Loss of Power after AOS Change

[jnicholson30]

Hi All,

Just wrapped up putting in a new air/oil separator (AOS). The good news is that there's no more smoke. The bad news is that it's now losing lower at 5500 RPM. I also feel it's idling a little rougher, though only slightly.

I did not do the major surgery version, removing the throttle body etc. Just disconnected the AOS from above/below and swapped it out. Screws are seated tightly. Anyone run into this before? Any thoughts?

Any ideas would be greatly appreciated. Thanks!

Jeff

- 2000 Boxster S, Arctic Silver / Black

[Flavor 987S]

The failed AOS may have damaged your MAF sensor. Trying cleaning and/or replacing.

[Pdwight]

Use cleaner designed for MAF cleaning...not just anything

[jb92563]

I'm experiencing something similar.

Look here to see what is going on:
how-diagnose-resolve-engine-issues-using-durametric

None of the replacements have corrected my hesitation issue.

Still no positive proof of what has happened and the exact fix, but my latest idea after replacing a bunch of stuff is that the computer needs a reset and 25+ miles of driving to re-adapt itself and run properly and smoothly.

Have not had the chance to do that yet.

What codes are you getting?

First look should be the MAF and airleaks in the induction or exhaust header.

A reading of the codes and LTFT , STFT (Fuel trim) values are helpful when trying to solve mysteries.

[jsceash]

Check the hose between the AOS and Plenum and the 4,5,6 bank and AOS there are 2 O-rings on each that I would replace anytime I remove that tubes. Then check the other tubes for a vacuum leak. Also the long hose between the 4,5,6 bank and AOS can get dried out and crack sometime when pulling it around.

[jnicholson30]

Hi All,

Thanks for your suggestions. Picked up some MAF cleaner and will do that shortly. Rechecked the connections. I do see something that looks like it could be an issue? I see a red rubber o-ring on the lower "input" next to the 2 bolts. I don't remember seeing one of these outer rubber o-rings on the old one. Does this look right in the images below?

I am wondering if (A) that could somehow be the o-ring that belongs inside and it didn't slide in; (B) that should not be there and I should reinstall without it; or (C) it is correctly installed.

Any thoughts?

Jeff

[jnicholson30]

Still have the issue. Though now, the check engine light has come on. I have ordered a ODB code checker and will update when I see the codes.

Some "good news" in that, as you could see in the first picture, the one AOS tube at the top was not seated correctly. A refitted and it took care of the slightly rough running. But not the loss of power. I still get the sense it is a loss of suction. Not sure where though. I looked around based upon the helpful suggestions but could not see anything additional jump out. Could it be the lower "input" I reference in my post below? Also, I will repost the pictures as they seem to have sized oddly.

- Jeff

2000 Boxster S, Arctic Silver / Black
Work performed: Air/oil separator (AOS), alternator, fuel filter, spark plugs & tubes, serpentine belt, throttle body cleaning, aftermarket passenger airbag switch

[jnicholson30]

Hi All,

Reposting... I do see something that looks like it could be an issue? If you have a look at the pictures in my prior post below, there is a red rubber o-ring on the lower "input" next to the 2 bolts, visible when installed. I don't remember seeing one of these outer rubber o-rings on the old one. Does this look right in the images below?

I am wondering if (A) that could somehow be the o-ring that belongs inside and it didn't slide in; (B) that should not be there and I should reinstall without it; or (C) it is correctly installed.

Does anyone have any thoughts?

Jeff

[jb92563]

Originally Posted by jnicholson30

Hi All,

Reposting... I do see something that looks like it could be an issue? If you have a look at the pictures in my prior post below, there is a red rubber o-ring on the lower "input" next to the 2 bolts, visible when installed. I don't remember seeing one of these outer rubber o-rings on the old one. Does this look right in the images below?

I am wondering if (A) that could somehow be the o-ring that belongs inside and it didn't slide in; (B) that should not be there and I should reinstall without it; or (C) it is correctly installed.

Does anyone have any thoughts?

Jeff

My red rubber seal looks like that as well peeking out a little, but I am also having the hesitation and wandering idle.

I got my replacement AOS from Pelican but I did a smoke test for air leaks and nothing is getting past that red seal so I think its fitted perfectly.

[jnicholson30]

Hi All,

Thanks for your suggestions. I picked up an OBDII scanner and have the diagnostic codes now.

Also, I cleaned the MAF and re-fitted the AOS. I was able to get the red o-ring farther in, but not completely as I imagine it may have stretched due to being in the prior position. Am thinking of changing the o-ring entirely just to eliminate the variable - a royal pain.

The code I was getting was: "P1411 Secondary Air Injection System". Some other data that came out of the scanner (thanks for the suggestion of STFT/LTFT jb92563):

Engine RPM: 732
MAF Airflow Sensor (g/s) 6.00
Commanded Secondary Air Status OFF
Short Term Fuel Trim - Bank 1 (%) -10.9
Long Term Fuel Trim - Bank 1 (%) -0.8
Short Term Fuel Trim - Bank 2 (%) -10.9
Long Term Fuel Trim - Bank 2 (%) -0.8

Oxygen Sensor Output Voltage Bank 1 - Sensor 1 (v) 0.730
Short Term Fuel Trim - Bank 1 - Sensor 1 (%) -10.9
Oxygen Sensor Output Voltage Bank 1 - Sensor 1 (v) 0.725
Short Term Fuel Trim - Bank 1 - Sensor 2 (%) - N/A
Oxygen Sensor Output Voltage Bank 1 - Sensor 1 (v) 0.715
Short Term Fuel Trim - Bank 2 - Sensor 1 (%) -9.4
Oxygen Sensor Output Voltage Bank 1 - Sensor 1 (v) 0.705
Short Term Fuel Trim - Bank 2 - Sensor 1 (%) -99.2

Not sure if I should be worried about that N/A and 99.2 in the data. There is more data available but these looked to be the most important based upon jb92563's suggestion. I took the car out for a quick 5 min drive and there does seems to be a bit more power in the mid RPM range (perhaps for the MAF cleaning?) but there is still some loss of power at 5,000 RPM and up.

Will drive it more and see if the code comes back. In the meantime, if anyone has any suggestions on what might be up please let me know. Thanks.

Jeff

----------------------------------------------------------
2000 Boxster S, Arctic Silver / Black
Work performed: Air/oil separator (AOS), alternator, fuel filter, spark plugs & tubes, serpentine belt, throttle body cleaning, aftermarket passenger airbag switch, MAF cleaning