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Discussion Starter · #1 ·
Hi,I've got a rather annoying problem with my 2001 1.8T Jetta... It's having a hard time idling and sometimes stalls out while attempting to idle. The OBDII codes are P1126 and PO172. Other forums/posts have suggested this could be an issue with the engine coils, which I've replaced with brand new ones last weekend. I just finished replacing the upstream O2 sensor and it still has the same behavior.
Another interesting symptom is back last fall the car's check engine light would flash while driving and it would almost all ability to accelerate. However, this would go away after a few minutes of doing it and it also wouldn't occur everytime I started the car. The owners manual suggests this is a bad catalytic converter, but my intuition says if that was busted... it would always have the same behavior. Something else to add, this symptom completely stopped last October/November... which I believe is when they change the gas mixture to lower the freezing point.
Any suggestions??? This is driving me nuts! Could I really have a busted Catalytic converter? or maybe the fuel injectors are shot??

Thanks for anything advice you folks might have!
 

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Alrighty sir.... Flashing CEL means something is wrong with your ignition. Could be your spark plugs, your spark plug wires, or what happens 99% of the time is your coil packs die. When they start to go out and you don't change them, you start spitting unburned fuel into your exhaust, and therefore into your catalytic converter. So sure, its possible you screwed up your cat because you didnt listen to your CEL lol.

Fuel injectors are fine... It's most likely either your secondary o2 sensor, your primary o2 sensor (not sure which one you changed) or your catalytic converter.

First, tell me what those codes mean... My other laptop w/ all my VAG stuff died, so I cant look them up.

We'll go from there.
 

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Discussion Starter · #3 ·
Thanks for the reply...

P0172 your fuel trims are running to rich.
P1126 is long term fuel trim add air, system to lean


Let me know what you think!! I'm hoping its not the catalytic converter...
 

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Symptoms of a vacuum and/or boost leak.

First thing you should do. Get one of those propane torches... You probably have one lying around somewhere. Turn on the gas, but not the flame. Pour propane all over your vacuum hoses while the car is running. If you hear your car rev up a little bit, theres your leak.

Keep in mind you have to get the nozzle of the torch pretty darn close to the hoses. I'd say no furthur than 1''. Dont worry, this wont hurt your car one bit, unless you turn the flame on ofcourse lol

If you really dont have access to a butane torch for some reason, you can use carb cleaner as well... But it makes a mess, and doesnt work as well.

Personally I think its just a vacuum leak because it wants to die on idle... But you never know, you could have a boost leak as well. Do this test and come back with the results. Also, conciter buying a boost gauge. You can monitor your vacuum and boost to help diagnose a variety of problems. They're not just for show! lol

Good luck!
 

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Boost you seem to beat me to these. You got the right .02 everytime. [good post]
 

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lol im actually extremely drunk rugignt now seeing its 240 a.m. saturday night but thanks dude lol I appreciate it. I do my berst to help fellow dubbers!
 

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Discussion Starter · #7 · (Edited)
Alright folks,

After a delay in making attempts to fix this car I'm back at it...

The codes continue to be:

P0172 - System too rich

P1126 - Long Term Fuel Trim Add.Air.,Bank2 System too Lean
*This code doesn't always trip, its currently not on only PO172 is tripping*


I've done a few things in hopes of locating a vacuum leak. The first thing I tried, as recommended, was to use the propane torch(less) idea... which unfortunately didn't yield any results...

The second thing I did was to obtain a vacuum gauge and hook it up... The Chiltons repair guide said that a healthy vacuum system has about 17-22 in Hg. The picture here: (http://www2.snapfish.com/slideshow/.../otsc=SHR/otsi=SPIClink/COBRAND_NAME=snapfish) below shows what hose I hooked it up to. The vacuum was steady @ 21 in Hg, even though the car continued to 'surge' while trying to idle...

The second thing I did was to unplug the hose pictured here ( http://www2.snapfish.com/slideshow/.../otsc=SHR/otsi=SPIClink/COBRAND_NAME=snapfish). I was surprised to find a film/residue of what seemed to be gasoline (at least it smelled like it). Could this be some of the unburnt fuel thats causing my issue?

Is there somewhere else i need to look for a vacuum leak?

Thanks for any advice you folks might have!!
 

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lol im actually extremely drunk rugignt now seeing its 240 a.m. saturday night but thanks dude lol I appreciate it. I do my berst to help fellow dubbers!
LOL I just had to comment on this. That's ****n' badass.
 

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lol there may be more of those posts tonight...

But to answer the OP, 21 in/hg is perfect. I have 22, really doesn't matter as long as its 20 or above.

That tube that has the gasoline smell in it is normal for your situation... You've been running rich, so unburned gasoline in your cylinders escapes past the piston rings, and deposits in your oil down in the crank case.

I honestly have no idea if this would cause your surging problem... Try changing your oil and see if that helps. You should change it anyway, as gasoline is very acidic for your bearings and seals.

So... Try that and let is know how it goes. If thats not it, you may be looking at a bad O2 sensor, but you have no code for it so I doubt thats the problem.

Good luck man.


EDIT: Oh yeah and that wont fix your rich problem... Forgot to address the problem at hand lol. Hmm...... Try cleaning your MAF (Mass air flow) sensor. You don't need anything special for this. Know, though, that the drill bit to take these screws out is impossible to find, so just grab a pair of vice grips, clamp on, and twist em' out. Works great. Anywhoo... Take the MAF out being VERY careful not to touch the wires in the actual sensor. You'll know what I mean when you see it. Get a plastic bag, place the sensor in it, and fill it up with isopropyl (?) alcohol. Let it sit for a while.

You can do that, OR go to autozone and buy MAF cleaner... Its like $8 bucks and might actually work a bit better since your spraying fluid over the internals, physically removing dirt/oil.

I dont know if this is the problem... But its a place to start. Thats the sensor that monitors how much air your sucking in, at what temperature, etc. So if its reading wrong, you can run rich.
 

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Only?? You ONLY let the problem go for a year lol? You should be thankful you DONT have a clogged CAT. But who said anything about that?
 

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Discussion Starter · #12 ·
Thanks for the replies folks!


I cleaned the mass air flow sensor about 3 months ago because its code was tripped. Once I cleaned it with the stuff from Autozone, the code went away...

Even though the code isn't there, could it still be the source of my problem?

I just bought a PCV valve online.. I got the part in the other day but I can't find the damn thing on the car.. anyone know where it is?

I also changed the upstream O2 sensor about 2-3 weeks ago in hopes of fixing the problem...


Any chance I've got a bad fuel injector pressure regulator, or potentially bad fuel injectors?

Thanks!
 

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Hey man sorry I haven't been keeping up with this, I totally forgot (and I can imagine an idle like this is very annoying).

So when you did the vacuum test, you said the idle kept surging right? How much did the vacuum reading fluxuate?

Was the vac reading at 21 in/hg when the RPM's were higher than normal, or right where it should be at 750 RPMs?

How does the car drive otherwise??

This ones buggin me cause usually poor idle is caused by a vacuum leak, MAF, or 02 sensors... And if you did your upstream, thats the one that would affect the idle if anything.

I say definitly replace that PCV valve (and check the line it connects to for cracks!). PCV's can sometimes cause this issue if they're clogged. Should be on the front of the engine under the intake manifold. Kinda hard to get to... Definitly do this when the car is cold! lol

I'll be on tonight, so if you answer those questions I'll come back and think a little more.

As of now, the only thing I could think of is the IAC valve, but I just found out the other day that 1.8T's dont have idle air control valves.

Lemme rack my brain a bit and I'll get back to you asap!
 

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Actually after thinking about this for a few minutes, forget the questions for now and change that PCV valve ASAP. Clogged PCV can indicate fuel buildup in your oil, which would explain that as well as a slightly rich mixture (PCV recirculates crank case fumes back into the air intake to limit pollution.. But the engine also counts on those fumes to help lean out the AFR's or air to fuel ratios)
 

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Discussion Starter · #15 ·
Alright... this is excellent... thanks for getting back to me...

I've got the PCV Valve in hand, but can't for the life of me figure out where it is on the car...

Its a small little thing... an 1" to 1 1/2" long... two skinny section about 1/2" in diameter and the larger (black color) section about an 1" in diameter.. that sound about right?


Thanks!
 

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Discussion Starter · #16 ·
Also... when reading the vacuum.. it didn't fluctuate at all while the engine was revving... and i seemingly missed your earlier description of where the PCV valve is...


I'll go give it a shot and let you know...

Thanks!!!!
 

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http://images.google.com/imgres?imgurl=http://www.fallastarmedia.com/vortex/eurojet/large/pcv02.jpg&imgrefurl=http://forums.vwvortex.com/zerothread%3Fid%3D3747836&usg=__xNKrQNg8eX66Zzd97lXRMjejDJU=&h=864&w=1152&sz=395&hl=en&start=2&tbnid=OucbcDWuALcVjM:&tbnh=113&tbnw=150&prev=/images%3Fq%3D1.8T%2Bpcv%2Bvalve%26gbv%3D2%26hl%3Den


That should be all the info you need! And yeah that sounds right...

But like I said man the thing is in the worst possible place lol

Let me know if after reading that thread, you cant find it. I'll try to be more specific
 

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Vacuum should definitly fluxuate while the RPM's change.... hmm...
 

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Discussion Starter · #19 ·
having a hard time finding the lower pcv hose... in the link you sent me.. the second picture... where is it in relation to the 'Y" hose the comes up over the engine?
 
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