Good Q&A on Engine Codes P1128 & P1130
 

I saw this good Q&A today, and thought I would post it here for someone's future reference if doing a code search.

Here it is:


QUESTION:

DME indicated air/fuel mixture problem.
This came on after I ran Syntech feul injector cleaner.
I changed my fuel filter since and the engine light went off then came back on within 15 miles.
-
I talked with someone who had a problem with another car but syntech cleaner & they had to replace their oxygen sensor.
Any suggestions?
Thank you

ANSWER:

These faults are do the system has reached its maximum threshold to compensate for a lean system. This can be caused by either a bad or dirty MAF sensor in which you can clean or replace. Perhaps an intake leak in which would most likely be at the oil separator bellows. The last and not as common problem would be low fuel pressure or dirty injectors. I would get some good quality electronics cleaner and clean the MAF first. After that then you can get under the car and check the oil separator bellows for deterioration.
Scott Slauson - PCA WebSite - 2/12/2006

Hi,

Interesting post, but the reply doesn't seem to consider the Lister's Cause and Effect.

I suspect that given the other person's similar experience with the same product, that it has something to do with the Injector Cleaner they used. That this Cleaner either has substances which contaminated the O² Sensors reactive Ceramic, or burned much hotter, ruining the Heating Coils in the Sensors.

Subsequently, more Exhaust elements were able to condense on the Sensors rendering them incapable of producing an In-Spec electrical signal. The DME then interpreted these Off-Spec signals as a Lean Condition and one which exceeded it's maximum allowable threshold, triggering the CEL. In other words, I don't think he's running Lean, I believe that his DME has been tricked into thinking he's running Lean. Before I went tearing into the Bottom of the Engine, I would 1st eliminate this as a possible cause.

To be sure, dirty MAF or the introduction of additional, Unmetered, Air would cause a Lean condition just as the respondent states, but I don't think that's where the problem lies or the solution will be found. 'Course, either of us could be Right, or Wrong...

Happy Motoring!... Jim'99

Good info. I have a 1128 code on for the last few weeks. I have cleaned the MAF and reset the code... It came on about 1 week later again. History on the car is I have installed an Evo Cold Air Intake kit in September and changed the exhaust to B and B at the same time. No problems till about a month ago. I have suspected a fuel pressure problem at idle sometimes as I have a noisy or whining fuel pump. The car has 25 k miles on it and seemingly no service issues. The last thing I can do on my own is disconnect the battery to have the computer re-learn the mapping and hope for the best. I have run some fuel injector cleaner not too long ago and am not sure if this contributed to my CEL or not. It is frustrating even for me and I am in the auto repair business! My next stop is to a great local Porsche shop... Brother to Brother. Hopefully, they can check my fuel pressure/ injector situation and if no other problems are found, reprogram my engine management system to compensate for the increased airflow from the Evo intake.

Sounds kind of pricey!
I will keep you posted.

I had both CEL for 1128 and 1130 after filling up; possibly having bad fuel at the local Chevron or due to a Octane Booster. After reading many threads, it seemed the problem might lay somewhere else. I tried cleaning the MAF and the throttle body, checking for vacuum leaks with little improvement. I ultimately replaced the MAF, erased the codes and the engine runs better. However I am currently experiencing a idle problem. It goes from 700 to 800 with the ac off and at idle. I thought I might just be paranoid but then the revving effect started happening when stepping on my clutch at low speeds. The revving occurs after every 2 - 3 stops. Now I am freaked out :eek: . I am in 1st and I am slowing down to a stop and disengage the clutch and the car revs to 1500 rpm. Help Please. Can it be due to my o2 sensors?

How many miles are on your car? And what year is it?

2000 S with 42k

For me: P1128 + P1130 = dirty MAF
 

CEL with P1128 and P1130. I decided to reset the codes to make sure they weren't a fluke, drove it some more and they came back on again. Everything seemed fine. I reset one more time to be sure. And slowly but surely I began to get a little hesitation when revving the engine. So I cleaned the MAF, hoping like mad I didn't need to start replacing O2 sensors, and lo and behold the engine ran like a dream.

Not really sure why it had a problem, stock air intake and from what I can tell, the previous owner must have replaced it already.