Help me with my PCV valve please! 2004 1.8T

[Andrewiffic]

I have been searching and researching for the past couple days all about this. I think I have finally come to an understanding, but I would like some clarity if someone has experience with this. I have a 2004 1.8T and from what I've found it has a slightly different PCV valve design from earlier (prior to 2003) A4s. After much searching, here is a picture of what the pcv valve on my car looks like:



The issue I've been having is a rough idle and a CEL(MIL) coming on for misfires. Specifically this:

4 Faults Found:
17705 - Pressure Drop between Turbo and Throttle Valve (check D.V.!)
P1297 - 001 -
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 008 - - MIL ON
16685 - Cylinder 1
P0301 - 008 - Misfire Detected - MIL ON
16687 - Cylinder 3
P0303 - 008 - Misfire Detected - MIL ON


I have changed my DV already a few months ago and it seemed to help for a while, but now maybe because of the cold weather or something the misfiring is coming back. My research leads me to believe I have a vacuum leak and/or a bad PCV valve.

My question is, should I just replace the PCV valve or should I replace the connecting hoses to it as well as I've heard they can be crumbly? And if so does anyone know which ones go on a 2004 1.8T? And should I replace any of the 1-way check valves too or is there some way of testing them?
Thanks in advance.

Here are some photos of my engine if it helps:



I think the PCV is down here:


Not sure what this t-fitting is....it doesn't look like any breather valves I've seen online.






What is this capped off hose that leads to no where?


Different view from above

[old guy]

Yes that is the correct PCV valve for a 2004 1.8T. If you replace the PCV you should consider replacing all the hoses connected to it at the same time. They will probably self-destruct when you remove them. The capped off hose is normal.

The “T” connection is simply a “T” connection. The left hose is the vacuum source. The right hose connects to the N80 Evap purge valve located above the intake box. The lower hose connects to the LDP (Leak Detection Pump) located underneath the driver’s side rear wheel well liner.

Your next step should be to perform a boost leak test. The 17705 is more likely coming from a leak somewhere in the boost track between the turbo outlet and throttle body.

[Andrewiffic]

Awesome, thanks for the reply old guy! You're some sort of PCV guru because a lot of the best information I found in my searching was from your posts. I couldn't find any info on the t-connection so thanks for clarifying.

Also, I have ordered a new PRV, since I've heard that they can break after your PCV valve breaks and cause the 17705 fault too. Do you think that's a likely culprit?
This item:


I should also make a boost leak tester and test. Do I have to close off any connections to boost leak test or can I just pressurize the whole system?

[old guy]

The PRV usually isn’t involved with any sort of pressure drops. The PRV regulates the flow of air into and out of the block. It doesn’t check boost pressure.

When you do a boost leak test you need to disconnect the hose from the TIP to the PRV and plug it at the TIP. Also leave your oil filler cap off. This will prevent you from pressurizing your block through the PRV or through a defective check valve.

You can test your check valves by disconnect the vacuum lines connected to the intake manifold one at a time and using an air nozzle to apply pressure to the line. You should not be able to flow any air through any of the vacuum lines. If you can that would be an indication that the check valve has failed. This type of leak may not show up during the boost leak test since the leak is internal rather than external.

[Andrewiffic]

Great info thanks. I will update as I get into this.

[Charles.waite]

Consider getting an 034 PCV replacement set. The price is FAR better than the OEM parts and they should be just as durable.

[Andrewiffic]

Consider getting an 034 PCV replacement set. The price is FAR better than the OEM parts and they should be just as durable.

I looked at it, but it will actually cost more than double for the 034 kit than if I go with non-OEM PCV valve components from auotpartsway.

[MetalMan]

Consider getting an 034 PCV replacement set. The price is FAR better than the OEM parts and they should be just as durable.

034 doesn't make a PCV set directly compatible with the 2004's PCV system. Switching to 034 parts would require converting other PCV components to the ~2003 PCV system. IMO it's not worth it as I believe the 2004 PCV system is superior to pre-2004.

On my 2004 I refreshed the PCV system about 4 months ago. Replaced the PCV valve (as pictured in first post) with this one:
http://www.autohausaz.com/search/pro...archbutton.y=0
New crankcase breather O-ring:
http://www.autohausaz.com/search/pro...archbutton.y=0
And new breather hose elbow:
https://www.ecstuning.com/Audi-B6_A4....8T/ES2602472/
I was able to re-use the "crankcase ventilation tube":
https://www.ecstuning.com/Audi-B6_A4...PCV/ES2712562/
Also re-used the breather hose 3-way connector (attaches at valve cover):
https://www.ecstuning.com/Audi-B6_A4.../PCV/ES261027/
Cleaned out the pipes going to/from PRV, as well as the PRV (and reused that).

[Andrewiffic]

034 doesn't make a PCV set directly compatible with the 2004's PCV system. Switching to 034 parts would require converting other PCV components to the ~2003 PCV system. IMO it's not worth it as I believe the 2004 PCV system is superior to pre-2004.

On my 2004 I refreshed the PCV system about 4 months ago. Replaced the PCV valve (as pictured in first post) with this one:
http://www.autohausaz.com/search/pro...archbutton.y=0
New crankcase breather O-ring:
http://www.autohausaz.com/search/pro...archbutton.y=0
And new breather hose elbow:
https://www.ecstuning.com/Audi-B6_A4....8T/ES2602472/
I was able to re-use the "crankcase ventilation tube":
https://www.ecstuning.com/Audi-B6_A4...PCV/ES2712562/
Also re-used the breather hose 3-way connector (attaches at valve cover):
https://www.ecstuning.com/Audi-B6_A4.../PCV/ES261027/
Cleaned out the pipes going to/from PRV, as well as the PRV (and reused that).

Thanks! Appreciate it. I wish I had found this info 2 days ago, would have saved me hours of searching for PCV parts that only fit pre-2004 A4s. I have ordered the same parts that you did (but from autopartsway since they are located in Canada) and hopefully I can reuse my crankcase ventilation tube too. We'll see.

Did you replace your PCV because you were having issues? And if so what kind of issues or CELs?

[MetalMan]

Thanks! Appreciate it. I wish I had found this info 2 days ago, would have saved me hours of searching for PCV parts that only fit pre-2004 A4s. I have ordered the same parts that you did (but from autopartsway since they are located in Canada) and hopefully I can reuse my crankcase ventilation tube too. We'll see.

Did you replace your PCV because you were having issues? And if so what kind of issues or CELs?

The 2004 PCV system is quite the beast! My 2001 A4's PCV system is simpler (kinda similar to 2002-2003 PCV system). But since I became intimately familiar with 2004/2001 I realized how much better the theory is behind the 2004.

I refreshed it because I was doing a bunch of "while you're in there" type maintenance since I bought the car a couple months prior. No specific issues with it otherwise.

[Charles.waite]

034 doesn't make a PCV set directly compatible with the 2004's PCV system. Switching to 034 parts would require converting other PCV components to the ~2003 PCV system. IMO it's not worth it as I believe the 2004 PCV system is superior to pre-2004.

What are you talking about? https://store.034motorsport.com/brea...-silicone.html

I ran that setup on my 2004 for years without any issues. Yes, you lose the auxiliary breather tube (macaroni tube) but realistically that tube shouldn't be necessary, and I never experienced any issues with my PCV for 4 years with the setup. Looks like the price has gone up in the intervening years for the 034 kit, but if I were to do it again I woulds till buy 034.

However, holy crap those parts have gotten cheap. I know when I was fixing all my PCV stuff back in 2011, a full OEM refresh was hundreds of dollars. Crazy how cheap the parts have gotten. If thats the case, and you want to stay OEM, then for sure get those parts listed. Those are great prices!

[MetalMan]

What are you talking about? https://store.034motorsport.com/brea...-silicone.html

I ran that setup on my 2004 for years without any issues. Yes, you lose the auxiliary breather tube (macaroni tube) but realistically that tube shouldn't be necessary, and I never experienced any issues with my PCV for 4 years with the setup. Looks like the price has gone up in the intervening years for the 034 kit, but if I were to do it again I woulds till buy 034.

Yes I came across that, but that just proves my point; it converts the PCV system to a pre-2004 configuration. Granted I did miss the part that it includes everything necessary to achieve that conversion...

Did you ever have issues with 034's silicone "sweating" when used for PCV components? I have 034's breather kit on my 2001 (purchased in 2013) and the silicone sweats a decent amount of vapor even after a fairly short period of time.
This is one of the reasons why I don't generally recommend 034's silicone PCV stuff... I've used other brands of silicone components on my PCV system which didn't sweat at all and held up just fine to PCV vapors.

[Charles.waite]

Yea it sweats a bit but I never found that problematic. It's not like it's spraying oil everywhere.

[relative4]

For a boost leak tester, these are great, cheap, and will save you a bit of time. The one I got from them has been extremely helpful.

http://turboboostleaktesters.com/a4/

[Andrewiffic]

Fitted the new PCV valve and all is well! Thanks for the help everyone. I'm glad I ordered a new breather hose elbow too because it broke as soon as I took it off. I was able to reuse the other pipes which was a nice relief.

[migokazino]

Yes that is the correct PCV valve for a 2004 1.8T. If you replace the PCV you should consider replacing all the hoses connected to it at the same time. They will probably self-destruct when you remove them. The capped off hose is normal.

The “T” connection is simply a “T” connection. The left hose is the vacuum source. The right hose connects to the N80 Evap purge valve located above the intake box. The lower hose connects to the LDP (Leak Detection Pump) located underneath the driver’s side rear wheel well liner.

Your next step should be to perform a boost leak test. The 17705 is more likely coming from a leak somewhere in the boost track between the turbo outlet and throttle body.

do you know what size fitting and what the t shape connector is called i have a 02 a4 b6 1.8t and my t shape connector broke last week

[old guy]

do you know what size fitting and what the t shape connector is called i have a 02 a4 b6 1.8t and my t shape connector broke last week

I replaced mine with a universal "T" fitting from Autozone. Clicky click®

Simply trim off the arms for the appropriate size vacuum hose.

[migokazino]

I replaced mine with a universal "T" fitting from Autozone. Clicky click®

Simply trim off the arms for the appropriate size vacuum hose.

bet precciate it

[silverbear]

After much research and nearly buying the 034 kit, it seemed clear to me that, for my 2005 1.8t, it would be best to replace the stock system (as much as I hate all the clutter). I did that and working well again (no more burning oil smell).