2004 Audi A4 1.8T, Lean and High Idle errors

[Redfish1]

Need help. I have a 2004 A4 1.T Quattro. I have replaced breather hose, crankcase hose, and PVC. Cleaned MAF. Also, replaced valve cover gasket and spark plug ring gaskets (this was purchased as a set) due to oil leaking into spark plugs. I'm still throwing P0171 (system lean) and P0507 (idle higher than expected). When I pull the dipstick I get a strong sucking sound and the engine almost dies, but never actually does...just runs really rough and acts as if it will die. I tried pulling off the oil cap and I can't because of the strong suction created. What is causing this strong suction? I can't find any leaks, as I have gone thru the vacuum system and replaced cracks. The engine at start-up runs at 800 rpms...then after couple minutes jumps up to 1200. I have replaced spark plugs and they are gapped at .32 (everything is stock in this engine). I did replace the coils, but that did not help. I didn't expect new coils to help...just a gut feeling. When I drive the car it runs fine at high rpms. Before I replaced all hoses and PVC I was getting terrible gas mileage. At least now it's back to normal with the gas mileage, but I'm still getting the jump in RPM's at idle after a normal 800 rpm start-up.

Why would removing the dipstick while engine running make a loud sucking sound and why is it impossible to remove oil cap while engine running? Is this normal or do I still have a vacuum leak which is causing this?

Any advise or similar issues out there? Help much appreciated.

If I unplug the MAF sensor the engine starts to run rougher.

One last note. There is a hose coming from the manifold to the crankcase bleeder assembly. When I pinch that hose the engine actually runs smooth. I hear a sucking sound coming from the PCV, but when I pinch the hose the sucking sound from the PCV stops and the engine runs smooth. Any one have any ideas? Like I said, impossible to remove oil cap and strong sucking sound from the dipstick when I remove, while engine running.

[spunkz]

try to clean the throttle body i had similar problems just remove the clamp then hose then get sum1 to sit in the car turn the key all the way but dont start car let that person press on the gas and spray the throttle body cleaner in there make sure the one you buy is safe for sensors and what not

[EBG 18T]

One last note. There is a hose coming from the manifold to the crankcase bleeder assembly. When I pinch that hose the engine actually runs smooth. I hear a sucking sound coming from the PCV, but when I pinch the hose the sucking sound from the PCV stops and the engine runs smooth. Any one have any ideas? Like I said, impossible to remove oil cap and strong sucking sound from the dipstick when I remove, while engine running.

Do you have a vagcom? what is your vaccumn reading at idle?

[Redfish1]

No, I do not have VAGCOM. Just an OBD-II scanner. I'm planning to make a trip to the parts store and get a compression reader. Will report back later.

[downhillracer]

I think when you replaced all your pcv/vacuum hoses you may have reversed a check valve maybe. Or perhaps a check valve is bad. Check the one right above the suction jet pump. That one seems to fail the most.

[Redfish1]

Well, I just took off the check valves and they all function correctly. I tested by blowing in one end and had air flow. Then I blew air threw the other end and nothing. Seems to work...if I'm correct how a check valve works. Is that a proper assessment? Also, I cleaned the TB and didn't notice a difference. It wasn't dirty inside the TB at all. I'm still getting a strong suction thru the dipstick. Also, when I pulled off the jet suction pump the top of it popped-off. Has an orange piece at bottom that connects to the top of the jet suction pump. I assume that is the pump itself. This was not off prior to removing check valves. Appears it just pops right back in, is that correct? I didn't see any cracks or tears on any hoses when I was removing and inspecting check valves. Lastly, I didn't touch any check valves during my installation of the crankcase breather has and crankcase breather valve. There are not any on that line. Only thing I can think is that bleeder assembly which attaches the crankcase bleeder hose to the breather hose is not functioning properly. I believe it has two check valves? Maybe that failed (bleeder assembly). I really do not want to remove that again. Was a PITA and risk breaking more stuff under there. Thoughts? Should I run a pressure check? Would that tell me if a check valve is bad or any leaks?

[old guy]

The suction jet pump is not supposed to separate. You need to replace it. If you just snap it back together it will blow apart again under boost. You can glue it together temporarily if you want. Be sure to look closely into the two sections. there is a ridge on one side that fits into a groove on the other side. If you don't align them it will not seal back properly. As to the vacuum when you remove your oil cap: It sounds like your PRV (pressure regulating valve) isn't working properly. When you are at idle the PCV valve underneath the intake manifold ventilates the block and fresh air enters through the PRV. Sounds like yours isn't letting air in. Here is a little more info to better explain the crankcase ventilation system.

[Redfish1]

Replaced PVC with new part from Audi dealership. Also, replaced the suction jet pump. Still have the strong sucking sound coming from the dipstick when I pull it. My next plan is to take a picture of the two hoses coming of the side of the manifold. One of the two hoses goes from the manifold to the crankcase. When I pinch that particular hose the engine seems to run fine and the PCV stops the strong sucking sound. As well, I can pull the dipstick without the strong sucking sound. Not sure what the purpose of that particular hose is, but I think it's causing some problems ? Any thoughts. I really appreciate everyones help to this point.

[Redfish1]

The "T" fitting for the crankcase breather system has two check valves built in..is that correct? Could that "T" fitting go bad? Seems odd. When I removed didn't notice any cracks in the "T" fitting. Man this is frustrating.

[old guy]

Take another look at my previous post and review how the crankcase ventilation system works, especially when off boost. I think the problem is with your PRV valve not your PCV valve. It sounds like your PCV valve is doing what it is supposed to do; Ventilate your block. However, you need an air inlet so you don't pull a vacuum on the block. That is where the PRV (pressure regulating valve) comes into play. The PRV is the round, flat topped valve on the back of your valve cover with a line running to the TIP.

[Redfish1]

My bad. I replaced the PRV (black puck, spaceship looking part) with a new part from Audi. I incorrectly said PVC. I don't think the 2004 Audi 1.8T has a PVC valve becuase of the updated "T" bleeder assembly. Anyway, yes I have a new PRV from the dealer and I installed. The PRV is making a loud sucking sound. Not sure is that a bad PRV or if a I have issues coming from the air intake?

[old guy]

If your PRV is operating correctly but you are still getting excessive vacuum in the block when off boost then you probably have a defective PCV or "bleeder" valve. It should provide a metered amount of vacuum purge to the block. It sounds like you are getting excessive vacuum. That's probably why you are getting the sucking noise from the PRV.

Edit: This is also probably causing your high idle and lean code issues. You are pulling excessive air through the crankcase breather.

[Redfish1]

Here's a link of the "T" bleeder valve (aka PVC valve) in my 1.8T. I had that part off couple days ago and it looked good. Although, it does appear it has two check valves, which I guess could go bad. Anyway to test that before I rip it out again? Could I blow air in that "T". Air should not go in that direction, correct. Any other ideas that would case the excessive suction in the engine before I take off the "T" Valve?

http://www.ecstuning.com/Search/Blee..._Valve/ES7940/

[old guy]

Here's a link of the "T" bleeder valve (aka PVC valve) in my 1.8T. I had that part off couple days ago and it looked good. Although, it does appear it has two check valves, which I guess could go bad. Anyway to test that before I rip it out again? Could I blow air in that "T". Air should not go in that direction, correct. Any other ideas that would case the excessive suction in the engine before I take off the "T" Valve?

http://www.ecstuning.com/Search/Blee..._Valve/ES7940/

Correct. You should not be able to blow air through the "T". You should be able to suck air through it. Did you have this problem before you replaced the PRV?

[Redfish1]

Yes. PRV was making a loud sucking sound. That's why I replaced. And now it still makes that same sound with a new PRV.

I think the "T" valve is good because I can't blow air through it. But, if I pinch the hose connected the the "T" valve (which is connected to the mani) the engine runs normal rpm's, no sucking sound from the PRV, and I can remove the dipstick without the excessive sucking. Everything seems to go normal when I pinch the hose from the mani to the "T" assembly. Strange or normal?

Update: The hose is coming from the top of the "T" to the mani. Should I take a photo of this hose or are you familiar?

[old guy]

Yes. PRV was making a loud sucking sound. That's why I replaced. And now it still makes that same sound with a new PRV.

I think the "T" valve is good because I can't blow air through it. But, if I pinch the hose connected the the "T" valve (which is connected to the mani) the engine runs normal rpm's, no sucking sound from the PRV, and I can remove the dipstick without the excessive sucking. Everything seems to go normal when I pinch the hose from the mani to the "T" assembly. Strange or normal?

Update: The hose is coming from the top of the "T" to the mani. Should I take a photo of this hose or are you familiar?

I am looking at the Bentley vacuum diagram for the '04+. It shows the "T" connecting to a crankcase breather, pretty much the same as the '03 but without the "T". When you removed the "T" did it connect to a breather coming out of the crankcase ventilation housing?
Clicky click

[Redfish1]

I don't recall seeing that part on the "T" when I removed the "T". Should I have that part? If yes, where does it go on the "T". Hopefully I answered your question.

[old guy]

I don't recall seeing that part on the "T" when I removed the "T". Should I have that part? If yes, where does it go on the "T". Hopefully I answered your question.

That part is what plugs into the ventilation housing just above the oil cooler.

Here's my thoughts on your issue. At idle the intake manifold provides the vacuum to ventilate the block. The air is drawn into the manifold through the breather tubes running from the manifold to the ventilation housing. The air is being drawn through the block via the PRV, which is in turn pulling air from the TIP. The air is being metered in two places. The PRV meters how much air goes into the block and the PCV meters how much air is being pulled out of the block into the intake manifold.

You stated that if you pinched off the vent tube the PRV quit making noise and you idle smoothed out. This sounds like you are getting too much vacuum pulled on your crankcase. So either the PRV isn't letting enough air in or the PCV is pulling too much out. If the problem is the PRV not letting enough in you would have a high vacuum on the crankcase bit it shouldn't affect the idle. If the problem is the PCV pulling too much out then you would be getting excessive air in the manifold (high idle/ leaned out) and also trying to pull more air through the PRV than designed (making a sucking noise). My guess is a defective PCV. I don't think the issue has anything to do with your check valves. If they weren't working properly they would restrict your vacuum pull, not accentuate it.

Hope my ramblings make sense.

[Redfish1]

Ok. I understand. But, there is not a PCV on the 2004 Audi A4 1.8T. Not that I recall. If there was I didn't see one. Is that the problem? I can't find a PCV part for the 2004 Audi 1.8T.

Would a bad MAF create that much excessive suction on the oil cap and dipstick. Don't intend to switch gears....just a side note. I wouldn't think a bad MAF would cause excessive suction in the engine?

[old guy]

Ok. I understand. But, there is not a PCV on the 2004 Audi A4 1.8T. Not that I recall. If there was I didn't see one. Is that the problem? I can't find a PCV part for the 2004 Audi 1.8T.

Would a bad MAF create that much excessive suction on the oil cap and dipstick. Don't intend to switch gears....just a side note. I wouldn't think a bad MAF would cause excessive suction in the engine?

The MAF shouldn't have anything to do with how much vacuum is being pulled on the crankcase. I did a little searching and I can't find an application of that PCV for an '04 either. Which leads us back to the "T" connector. Something has to regulate the amount of vacuum being pulled on the block which means the "T" is functioning as the PCV. Sounds like that is your problem.

[Redfish1]

I was afraid of that. Not a fun part to remove. I just installed entire new line from crankcase to PRV. Oh man. Wish I would of known to check that "T" valve before I reinstalled. I'll pull out and report back.

One more question before I sign off. Any ideas how I can check the "T" is bad or should I just purchase new one?

[old guy]

I was afraid of that. Not a fun part to remove. I just installed entire new line from crankcase to PRV. Oh man. Wish I would of known to check that "T" valve before I reinstalled. I'll pull out and report back.

One more question before I sign off. Any ideas how I can check the "T" is bad or should I just purchase new one?

It is performing two functions. It is a one way check valve (which you can easily check). But it also has to meter the amount of air (vacuum) that is being pulled on the block. Not sure how you would check that.

Good luck!!

[Redfish1]

Pulled the "T" assembly off today. Inside is a small disc, which I assume is the PCV valve. I think that regulates the airlfow? From what I could see the small disc inside the "T" tube was not functioning properly. It was stuck open and when I shook the "T" I could hear it rattling around in there. Stuck a screwdriver down there and the disc appeared it was broken off whatever it should attach to. I'll know more tomorrow when I go to parts store and purchase new one. Then I can do some comparing. I think I finally found my vacuum issue...I hope. Here's a link to the part I'm referring to. Will update more tomorrow after installing new part. My guess is that valve was stuck open allowing excessive amount of air to enter the block, making my PRV work overtime. We shall see tomorrow after install.

http://www.ecstuning.com/Audi-B6_A4-..._Valve/ES7940/

[diagnosticator]

The suction jet pump is not supposed to separate. You need to replace it. If you just snap it back together it will blow apart again under boost. You can glue it together temporarily if you want. Be sure to look closely into the two sections. there is a ridge on one side that fits into a groove on the other side. If you don't align them it will not seal back properly. As to the vacuum when you remove your oil cap: It sounds like your PRV (pressure regulating valve) isn't working properly. When you are at idle the PCV valve underneath the intake manifold ventilates the block and fresh air enters through the PRV. Sounds like yours isn't letting air in. Here is a little more info to better explain the crankcase ventilation system.

Outstanding reference! That will clear up a lot of confusion about the crankcase ventilation functions. Thanks for posting this!

[Spinshag]

I was afraid of that. Not a fun part to remove. I just installed entire new line from crankcase to PRV. Oh man. Wish I would of known to check that "T" valve before I reinstalled. I'll pull out and report back.

One more question before I sign off. Any ideas how I can check the "T" is bad or should I just purchase new one?

I'm having lean error codes and rough idling. It sounds like a diesel... (A4 B6, 1.8t)

I replaced a bad check valve and am ordering a EVAP purge valve this week... so I have ~$100 into a self fix... after this, I am heading to the garage.

If you get codes from a VAG-COM, or figure it out, let me know... I am still hoping this works.

Codes: 17519 - Oxygen (Lambda) Sensor Regulation: Bank 1: System too Lean

P1111 - 002 - Lower Limit Exceeded

17705 - Pressure Drop between Turbo and Throttle Valve (check D.V.!)

P1297 - 001 - Upper Limit Exceeded

16684 - Random/Multiple Cylinder Misfire Detected

P0300 - 008 - Implausible Signal

16685 - Cylinder 1 Misfire Detected

P0301 - 008 - Implausible Signal

16686 - Cylinder 2 Misfire Detected

P0302 - 008 - Implausible Signal

16687 - Cylinder 3 Misfire Detected

P0303 - 008 - Implausible Signal

16688 - Cylinder 4 Misfire Detected

P0304 - 008 - Implausible Signal

I cleared them, and only the first two show up again...

[Redfish1]

OK. Got her fixed! My final problem was a busted "T" (aka Crankcase Bleeder Valve Assembly). In the late version 2004 A4 1.8T the PCV valve is built-in to the updated "T" assembly. The small disc inside the "T" assembly was broken-off and air was flowing in both directions. My understanding is the PCV valve regulates the airflow, which my PCV valve was wide open. My oil cap and dipstick now come off with ease and NO sucking sound whatsoever.

Really appreciate old guy for all the help. Made the process less frustrating and confirmed my findings. Also, helped me sleep better knowing that had to be the problem.

I hope this is a good ref. for others experiencing vacuum issues. You never know where you'll find the problem. In my case the problem was hidden...you couldn't see any tears, cracks, etc. and appeared "T" was functioning properly until you disassembled and blew into both directions.

Thanks Again!

[Spinshag]

Where is the throttle body?

[Redfish1]

Where is Throttle Body?

On the '04 Audi A4 1.8T the TB is on the front right. So if you are looking at the engine from the front it's the part that comes of the mani and you will see a vent tube (about 3" diam) coming off of that.

If you need a pic let me know and I can download one for you. Not sure my description is good enough.

[Spinshag]

Got it. Thanks!

[Spinshag]

OK. Got her fixed! My final problem was a busted "T" (aka Crankcase Bleeder Valve Assembly). In the late version 2004 A4 1.8T the PCV valve is built-in to the updated "T" assembly. The small disc inside the "T" assembly was broken-off and air was flowing in both directions. My understanding is the PCV valve regulates the airflow, which my PCV valve was wide open. My oil cap and dipstick now come off with ease and NO sucking sound whatsoever.

Really appreciate old guy for all the help. Made the process less frustrating and confirmed my findings. Also, helped me sleep better knowing that had to be the problem.

I hope this is a good ref. for others experiencing vacuum issues. You never know where you'll find the problem. In my case the problem was hidden...you couldn't see any tears, cracks, etc. and appeared "T" was functioning properly until you disassembled and blew into both directions.

Thanks Again!

I caved and took it to the dealer... I had the same problem. Does this problem happen often?

[PDX04a4]

happened to me as well, had that replaced with a bunch of other broken tubes/hoses under the mani and got the car back to normal.

[dafowler88]

Can someone help me locate the PCV, "T", Valve on my car?
2005 Audi A4 1.8t

[bedlam]

Got exactly same problem. Been looking for PCV everywhere now realise it has modified T instead. Can someone please tell me where this T is located. Thanks

[dkrants]

I have the same problem with the vacuum in the engine. Can someone tell me where the T-valve (bleeder valve) is located?
I have B7 but it might be similar to B6.

Thanks a lot.

[Dewey W]

Hey Everyone. I know this post hasn't been looked at in a while but I was hoping someone could send me some directions on replacing the crank case bleeder valve. I purchased the part I needed and was hoping to do it myself but after locating it i'm not sure what the steps are to get everything else out of the way so I can replace it. Any help would be greatly appreciated.

[old guy]

Everything you will need to know to change out the cranckcase breather can be found here. Clicky click It's a lot of reading but worth it since you will be dealing with this stuff again in the future.

[jonesfunk]

I know this is an old thread, but it was a HUGE help to me recently. I created an account just to thank everyone on this thread and to add my experience with this problem.

Car: 2005 Audi A4 B6 1.8T Quattro Avant, 105,000 miles

Symptoms: Rough idling (especially after starting), decreased power, decreased fuel economy, check-engine light on (but not blinking). Identified and repaired a vacuum leak in the line running from the valve cover to the block, but this did not resolve the symptoms. After this initial repair, I then noticed a strong vacuum around the edges of the Pressure Regulating Valve (PRV), and the engine would almost kill when removing the dipstick.

Diagnosis: Using the information in this thread, I was able to narrow the problem to either the PRV or the Pressure Control Valve (PCV), but most likely the latter. I purchased both parts from my local dealer (approximately $130, total).

Repair: Not a ton of fun. Getting at the PCV involves draining the coolant, disconnecting the injectors and about 10 coolant and vacuum lines, and removing the throttle body and manifold. I removed the entire assembly indicated here with red lines (photo credit to rollaphillie):


Sure enough, the PCV was shot. By blowing air into each of the four attachment points, I found that air was flowing freely in any direction.

I also swapped-out the PRV while I was at it, and also put on new manifold and throttle body gaskets.

For clarity, here is a pic of my old parts, PCV on the top, PRV on the bottom:


Results: Back to (almost) normal. No more check-engine light, engine idles smoothly, and no more audible vacuum noises anywhere under the hood. Alleviating this issue exposed some hesitation under heavy acceleration. Swapping the spark plugs and refilling the tank with premium fuel (no thanks to the significant other going on auto-pilot whenever selecting fuel grades) fixed that issue as well.



Special thanks to Old Guy, who apparently knows everything.

[tactowntt253]

Why exactly did you need to flush the coolant?

[jonesfunk]

Why exactly did you need to flush the coolant?

Didn't say flush, I said drain. Or at least reduce some of the volume. Getting to those parts in the 1.8T requires removal of many coolant hoses. Unless you want coolant in your cylinders and vacuum lines, it's best to be careful.

[nuugen]

Didn't say flush, I said drain. Or at least reduce some of the volume. Getting to those parts in the 1.8T requires removal of many coolant hoses. Unless you want coolant in your cylinders and vacuum lines, it's best to be careful.

Hmmm. I am wondering why you need to remove all that stuff? We do those repairs weekly without removing anything, except unbolting the coolant reservoir and moving it over out of the way..