Good to know, along with Boxsterra's explanation. *NM*

Hi all,

It's been ages since I've posted (was more active on the old PPBB ) but just wanted to share some insights in case anyone else runs into this...

I have a 2001 Boxster that had a persistent hunting idle that I could not get rid of (began at around 55K miles). Idle RPMs would fluctuate up and down and it finally got so bad the car stalled a few times at a stop. Smoke tested the motor multiple times, replaced the MAF, all four oxygen sensors and the air-oil separator and still was getting P1126 and check engine lights. Tried cleaning the throttle body and checking all the connections on the plenum, fixing small vacuum leaks, new gas cap, new oil cap, etc. all to no avail. Finally tried installing a throttle body from a different car and the problem vanished. Replaced the throttle body with a new one and have been good ever since. If you have a fluctuating idle, you may want to look closely at the throttle body -- it appears in mine that the round gate in the middle had gotten out of alignment and was wearing into the metal of the housing around it (see photos) so it would not open/close properly. Oddly, it only threw codes for one bank... Hope this helps someone else and saves you the time, headache and $$ I spent throwing parts at mine hoping to find the cure.

John
2001 2.7 SG/GG/BK
Rockville, MD








rough idle P1126 oxygen sensing adaptation stalling check engine

plate to get out of position.

That's probably from wear.

Anyhow, good catch.

There's another possible explanation that is also quite rare and that is a converter "brick" gets plugged enough (or out of position) and impedes exhaust gas flow.

I am in the process of having the exhaust manifolds on my 02 Boxster replaced (with used exhaust manifolds) to address one converter that has a loose "brick" that rattles/buzzes and I suspect occasionally gets enough out of position to trigger a P0430 error.

... loosening the two torx screws on the plate.
This may allow the butterfly to settle back in place (if the TB hasn't worn too much. I highly doubt it has).
Once the butterfly settles in place, hand tighten one of the torx screws and remove the other one.
Put locktite on the threads and tighten in place.
Remove the other torx and repeat.

If the butterfly has settled back in place you should not see light around it, when held up to a light source, just at the place where it wore down.
The little bit it could have worn will not affect the idle, because the butterfly will still have to open somewhat to allow more air through.
Happy Porsche'ing,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

that could be because the misalignment caused turbulence that negatively affected one bank more than the other.



Edited 1 time(s). Last edit at 05/10/2014 06:12PM by Boxsterra. (view changes)

Thanks guys. Learned more than I expected yet again. I will try the fix just to see if it does the trick, Pedro. And FWIW, MarcW, I have a loose substrate brick in one of my CCs also -- so far, the worst symptom has been occasionally sounding like a Model T on an bumpy road.



Edited 1 time(s). Last edit at 05/09/2014 08:54PM by phatryd. (view changes)