Help! CEL and Lean at Idle Fault Codes

[Far M]

Hi all,

 

Late last week the Check Engine light & message lit up on the dashboard of my 2007 Boxster (base 2.7, 5-speed manual, 99k miles). This was a surprise, as I hadn't perceived any issues at all with how the car was running. I read and cleared the codes in Durametric to see if they'd come back: P2189 (x2) and P2187 (x2).

 

Sure enough, after some spirited driving, the CEL came back. This time, I noticed that my engine seemed a little rougher at idle, and that when I went to neutral and rolled to a stop, my RPMs tended to "surge" into 1k+ territory for a bit. Checked again, and the same codes are present in Durametric. I saved the freeze frame data, which is attached. I am a little puzzled because the fuel trims look fine(?), but I suspect I'm misreading somewhere and/or the freeze frames don't tell the full story. The car does smoke a little on startup, but I understand that to be typical for these cars, especially at this age and mileage.

 

For background, I did do a lot of work on the car (clutch, flywheel, transmission fluid, AOS) less than 1k miles ago.

 

Everything I've read is suggesting some sort of vacuum leak somewhere -- i.e., engine taking in more air than it's supposed to be. I did check my oil cap, which seemed fine. When I tried to remove the cap with the engine running, I got only a bit of resistance and the engine ran rougher, so I don't believe I have a ton of negative crankcase pressure or anything like that (I do have a new AOS after all, although I suppose another possibility is that I installed it incorrectly, leading to an air leak).

 

Is there anything left to do here before having to take it to a shop and get the intake smoke tested? Thanks.

 

freeze frames.pdf

Edited June 23, 2022 by Far M

[JFP in PA]

Both codes point to a vacuum leak at idle:

 

P2187 Oxygen Sensing Adaptation, Idle Range, Bank 1 (RKAT1) - Above Limit
P2189 Oxygen Sensing Adaptation, Idle Range, Bank 2(RKAT1) - Above Limit
Possible fault cause
- Incorrect main charge signal
- Intake air system leaking
- Fuel pressure too low
- Volume supply of fuel pump too low
- Mechanical fault in injection valves
- PCV valve leaks
- Cap of oil filler neck leaking
- Leaks in exhaust system
- EVAP canister purge valve mechanically faulty (hangs open)
- EVAP canister purge valve output stage faults

 

As you replaced the AOS, I would start by checking the oil cap vacuum at idle:

 

 

• M96 & M97 Nominal crankcase vacuum is -5.0" (-4.0"  to  -6.0") of H2O (not HG).
• MA1 Nominal crankcase vacuum is -15.0" (-14.0"  to  -16.0") of H2O (not HG).

[Far M]

1 hour ago, JFP in PA said:

Both codes point to a vacuum leak at idle:

 

P2187 Oxygen Sensing Adaptation, Idle Range, Bank 1 (RKAT1) - Above Limit
P2189 Oxygen Sensing Adaptation, Idle Range, Bank 2(RKAT1) - Above Limit
Possible fault cause
- Incorrect main charge signal
- Intake air system leaking
- Fuel pressure too low
- Volume supply of fuel pump too low
- Mechanical fault in injection valves
- PCV valve leaks
- Cap of oil filler neck leaking
- Leaks in exhaust system
- EVAP canister purge valve mechanically faulty (hangs open)
- EVAP canister purge valve output stage faults

 

As you replaced the AOS, I would start by checking the oil cap vacuum at idle:

 

 

• M96 & M97 Nominal crankcase vacuum is -5.0" (-4.0"  to  -6.0") of H2O (not HG).
• MA1 Nominal crankcase vacuum is -15.0" (-14.0"  to  -16.0") of H2O (not HG).

Thank you sir. I unfortunately do not have a manometer, so I may just have to take it to a shop. Sigh…

[JFP in PA]

A quality digital manometer can be found on Amazon for less than $40, and is an excellent addition to any toolbox.  A short length of hose, a barb fitting (Amazon), and a spare or used oil cap and you are in business.  With all the AOS problems these cars have, long term it will save you $.

[Silver_TT]

^THIS

 

Gotten tons of good advice from JFP over the years but this is one of the best bits.  Super useful to have for a Porsche engine, or really any engine and especially the newer DFI engines that run higher vacuum spec levels.  All you have to know is the spec vacuum for your engines....

 

I built this exactly like JFP says to help a friend track down an oil consumption issue and to show folks in the Audi community that a PCV is doing more than regulating crankcase vacuum (it has several non-return valves and a combi valve which can fail, which can lead to increased crankcase pressure and routing too much blow-by into the turbo).

 

Keeping an eye on your crankcase vacuum is very easy to do, taking literally under 1 minute 

Edited June 24, 2022 by Silver_TT