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Old 12-17-2019, 05:59 PM   #1
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P1128 & P1130 Limp Mode

Iíve searched and found a few issues but I wanted to see if there was anything else I may be missing. I have been getting intermittent codes and recently under wot the car went into limp mode. Idle jumps sometimes and the car seems to surge when accelerating, like its lagging. I have replaced the AOS, MAF, plugs, coils and air filter along with cleaning the throttle body. I have also used multiple rounds of chevron fuel cleaner. Iím also showing around 0 on my short term fuel ratio but -20 on the long term with the torque app. Not sure how accurate that is with this car.

Iím wondering what the next repair should be. O2 sensors or try so a smoke test?

Last edited by Boxstersouth; 12-17-2019 at 06:32 PM.
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Old 12-17-2019, 06:34 PM   #2
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What year is it????
How many miles??
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Old 12-17-2019, 07:05 PM   #3
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02 boxster s with 85000 miles. Last oil analysis was good but I know that can be misleading
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Old 12-18-2019, 07:12 AM   #4
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Those two codes indicate that you have a lean condition that the DME can not correct.
So think to much air or not enough fuel.

I always go with simplest things first then work my way up step by step to the more complex.

So lets take the possibility of to much air first.
Look for things that could cause this.

1. Wrong signal from the MAF.
But you replaced it.
Was it the correct one for the car????

2.Vacuum leak.
You can use a vacuum gauge and do a vacuum test.
Your looking for a reading 18-19 on the gauge at sea level.
There is an adjustment to that reading as you go up in elevation.
Google vacuum tests.

3.Vacuum leak at the AOS but you replaced it.
Double check your work.

4. Bad seal at the crankcase filler cap.
The rubber seal on the filler cap can go bad.

5. The crankcase oil filler tube is known to get brittle and crack.
check for cracks.
Mine had a hole rubbed in it where it passes under the edge of the engine bay opening.

6. a smoke test may be a better way to go then a vacuum test.
But I always do my own work and a vacuum gauge is $20.00.

7. An exhaust leak ahead of the O2 sensor can cause these codes.
This is unlikely in your case because both banks are affected and this is a duel exhaust system.

If I didn't find anything on the to much air possibility I would then look at the possibility of not enough fuel.

1. You can do a fuel pressure test at the fuel rail or have it done.
That will tell you if fuel delivery pressure is within spec.
It will tell you if the fuel pump, fuel lines, fuel filter, are all good or possibly part of the problem.

2. plugged or dirty fuel injectors.

3. It is rare but you could have a faulty fuel injector relay.
Sometimes the little points inside get carbon on them and they act up.
I think they are around $10.00 at any auto parts store.


Think of any sensor as a witness to an event.
They (sensors) then tell the ECU what they see.
The ECU makes adjustments based on that (and other) witnesses reports.

It is unlikely that both of your O2 sensors are bad (giving false witness).
Because you have the same issue.(codes) for both banks. and each banks exhaust is separate from the other.

So the problem is upstream from the witness (O2 sensor). They are just reporting what they see.
Hope this makes sense.

Last edited by blue62; 12-18-2019 at 07:16 AM.
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Old 12-18-2019, 09:03 AM   #5
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1126-1128 codes on a 97 Tip. Lots of places for vac leaks. Lots of hard to inspect plastic tubes that have been heat cycled for 17 years. I finally took mine to an indy and they used a smoke generator and found it. They charged me an hour +/-$125 and problem solved. I forget where the leak was.

I suggest you get some diagnostic help before you X/O 4 O2 sensors on a guess. O2 sensors aren't cheap. Let us know how you make out.
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Old 12-18-2019, 02:00 PM   #6
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Thank you all for your response I appreciate it. Itís been doing it since I bought it so I doubt itís something I have caused replacing parts but that may also mean if I did it incorrectly it wonít be fixed.

I think Iím going to test the fuel pressure and then vacuum test. I have never been successful tracking down vacuum leaks unless obvious so Iíll probably wind up with the smoke test.
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Old 01-23-2020, 11:42 AM   #7
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Quick update. I did a smoke test and found the airbox wasn't completely sealed. Reseated it, replaced a few vacuum lines for good measure and disconnected the battery for the night. Hasn't fixed issue.

Something I didn't add before is after I fill my car up it won't start without cranking a few times. I'm starting to think my issues are fuel related. Going to check the fuel pressure next.
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Old 01-23-2020, 08:25 PM   #8
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I had the same codes a few years back and a bouncing idle speed. I have read that a failing AOS can make some odd noises... mine actually made a light hissing sound when the car was warmed up. Check it by trying to remove the oil filler cap while idling. Difficult to impossible to remove indicates a failing AOS. I was amazed at the difference with the new AOS,,, the cap comes right off. I think my AOS was failing for a long time, but it started to smoke upon starting regularly about the time the idle bounce started. It all was resolved with the new AOS.
Good luck.

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