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Discussion Starter · #1 ·
'99 B5 1.8T. The car just starting idling rough and idles around 900-950rpm. I ran a diagnostic with my VAG-COM (VCDS) and it only returns a single P1136 code (system too lean). Nothing that points to a single bank. I haven't had a chance to pop the hood yet but I thought I'd check to see if there's anywhere specific to start looking. I did a search for the P1136 code, but it seems to turn up threads with multiple codes in addition to the P1136 so I'm not sure if they apply to my situation.

The car otherwise runs fine. No problems accelerating on the highway. Just idles rough.
 

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I haven't had a chance to pop the hood yet but I thought I'd check to see if there's anywhere specific to start looking.

My guess is the issue is under the hood, so go ahead and pop away..
 

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Discussion Starter · #4 ·
My guess is the issue is under the hood, so go ahead and pop away..
LOL. That's where I suspect the problem is located as well. My hood support blew a seal the other day and I wasn't too keen on holding the hood up with a stick. The replacement strut just arrived today so I put in in when I got home from work. I started up the car to see if I could hear it sucking in any air other than where it's supposed to, but I couldn't tell just from listening so I'll have to dig around a bit more over the weekend. I had replaced the small vacuum lines with silicon hoses many years ago and they seem to still be intact so I'm hoping that will eliminate one of the potential problem areas.
 

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Connect the VCDS and check fuel trim while idling, partial/low load and full load. If you have a vacuum leak (you probably do) the fuel trim at idle and light load (high vacuum) will be lean, and when turbo pumps in, the mix will become rich.
Check the L hose above and check also PCV valve. Squeeze the hose going to the PCV valve and see if the idle stabilizes. You can confirm with VCDS fuel trim field if you are on the right track.
 

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Don't forget the well-named F hose, as well.

On my 2001 AUG 1.8T I have had to replace the L hose, the F hose/connector, and three of the four 3.5mm vacuum hoses. (I replaced the 4th as preventive maintenance.) Also have a look at the little one-way plastic check valves, which often crack and leak air.

I would also clean the MAFS and the throttle body. As mentioned above, VCDS is your friend here.
 

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Discussion Starter · #9 ·
I believe I found the culprit. The breather hose (058 103 213) just below the intake manifold was busted wide open as shown in the photo. It looks like the easiest way to get to it is to remove the intake manifold. There's just not enough room to get it free from the Tee connector. It's hard plastic and it mostly busted apart in pieces while I was trying to remove it. Luckily, the main section with the part number came off as one large piece. I noticed some oil sludge on the hoses that I hadn't spotted before so maybe this will also fix the oil consumption issue I've been seeing. ECS Tuning has a kit that replaces the hose and Tee fitting so I ordered one along with a new intake manifold gasket. Looks like I'll be busy next weekend.

IMG_20150529_101023_488.jpg
 

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Yep; that would definitely cause a CEL! You might as well do the PCV itself and the dog-leg while you are in there if you haven't replaced those yet. And don't forget new injector o-rings since the rail has to come out to pull the manifold. (You can get those at any auto parts store if you didn't put them in your ECS order.)
 

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Discussion Starter · #11 ·
Finally got around to fixing this yesterday. I pulled the intake manifold as outlined in this thread:

http://www.passatworld.com/forums/b5-information-base/158954-diy-intake-manifold-gasket.html

I found a couple of things in this thread that were unnecessary and created more problems during the assembly, which I'll discuss in a minute.

When I took off the manifold I failed to notice the vacuum hose connected to the underside of the throttle body. The hose was connected to a Tee fitting that broke apart when I pulled out the manifold. I spent more time getting the plastic out of the hoses than anything else. It was old and brittle and just shattered when I tried to grip it to get it out of the hose. I had to crush the hose with a pair of pliers to break the plastic into little pieces and then pick them out of the hose. I eventually got them all out and replaced the Tee fitting.

During the installation I found out that trying to reinstall the clips for the injectors and the electrical connectors was all but impossible with everything installed. The DIY thread has you remove these items in step 8. I found that all I had to do was remove the two hex socket bolts holding the fuel rail and then gently, but firmly, pull the rail up. The injectors and wiring harness all came out quite easily as a complete assembly. Installation was a snap as all I had to do was reseat the injectors and reinstall the two bolts. I haven't replaced the injector O-rings, but it should be a simple task. I just forgot to order them with the rest of the parts. I'm not smelling any fuel and there aren't any signs of leaking so it may not be necessary.

Curiously, my engine looks nothing like the photo in post #5 above. Mine is an AEB and I don't recall seeing the infamous "L" hose everyone talks about.
 

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Curiously, my engine looks nothing like the photo in post #5 above. Mine is an AEB and I don't recall seeing the infamous "L" hose everyone talks about.
The engine is post #5 is a 2001.5 AWM, drive-by-wire (mine). The AEB is drive-by-cable, so I would expect some differences, but I didn't realize the infamous L-hose was not present!
 
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