1128 and 1130 will be on my gravestone
 

I don't get it.

To recap my issue, I've had intermittent 1128 and 1130 codes since I bought the car in October. Thought for sure it was the AOS, so I had it replaced like first thing. I also bought a new gas cap at this time to try the cheap fixes first.

Code came back, so I suspected vacuum leak. Car bounced at startup before running fine, but I also had an oil leak issue that I figured was spark plug tubes. Replaced tubes, plugs. Had the car in the shop and my guy found no vacuum leak, but found high resistance on one of the O2 pre cat sensors, so replaced it and the numbers went back to normal. Cleared the codes. No code return, but he stated my MAF was reading within range but very low on the range and that I may want to replace it. I did and the code came back. So I forgot to reset the ECU when I replaced the MAF, figured that was the cause, pulled the battery, reset it and all was well.

Car was at this time running better than ever, no idle issues, awesome throttle response, MPG was best it had ever been. Took the car on an 8 hour drive to the Ozarks this week and had no issues! Flawless. That is until we were driving on some hills at slow speeds and of course, 1128 and 1130 come back again. No symptoms. Engine runs great. Made the trip back another 8 hours with that ugly yellow light glaring at me but ZERO symptoms.

What do I do next? I was going to try a new oil fill cap just to rule that out. I feel as though if it was my oil fill tube, I would've found the leak. Is it possible a small valve cover leak would cause the code? It can't be fuel pressure or I'd notice, right? It can't be the AOS or I'd have smoke and the other symptoms and I have a 6 month old AOS. I feel a vacuum leak would give me idle issues!

All that I've tried:
New Tubes
New J Tube
New AOS
New MAF
New Gas Cap

Where do I go from here? I'm seeing Check engine lights in my nightmares...
2002 2.7 88k miles. Any help is greatly appreciated.

OK, what I am about to say may start a firestorm, but here goes. On an early car (1998-1999) with a 5.2.2 DME, P1128 and 1130 are signs of an air leak (the mixture is so lean that the DME cannot compensate). On a later car, however, with the 7.2 or 7.8 DME, the same two codes indicate an overly rich mixture (MAF issues, fuel pressure too high, leaking injector, EVA purge valve issues). I'd start by checking the car's fuel trims to see where you really are.

It is very easy to start chasing your tail on these two codes........

Hi,

well first for DME 7.8:

P1128:
360 Oxygen Sensing Adaptation, Idle Range, Bank 1 - Below Limit, 360 Oxygen Sensing Adaptation, Idle Range, Bank 1 - Above Limit

P1130:
361 Oxygen Sensing Adaptation, Idle Range, Bank 2 - Below Limit, 361 Oxygen Sensing Adaptation, Idle Range, Bank 2 - Above Limit

360 Oxygen sensing adaptation idle range, bank 1
361 Oxygen sensing adaptation idle range, bank 2

Means the problem is reported at idle - so to say at very low revs.

Do you have a modified exhaust system? Did you check if your exhaust system has no little leak - especially manifold and monifold bearings?
Where both lambdas replaced, or only one?

Regards
Markus

Thanks for the responses guys. JFP, that's a little chunk of info that I haven't heard before. Makes some sense actually. Car always smells rich at startup.

Only one of the O2 sensors was replaced...should I replace the other pre cat one and see what difference that makes? I don't have a durametric but I'll try and get some fuel trim data. Is it possible that all four o2 sensors need replaced?

JFP, regarding the leaking injector, is there an easy way to tell which one would be leaking? the fact that I've got both 1128 and 1130 means it would have to be at least one on each bank right?

Exhaust leaks I don't know. I don't think so, still with the stock exhaust, and I don't hear what would sound like an exhaust leak to me. Thanks again for the info, nice to have some new theories. I really have been chasing my tail here...

jdraupp, if I may jump in here, you should replace all the O2 sensors at the same time because it makes the computer go haywire when one is dull and the other is clean and super-sensitive.

When I read the code numbers on your thread title I instantly thought oxygen sensors.... had the same issue about two years after buying my car.

When the sensors are going out, the computer can get confused and tell you it's a fouled MAF or something else. My tech smiled when he hooked up a PST tool to my car... he turned to me and said, "The car is lying to us. My bet is that it's not the MAF, but an O2 sensor. Replace all four and I bet it will clear it up and you'll get a lot better performance out of the motor as well.

JFP may have better or different advice.

I had those codes intermittently off and one, along with a code that the heater on one of my post cat O2 sensors was failed. I also would get cat inefficiency codes, I got them for both sides.

I cleaned my MAF and put a new air filter. 1128/1130 came back.

Then over Christmas I replaced:
The one post cat O2 sensor
Plugs, tubes, and O-rings
new fuel filter

And the codes are gone. (I should mention that my gas/oil/coolant caps are all new as of a year or two ago)

I am not sure what happened, or which of these things resolved the 1128/1130 but they are gone and have never come back. A fair amount of oil was seeping out of the Spark plug tube O-rings so maybe some air was getting in? I don't know (and it sounds like you did the plugs/tubes) but that was my guess for mine. But 1128/1130 is also fuel related, maybe the fuel filter? Maybe it was the bad post cat O2 sensor throwing everything else off. Even though that sensor shouldn't be involved since it is only there to monitor the cat.

Good luck!

jdraupp:

Could you please provide us with the DME version of your car and the production date. There were some changes in the emission control system from 01 to 02.

Im with RandallNeighbour. If you chance 02 sensors, please do it always pairwise. Best is to change all at once.

Regards

You can't suck air in through the spark plug tubes.

They simply allow passage through the cam housing to the heads.

Oil leak yes, but the effect is only a mess (unless it degrades the coil pak)

Mike

If you have a leaking injector, it should show up both in your fuel trim values and by looking at the plugs.

I'm not a fan of swapping out O2 sensors unless they check out poorly. They can be tested in place using the Durametric system. These things are too expensive to change out unless they actually need to go.

My car was built in may of 2002. Not sure where that puts me, but I'm guessing DME 7.8?

Not having a durametric I can only go on what my indy said about my O2 sensors at the time and that was that the two pre cat sensors were not reading the same and the one he replaced showed high resistance. He recommended replacing the pair, however I opted to replace only the one that needed it the most as he was using Porsche o2 sensors and at 350 a pop, I figured I'd rather do the one and swap a bosch sensor in later at 88 bucks for the one that was not replaced.

My fuel trims are about normal. At idle, I'm seeing values between -3.0% and 3.0%. I don't have any fancier values than those, but I'm guessing they should be around that. However I should mention that at startup I initially got some sensor readings at 17 or 18% which I believe indicates lean? Is this normal on a cold start? When the car warms up and regulates idle the trims return to near zero?

I should also add this code does not show up until approximately 400 miles later. Both times this happened it was a long long drive and many starts before the code appeared. Removing oil cap on warm engine causes idle to change and car to bounce a bit, so can I assume that my vacuum system is in order?

Have you tried pouring some Techron into the tank and driving it like you stole it for a couple of hours?

That sounds like fun. I may just try that.

I don't know how you are determining your idle adaption fuel trims, but here is a good example of an early Boxster recently discussed here:

http://986forum.com/forums/uploads01...1401901370.jpg

It is not unusual for a code, particularly an emissions code, to show up only after some miles. The code is actually resident as "pending" until the DME is sure it is for real.

JFP, that's the number I got from the fuel trim sensor (short term) using Torque Pro with the blue tooth ELM 327. Is there something else I should be looking for?

@ jdraup:

Hard to say if you have a DME 7.8, or a 7.2. but i think will be a 7.8. There are some differences between US market and EU market. And to be honest I'm more into EU specs and have to do a little more research about US specs.

I think your car doesn't have is a seperate fuel filter that can be changed seperately. This is an integrated part of the the fuel pump since Mj 2002.

I'm with you when it it comes to original Porsche spare part prices. In general they are you relabeled and have the same quality specs. So i would go with Bosch or other quality replacement parts instead of original Porsche parts like Bosch, BERU etc.

If you remove the oil cap and the engine idle bounces a little bit and is rough - that's normal, because the vacuum system has a so to say leak while the oil cap is removed.

Maybe it's best to observe the error codes for some miles and clear it when it comes again. If it shows up too often i would change the 2nd o2 sensor. Because it's an error at idle revs i don't think that will harm anything enginewise. So it's more or less an emission problem. Nothing that really can harm the engine. Nothing that should be written on your gravestone, or from what you should get any grey hairs. ;)

General sensor values seems to be OK to me. Mine's are little different - have a EU car and a S version.

@JFP in PA:
Absolutely with you only to change parts that are broken. But in the case of o2 sensors it's really better to change pairwise, because the DME can generate errors even if the old o2 sensor is working within given specs.

Regards