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Old 08-20-2017, 04:10 PM   #1
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need help with air/fuel mixture problems

hi guys,

2.7L 2000 boxster with 140k miles on the chassis and 35k miles on the engine

i've been having these air/fuel mixture problems on and off since i bought the boxster two and a half years ago.. who hasn't?
used to be a simple MAF clean and a reset and they would go away for a few months.


now i have a CEL that stays on and the following codes:
P1128 - Oxygen sensing adaptation idle range bank 1
P1130 - Oxygen sensing adaptation idle range bank 2
P1126 - Multiplic mixture adapt lower load range B 1
P1133 - Multiplic mixture adapt lower load range B 2
P1132 - Multiplic mixture adapt upper load range B 2 exceeds limit value

car is running fine except for a slightly bumpy idle. no power loss when i'm on it.


here's what i've done over time not necessarily because of this but to help paint the picture:
1. replaced AOS about 20k miles ago when it went bad. pretty sure AOS is fine still, no bad AOS symptoms
2. just replaced MAF with new BOSCH one (with durametric MAF showed a steady 13.6 - 14.0 kg/h at idle.)
3. replaced O2 pre cat sensors on both banks with OEM ones.
4. did a vacuum leak test at Vertex in Miami and they didnt find any leaks at all
5. i was suspecting a fuel delivery issue so i did a fuel pressure test. it stayed flat at 3.2 bar (i know the range should be between 3.3 and 3.8 bar). I would say that's not bad, maybe a bit on the low side (fuel pump being a bit tired at this mileage? maybe just the gauge was a bit off? cheapo one..). when revving and keeping it there the gauge would move slightly then be stable again under constant gas. I forgot to pull the vacuum hose from the regulator with the fuel pressure gauge on to check it but when i pulled it after it had a good sucking pressure.


when i had the durametric connected I checked the O2 sensor voltage and all looked good (ranging from 0.10 to 0.75-0.80) except for O2 sensor voltage behind cat conv bank 1 which showed a static value of 0.08 volts. after cat O2 sensors are original that came with the used engine. i plan on replacing both next so i have a full set of brand new sensors all around.

could this one O2 sensor cause the issue i'm having? i was thinking that an after cat sensor would be less important but they do all talk to the brain of the car for that perfect mixture.

i'm also thinking my fuel pressure is a bit low? what do you guys think? it's just a tad low, enough to throw more air in the mix and throw all these codes as if it were running lean. if it was lower i would probably have power losses but i'm good there.

i tend to believe the injectors are fine being low mileage (i use nothing but shell gas) and because i had these issues before and after the engine replacement but i might be wrong. I dont want to throw money at things unless i'm out of options.


what do you guys think?


thanks in advance,

Cristian


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Old 08-20-2017, 06:09 PM   #2
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I'm surprised you don't get the old P0420 code with the secondary reading basically nothing. Supposedly the secondaries don't affect the air/fuel but I am speculating that they do in the long term if it sees something it doesn't like for extended periods of time. You should be steadier on the second 02 and closer to .5v but it should still bounce around the .4 to .65 range.
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Old 08-20-2017, 06:29 PM   #3
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I would assume you have replaced the fuel filter?
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Old 08-20-2017, 06:46 PM   #4
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I'm surprised you don't get the old P0420 code with the secondary reading basically nothing. Supposedly the secondaries don't affect the air/fuel but I am speculating that they do in the long term if it sees something it doesn't like for extended periods of time. You should be steadier on the second 02 and closer to .5v but it should still bounce around the .4 to .65 range.
it doesnt move at all so that means its busted right?
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Old 08-20-2017, 06:48 PM   #5
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I would assume you have replaced the fuel filter?
first thing when i bought the car so it's pretty new. if fuel delivery is an issue it's most likely pump related or injectors
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Old 08-21-2017, 05:05 AM   #6
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This seems like a vacuum leak to me. I know you had it tested but you must check everything, and I mean everything... even the brake booster. I know I now sound like a broken record, but this was our 2 year issue with mixture issues.

Make sure you 100% have the proper MAF, these are at least 2 for the 2000MY and they are NOT compatible without an ECU flash.
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Old 08-21-2017, 05:17 AM   #7
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[QUOTE=CrisZenithBlue;547491]it doesnt move at all so that means its busted right?[/QUOTE
Either the o2 is busted or wiring to it or the plug etc... You have to go drive the car and get the cat and o2 nice and warm to get accurate readings. They wander around when cold startup and then smooth out but your seems to be dead. The smoke test is great at finding vacuum leaks but you have to stick it in several places, I even throw them in the dipstick on cars to look for PCV problems on vehicles or other gasket leaks by just slightly pressurizing and filling the crankcase.
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Old 08-21-2017, 07:03 AM   #8
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You've ruled out the air delivery everywhere, nothing jammed up that could screw up the air flow? some dead bird inside your intake tube? DME will not supply fuel if its not getting air (I think)

Luck with the find. Cant wait for my 97 to start trowing codes... looks like its going to be not-so-fun :/
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Old 08-21-2017, 08:39 AM   #9
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This experience may help...
My car is a 2000 Box S. I replaced the original MAF (996.606.124.00) with the updated MAF (996.606.125.01) and took it to a shop to have the software updated to use the new MAF. When I had the car dynoed, I had a part-throttle lean condition. Things were OK at WOT. I put a 124 MAF back in and everything was fine. It turns out that the shop had not been able to update my software.

Maybe you've got the 125.01 running with the old software.
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Old 08-24-2017, 06:35 PM   #10
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Quote:
Originally Posted by bwdz View Post
I'm surprised you don't get the old P0420 code with the secondary reading basically nothing. Supposedly the secondaries don't affect the air/fuel but I am speculating that they do in the long term if it sees something it doesn't like for extended periods of time. You should be steadier on the second 02 and closer to .5v but it should still bounce around the .4 to .65 range.
now that i think about it.. a few months ago i got the P0420 code, i reset and it never came back so i assumed the cat is fine. i never checked the O2 sensor though.

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Old 08-24-2017, 06:38 PM   #11
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Originally Posted by j.fro View Post
This experience may help...
My car is a 2000 Box S. I replaced the original MAF (996.606.124.00) with the updated MAF (996.606.125.01) and took it to a shop to have the software updated to use the new MAF. When I had the car dynoed, I had a part-throttle lean condition. Things were OK at WOT. I put a 124 MAF back in and everything was fine. It turns out that the shop had not been able to update my software.

Maybe you've got the 125.01 running with the old software.
I have the 125.01 part. I sent my VIN to Pelican and they said that's the right one for my car. it's the same one that was on the car, not the original though, it had been replaced by the previous owner.

i'm fairly sure i have the right MAF. fairly..
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Old 08-24-2017, 06:48 PM   #12
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I'm still a bit confused about the O2 reading a flat value..
is it the O2 sensor that's dead or the cat?

maybe an easy way to find out is to switch the left and right O2 sensors and see how they read? those damn sensors are about 100$ a pop..
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Old 08-24-2017, 07:21 PM   #13
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If the car is failing to supply the correct A/F mixture, its normally fair to assume that the CATS are also fried (or soon to be).

Clean your TB and air intake, run the official PIWI tests for both A & F delivery. If those tests passes then start the car and run it - not before

(if it'd be me/my car)
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Old 08-25-2017, 02:56 AM   #14
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If the cat is fried then the 02 sensor will still be working to correct the A/F ratio. It should not just sit still. You can find 02 sensors less expensive. They are literally all the same with a different plug on the end...

$62 at Rock Auto

http://www.partsgeek.com/gbproducts/SC/96050-08004161.html?utm_content=SC&utm_term=2010-2011+Porsche+911+Oxygen+Sensor+Bosch+9A1+606+124+0 0+Left+10-11+Porsche+Oxygen+Sensor&fp=pp&gbm=a&utm_source=google&utm_medium=ff&utm_campaign=PartsGeek+Google+Base&gclid=Cj0KCQjwlf_MBRDUARIsAD8Gj8BiagKDcj9H1zO8C_Dp E6njJlbl1koxO090jnzHf59PlgtS0WpBGp4aAn9FEALw_wcB&ad=47433965052
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Old 08-26-2017, 04:56 AM   #15
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Originally Posted by CrisZenithBlue View Post
I'm still a bit confused about the O2 reading a flat value..
is it the O2 sensor that's dead or the cat?

maybe an easy way to find out is to switch the left and right O2 sensors and see how they read? those damn sensors are about 100$ a pop..
That is a very good idea. Also you can test with a voltmeter. O2s actually produce voltage, it is not a signal from the computer and then a return signal like other sensors. You have the heater wires but the 2 white wires should produce voltage and you can verify that way if it is the o2 or if it is a wiring problem. I work on a lot of cars and keep plugs off old o2 sensors and scrap cars o2 connectors with extended wires so I can just plug into it and test it in a convenient location rather than underneath the car.
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Old 08-26-2017, 06:14 AM   #16
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How do you ensure its within the mV rated range? Fluid sensors needs a pretty sharp resolution to function to specs, no? Was under the impression only a computer was geared for this sort of accuracy. Mind you if one have a industrial grade multi-meter then it might be doable. Really dunno... excuse my ignorance on the subject, never done it. Interesting stuff

Warning: requires 10 mega-ohms independence multi-meter on Porsche cars (and Prius). To prevent drawing too much current and damaging the other end, something like that

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Old 08-26-2017, 05:40 PM   #17
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How do you ensure its within the mV rated range? Fluid sensors needs a pretty sharp resolution to function to specs, no? Was under the impression only a computer was geared for this sort of accuracy. Mind you if one have a industrial grade multi-meter then it might be doable. Really dunno... excuse my ignorance on the subject, never done it. Interesting stuff

Warning: requires 10 mega-ohms independence multi-meter on Porsche cars (and Prius). To prevent drawing too much current and damaging the other end, something like that

Porsche are complex things! Love it tough...
You won't get "accurate" readings with just a simple voltmeter. You can however determine if it is "dead" if you get something similar to nearly no voltage that his scanner is reading. It is a little easier to do on the secondary o2 as it's voltage should be much steadier than the fronts. If you have a fancy meter or a scope or even a high low min/max meter that is a little better. All the reading should be done after the car is warmed up, the heater circuit can malfunction on the o2 and cause problems as well.
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Old 05-09-2020, 01:00 AM   #18
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to conclude this old thread:

plot twist! i had the wrong version of MAF. i got this on Amazon and has been working flawlessly for 2 years: Bosch 0280218009 Original Equipment Mass Air Flow (MAF) Sensor

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