Needing help with P2187 Too Lean at Idle code

[Weixb]

Hello all!

I am struggling with finding a solution to P2187- System lean at idle.

Attached is a VCDS scan from about an hour ago.

This is my first time working on a car, so I’m still trying to learn some of the terminology; my advance apologies for poor descriptions, or if I’m not providing enough information!

The car has been running great; no noticeable decrease in performance except for perhaps reduced gas mileage. The P2187 code started popping up a few weeks ago, and after clearing the code several times, it has started popping up more frequently.

The only noticeable issue has been that the car will take slightly longer to turn over if it has been sitting for a while- maybe a second and a half, rather than almost instantaneously, as it does when it’s been recently shut off.

So far, I’ve noticed or checked the following:

Car idles fine; revs don’t increase or decrease at all at idle.

Slight hissing coming from the PCV valve area, but it’s relatively quiet. Engine idles fine with oil cap/dip stick in place, but if either are removed, the engine idles rough.

I did damage a clip on one of the hoses coming out of the PCV valve when I was trying to maneuver to the banjo bolt on the HPFP (the hose on the far right that ducks down underneath the brake booster hosing/coolant lines)- but it looks like it’s holding in place well, and hasn’t moved at all since I stuck it back on

N80 valve was replaced by a Bosch part about a month ago

Brake booster hoses look newer- I didn’t see or feel any visible cracks; no unexpected noises from that part of the engine at idle.

Cleaned MAF sensor connector, didn’t change anything

Nothing looks substantially out of the ordinary in blocks 32 or 33- if additional info is needed, let me know

Block 002 registering around 2 at idle

Block 30 might be interesting- B1S1 is constantly stuck at the same value, while B1S2 fluctuates.

Block 36 in basic settings says B1S1 OK, with a value of 1.36

Block 046 in basic settings says CAT B1 OK

Any advice on how to proceed would be greatly appreciated! Thanks for your help!

 

[Hamad990]

Check your PCV itself, there might be something wrong with it, I had a similar issue a while back and it turned out the PCV failed and needed replacing. I'll link something ROH ECHT told me, and a picture to show you how to test it.

Disconnect the PCV's corrugated tubing at the intake manifold (red circle area), wipe the oil from the disconnected end, and blow into it with force. If it seals, then the PCV is not losing boost.

If you can breath into it then the PCV will need replacing

 

[Weixb]

I just tried blowing into that hose with force, but it seems like there’s a solid seal! It’s also not difficult to remove the oil cap when the engine is running.

I’ve heard that PCV’s can fail in a multitude of ways, so I’m sure there’s a possibility it’s the culprit- this car has 150k miles on it, and since it’s new to me, I have no idea if or when the PCV was replaced!

 

[Hamad990]

Weixb Try putting back the original N80, and see if that still triggers the code.
To be honest if you don't really know when it was last replaced then it doesn't really hurt to do so, the PCV is like $60 on ECS for an OEM one and less for an after market branded one.
Another suggestion that might help is doing a smoke test to see if there's any leaks that might let in more air than the system accounted for. If that doesn't reveal anything then it might be fuel related maybe? Perhaps faulty injectors? Someone else will have to confirm that if that would actually cause that code to pop up.

*EDIT* Just reread your comment and somehow just noticed the part about the engine oil cap. From my understanding from a VW friend/enthusiast, you shouldn't be able to take the cap off easily. And if you are able to then it usually means that there's something wrong with the crankcase breather system(If I'm wrong please let me know, I'm just relaying information that he told me) and that's where the issue will lie.

 

[Weixb]

I read on the Ross-Tech site that apparently if the PCV/breather system is faulty, the engine will produce a full vacuum at idle- which I suppose means that the cap would take a ton of force to remove. BUT that being said, I've read so much conflicting information, I have no idea what's true!

Sadly, the original N80 is no longer in my possession... the code didn't start getting thrown until more than a month after I replaced it. I suppose the new valve could have gone bad, maybe it's something to check.

I think your idea of starting with PCV/N80, and moving on to a smoke test might a good place to start. Maybe there's also a chance it could be the LPFP just due to the fact that the car is taking a slightly longer time to start when it's cold?

I'm super frustrated with this darn code- the last thing I want to do right now is to start replacing random things on the car until the code goes away, especially because it looks like there's a whole laundry list of things that could be causing this problem! I might spring for a new PCV since it's not too expensive and see what happens, but fingers crossed that I'm not going to have to dig all the way to the injectors..

 

[ROH ECHT]

Through the years, what has resolved this code differs in many ways.
From a leak in the intake manifold seal.
Others, split brake booster tubing.
PCV failings or cracked PCV tubing.
A need to replace the B1S1 O2 sensor.
Dipstick o-ring not sealing.

Go back into vcds 01-engine and clear fault codes even if there are none. Then start the engine and go back to MB 032 and MB 033. Look at STFT(MB 033 block-1) and see if it is high rather than appearing low due to its adjustments. As in this vid at about 2:00:

If you do not see STFT jump to a high positive and instead it continues to bounce between pos and neg near zero, then it doesn't have a leak.

Regarding the PCV test; if while running you find the cap is difficult to open and the engine stumbles a bit when the cap is removed, then the PCV is likely fine. But if the cap seems easy to loosen and rpms do not seem to change the moment the cap is removed, the pcv is likely failed.

So, continue to check the PCV and test all you can for leaks.
And do not have it set in your mind that it will only be one issue. You may find one thing wrong, fix it, and still the code returns. This is because it may be more than one thing going on.

 

[Weixb]

Hi Roh, thanks for taking the time to post!

If I remember correctly- when I clear codes, the STFT still fluctuates between positive and negative near zero. I'm going to check it out again tonight or tomorrow. If it's high, I might get a can of carb cleaner and see if I can locate any vac leaks that might be present.

As for the oil cap- I believe that last time I tried taking it off with the engine idling, it came off with almost the same amount of effort as when the engine is off. The engine definitely runs rough when the cap is off, but I didn't check the RPM's- I'll look into that next time!

Thanks to everyone for the ideas as to where to start- I'll keep updating the post as I make progress with the problem-solving!

 

[Weixb]

All right- I did what Roh Echt recommended: cleared codes and ran banks 32 and 33 after starting the car.

The short term sensor (bank 33) was reading from 23 - 27% when I fired up the car, sat there for more than five minutes, and slowly backed down to fluctuating around zero after block 32 started registering long term trim. I'm guessing that this means I'm looking at a vac leak somewhere!

Roh- I saw a video you posted on doing a smoke test on your MK5- I'm not sure if I should approach it this way, or if you have any recommendations as to where to start. If I use carb cleaner, what's a thorough way I can check for leaks? Or should I just try to be thorough and spray everywhere? Any common failure points other than the brake booster lines near the HPFP? And if I try to smoke test on my own, any recommendations as to how to proceed? Or is it better to bring it to a shop?

Hamad- I think you might be on to something with the PCV. A question to both of you- I saw on ECS that there's a common failure point on the back side of the engine: a rear breather hose that has been updated, and ECS recommends replacing if you replace your PCV. Is this a failure point that could throw this code?

Thanks for the help guys!

EDIT: I also noticed some oil leaking from the vacuum pump near the HPFP- I'm guessing the seal is failing, and needs to be replaced at some point. Could this also be related? Sorry for all the questions, just brainstorming here!

 

[Hamad990]

Weixb is this the part your referring to?
https://www.ecstuning.com/b-genuine-volkswagen-audi-parts/breather-tube/06f103213n/

If so, then I wouldn't know if this would cause the code to pop up; my only experience with it is that it was leaking oil, since it was held on one end with zipties.

As for the smoke test, you can make a simply DIY one from some tutorial on Youtube. That's how I made mine, and it was a lot better than paying the money to get it tested at a garage.

Here's the video tutorial for the smoke maker that I use:

 

[Weixb]

Hi all, sorry to take a moment, had a very busy weekend!

I tried to do a quick vac leak test using carb cleaner- spraying anything I thought could be a culprit, however, I didn't catch any changes in RPM while spraying anything. I could definitely hear a slight hiss somewhere, but even spraying everything I could think of, I couldn't catch any RPM shifts.

I did the test that Roh mentioned, removing the oil cap while watching RPMS through VCDS. The cap removes extremely easily- and engine revs don't change that much (from a steady 720-760 RPM with the cap on, to fluctuating quickly between 680 and 800 when removed). The engine does idle very rough, however.

I remember when I first got the car that it took a decent amount of force to remove the oil cap at idle- I'm going to go ahead and replace the PCV valve and see if that changes anything.

Because I don't know if the breather hose is the latest revision- should I get the kit that updates that as well? Or is it safe to just swap out the PCV? Any recommendations on which to get? The breather hose looks fine on the car- no oil leaks coming from it.

Thanks!

Thomas

EDIT: Hamad- thanks for the link on the smoke maker- it'll probably be my next step if this PCV doesn't end up being the culprit!

 

[ROH ECHT]

All right- I did what Roh Echt recommended: cleared codes and ran banks 32 and 33 after starting the car.

The short term sensor (bank 33) was reading from 23 - 27% when I fired up the car, sat there for more than five minutes, and slowly backed down to fluctuating around zero after block 32 started registering long term trim. I'm guessing that this means I'm looking at a vac leak somewhere! Uh...yes. There is a leak.

Roh- I saw a video you posted on doing a smoke test on your MK5- I'm not sure if I should approach it this way, or if you have any recommendations as to where to start. If I use carb cleaner, what's a thorough way I can check for leaks? Or should I just try to be thorough and spray everywhere? Not a fan of the carb spray method. But if you are going to try it...yes, you'll need to spray it at every connection and down every bit of the length of all suspected tubing. Any common failure points other than the brake booster lines near the HPFP? Lots of locations can leak; MAF sensor seal. Every inlet hose connection between the MAF and the inlet ports in the head. Every tube and hose connected to the intake manifold. Seals for the VVT cover and vacuum pump. And if I try to smoke test on my own, any recommendations as to how to proceed? I use a one gallon paint can which I've attached two hose fittings to. I drop in a smoke bomb, seal the lid, and use a bicycle pump. The smoke doesn't lie. Or is it better to bring it to a shop? If you have a good shop with the smoke tester...they are often very thorough. Also, they normally do not settle after having found one leak...they'll continue looking for others.

Hamad- I think you might be on to something with the PCV. A question to both of you- I saw on ECS that there's a common failure point on the back side of the engine: a rear breather hose that has been updated, and ECS recommends replacing if you replace your PCV. Is this a failure point that could throw this code?

Thanks for the help guys!

EDIT: I also noticed some oil leaking from the vacuum pump near the HPFP- I'm guessing the seal is failing, and needs to be replaced at some point. Could this also be related? Yes, but not likely...only if the leak is bad enough to allow air to flow easily in or out of the crankcase.

Comments above in RED ↑
The updated rear breather(RBT) tube isn't going to cause a STFT addition that you saw in the test you did with VCDS. Unless the tube itself is cracked or leaks at either end.
The updated RBT is the valved RBT in my thread here; https://www.golfmkv.com/forums/index.php?threads/proper-pcv-to-crankcase-breather-tube-info.378931/