for before chasing your tail, but here goes:

Most common is the breather hose setup. There is a "T" at the back of the valve cover that gets oiled up and collapses or splits. Follow it down and there is a plastic pipe (or metal if you have a late AWM) hose that attaches to a formed rubber hose that also collects oil and collapses or splits. I believe there is a check valve in one of those hoses that can also cause an interior vacuum leak. Follow the "T" the other way and you'll find a series of rubber elbows and connectors heading towards the airbox that can also cause issues.

Check the oil dipstick tube for cracks. Pull up on the dipstick. If the tube comes with it, replace the tube.

Additionally, there are about 16,000 feet of 1/4" vacuum lines that become dry and are only held together by the exterior webbing. Check all of them. Most common is the line to the FPR. It's short and towards the rear of the head. Additionally, there is a long line that runs from the DV to the intake manifold across the front of the engine. It tethers to the timing belt cover and often can collapse or chafe through.

Hope this helps.
Good advice there. There's also the small lines at the front and back of the intake manifold, which are very easy to replace. And it's not 1/4", I know it's a much smaller I.D. than that. Just get about 8-10 feet and you'll have plenty.
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  #10  
Old 08-05-2008, 12:46 AM
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update-

so today I took the codes off the car after double checking all the common problems and took it out for a spin. Its running strong, and sounds like its boosting 16 or 17 psi (like it should be) but its only boosting 5, and drops to 3 around the 4.5 - 6k rpms range. Vacuum was still being weird. So I decided to get underneath the car to be able to get a better look at some of the hoses that drop under the engine.

I found that the thick hose running from the turbo, down, underneath the engine block (also connected to the DV valve), and to the SMIC on the other side, had the clamps off! The hose ends slip onto a metal tube that connects them under the engine, and the tube was dripping oil, and the hoses were almost all the way off. So I slid them back on and clamped them tight. So I'll see if the car will balance out the running rich problem tomorrow, and HOPEFULLY run like its supposed to.
Oh and I took off the fuel rail to look at the injectors, and the last injector towards the drivers seat, has a broken head. It has two long cracks running though it, and it can swivel around. When I pulled it out of its seat in the manifold, all this oil/gas bubbled out and started hissing. So I need to replace that too.
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  #11  
Old 08-05-2008, 09:56 AM
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Originally Posted by fuzz_duster View Post
update-

Its running strong, and sounds like its boosting 16 or 17 psi (like it should be) but its only boosting 5, and drops to 3 around the 4.5 - 6k rpms range.
Do you have a boost gauge? Your ear is not an accurate boost gauge

What were the codes?
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  #12  
Old 08-05-2008, 11:20 PM
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yep, I have a guage. It is in limp again today, only boosting 3 - 5psi.

got my oxygen sensor today, but didn;t put it in because I want to MAKE SURE its not something I can fix for free or cheap. I'd hate to install the $130 part then find out I just had a hose with a nick in it....

anyways, tonights update - Found a small leak where the MAF wire harness connects below the N75 on the TIP. Clamped it and its now good. Went to go start the car and hope it would run better -

it didn;t. Barely starts now, and when I rev the engine repeatedly, then let off the gas and let it idle, it sputters to an almost dead stop, but slowly pulls itself back up to 850 RPMS. So I popped the hood again, and reved the engine via the DBW/throttle cable, and noticed a little smoke coming from the bottom of the engine block. It smells like burning rubber. And my cone filter sounds like its choking. It bogs real hard when on the gas, and sucks for air, then gets up to speed finally. It even popped once at me (aka backfired...)


I'm so fed up with this guessing game that's costing me my whole afternoons....I just want my car to run normal!!!
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  #13  
Old 08-05-2008, 11:21 PM
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Quote:
Originally Posted by Tweaked View Post
Do you have a boost gauge? Your ear is not an accurate boost gauge

What were the codes?
oh and the codes today were

"Running Lean - Bank 1/S 1"
"Running Lean - Bank 1/ S 2"
and the Limp code - Intermittent
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Old 08-05-2008, 11:23 PM
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Call me stupid, but there's NOTHING else that will make your vacuum show up as leaking.............right? So if my car is idling at 12 in/hg I HAVE to have a vacuum leak. Thats the only answer. Correct?
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Old 08-06-2008, 09:01 AM
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Have you tried pressurizing the system with an air compressor (only like 10 psi max)? There are some posts on how to do it, and it's often unbelievable the boost leaks that you'll find in the process.
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Old 08-06-2008, 09:18 AM
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yeah, thats what I did last night. I only found one small leak on the TIP, and fixed it
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  #17  
Old 08-06-2008, 10:02 AM
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Quote:
Originally Posted by fuzz_duster View Post
yeah, thats what I did last night. I only found one small leak on the TIP, and fixed it
Oh, you already checked... I'm just guessing at this point then. Maybe that funky injector you discovered is causing your lean condition, and the ecu is going into limp mode?

Or maybe a plugged cat would cause problems? That would cause low idle vacuum, but not sure if that would cause a lean condition though.
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Old 08-06-2008, 06:45 PM
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ok, so hopefully this is my FINAL update.

So two days ago when I filled my tank up, I threw some fuel injector cleaner in there just for ***** and giggles (couldn't hurt...). Well this morning I cleared my CEL code, and on the way to work I was boosting 13 - 15 psi, but I was lurching and bogging all over the road. The car was misfiring anywhere after 3 psi.

Let it sit all day at work.

After work, left to the post office to go pick up a package, car was still running the same. Then when I left, I was driving down the road, and noticed I was almost going WOT from 5 MPH, and the car wasn't jerking!!! Looked at the guage and I was peaked at 16 PSI, and it held steady for a couple seconds, then slowly dropped down to 10. Hit 4th gear, same deal, peaked at 14 psi, then slowly dropped. My problem was magically fixed!!!! It was fine 3/4's of the way home, then when I took off from the last stoplight, I noticed I was only boosting 3 psi. LIMP AGAIN.

So I'm thinking my problem HAS HAS HAS HAS to be a fuel injector. The car now idles different too. It will barely start, the rpms will bounce around the 600 -900 area, then all of a sudden it will jump up to 1k RPMS, and my gauge will drop to normal 19 -20 in/hg vacuum. Then a couple minutes later it will cut out again and idle crappy, and the guage will read 12 in/hg.
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  #19  
Old 08-06-2008, 07:10 PM
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you might wanna look at some check valves those things suck if those things break your car sounds like it has a cam in it ans when you rev up it fine but at idle it sucks. if thats what it is dont go to a parts store go back to the dealer ship there are like $50.00 but it will fix the problem
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Old 08-03-2009, 03:45 PM
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I had a similar issue, when ever I got into the boost much at all it sputtered, misfired-etc.

Turned out to be a coil pack, replaced, ran fine afterward, just something to think about.

The odd thing was it ran fun, but when I added the APR chip it started doing it.
Old 08-03-2009, 03:45 PM
 
 
 
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