Advice for CEL coded P1128 & P1130

[2000SoCalBoxsterS]

Originally Posted by skip_168

My theory on how the MAF sensor cleaning cures the code 1128 & 1130 is pretty simple.. the element,( the paper clip lookin' thingy..), sits in the intake air flow..

the MAF sensor is an accurate current source device in its simplist terms.. the sensor sends a current through the element which generates heat.. now as air flows over the element, it removes heat from the element which causes an increase in current to maintain the element temperature.. more air = more current..

The ECM uses the current measurement to calculate the air flow into the engine.

What I think happens to the MAF is it gets a coating of dirt, the contaminate acts as an insulator.. once it gets thick enough, it skews the airflow measurement, in other words, the element does not see all the airflow.. the result is a reading of lower airflow reaching the ECM, which injects a less fuel than actually needed.. thus runs lean...

just an engineering guess....

Great explanation. But my codes P1128 & P1130 indicate a overly Rich fuel condition.

[Topless]

Originally Posted by 2000SoCalBoxsterS

Great explanation. But my codes P1128 & P1130 indicate a overly Rich fuel condition.

Skip is right. You are running lean with 1128,1130 codes.

Maybe it's just poor translation from German to English but the description of these codes tells us the O2 sensors have detected a lean condition and the DME is trimming the mixture to add more fuel but has reached it's trimming limit (rich threshold). The wording is lousy but that is what it means. Bad MAF or vacuum leak are the most common causes when both right and left bank are affected.

[joyfrog]

If you have an oil cap that ends with a 1 than they were very prone to bad sealing if this is the case go to the dealer and pick up a newer one it should end with a 2 or a 3 I woul;d try this before fooling with anything else since its like a $20 fix and 30 seconds of your time, my dad has the same care and had the same problem as well

[Topless]

Wait a minute! Are we all barking up the wrong tree here? You have a 2000 MY 986 S? If so you have a 7.2 DME. Those fault codes are different. 1128, 1130 refer to O2 sensing idle range. This would rule out the MAF as the problem. Go to Renntech.org and search these codes for your specific car year and model. Sounds like a vacuum leak is more likely. Here is one thread for the same model range car: http://www.renntech.org/forums/index.php?showtopic=18257&hl=1128+1130+codes

[skip_168]

Originally Posted by Topless

Wait a minute! Are we all barking up the wrong tree here? You have a 2000 MY 986 S? If so you have a 7.2 DME. Those fault codes are different. 1128, 1130 refer to O2 sensing idle range. This would rule out the MAF as the problem. Go to Renntech.org and search these codes for your specific car year and model. Sounds like a vacuum leak is more likely. Here is one thread for the same model range car: http://www.renntech.org/forums/index.php?showtopic=18257&hl=1128+1130+codes

once again another code definition..

and yes, a vacuum leak can cause the same codes.. on the list of things to check, vacuum leaks are first...

and actually the DME has much more diagnostic info available than you get to see. The car manufacturers are required to follow the OBDII code protocal & comunication standard if they want to sell cars in the US, but they dont put all the info in there..

you need to have the Porsche diagnostic tools, (which are propietary to Porsche), to see all the info there is..

Of course I haven't worked with car stuff since 2000, so alot could have changed since then...

[2000SoCalBoxsterS]

Originally Posted by skip_168

once again another code definition..

and yes, a vacuum leak can cause the same codes.. on the list of things to check, vacuum leaks are first...

and actually the DME has much more diagnostic info available than you get to see. The car manufacturers are required to follow the OBDII code protocal & comunication standard if they want to sell cars in the US, but they dont put all the info in there..

you need to have the Porsche diagnostic tools, (which are propietary to Porsche), to see all the info there is..

Of course I haven't worked with car stuff since 2000, so alot could have changed since then...

Topless, according to my Bentley's service manual the codes are the same for the 7.2 DME in this case. From the research I've done in the Tech section of PCA.org the Tech's there point to the MAF or the Oil separator bellows. I also printed out the RennTech code definitions as a backup to my service manual and they are all the same. I was also confused or concerned that it might be the O2 sensors because that's what the P1128 & P1130 CEL codes mention. However, Hayjae made this very good point which is consistent with what the PCA Tech's are saying,

"The O2 sensors are just reporting the symptoms of the problem. Since they are the last sensor, there is so much upstream that could result in a O2 code. Cleaning the MAF may work, but if it doesn't, look for vacuum leaks. A vacuum leak could cause a rich condition. In addition to checking the usual tubing around the motor, check the oil cap, oil filler tube and oil dip stick. If that doesn't work, get a new MAF. It could be the air/oil separator, too."

It seems the consensus opinion from multiple sources is the MAF, Vacuum leak, and air/oil separtors also know as the oil separator bellows.

I did clean the MAF and changed my air filter at the same time. So far after an hour of driving no CEL. But I'll need to drive it some more before I feel confident that the problem has been solved.

[BoxsterLewis]

Dumb question, i used to go to Autozone and check my codes, probably cant with the Boxster huh?

[skip_168]

Originally Posted by Topless

Skip is right. You are running lean with 1128,1130 codes.

Maybe it's just poor translation from German to English but the description of these codes tells us the O2 sensors have detected a lean condition and the DME is trimming the mixture to add more fuel but has reached it's trimming limit (rich threshold). The wording is lousy but that is what it means. Bad MAF or vacuum leak are the most common causes when both right and left bank are affected.

this is the case for these code definitions.. the translation is usually done a few ways:

1. germans who don't speak english too well..
2. americans who don't speak german too well..
3. or translators who know nothing about the context of the document...

all of which equal a loss of information.. sucks for sure...

I was workin' at a Techart place when the boxsters came out.. I was the only american there, and these guys had relatives that worked for Porsche. Needless to say, we got our hands on all the boxster manuals from Porsche.. all in german..

good thing I speak german.. the untranslated books were better than anything we could get in english back then..