P1128...

2002 Boxster 2.7l. Driving in the heat (mid 90's) and downtown today and the CEL came on. What the heck is that doing on? Except for the CEL no signs of any engine trouble. Back at home I pulled the code. P1128: Oxygen sensing adaptation range 3 (cylinders 1-3) enrichment limit.

Air intake leak. Fuel pressure too low. Fuel injectors contaminated. Fuel supply volume too low.

If it is an air leak I'm not sure where it could be from. Intake system hasn't been disturbed ever. Fuel injectors contaminated? Been running Chevron for nearly 2 years now and as I mentioned after a tank or two the engine really perked up. Hard to believe there's any contamination left anywhere in the engine. Plenty of fuel in the tank.

Wonder if the fuel pump's acting up? This one has been in service since 172K miles. That was 139K miles ago. I was hoping the replacement fuel pump was going to last as long as the original one but that may be asking too much.

Anyhow didn't see anyting out of the ordinary regarding engine telemetry. Cleared the code and ran another errand and engine's running just fine.

Guess I'll just drive the thing and see what turns up.

The one time I had a p1128 (more than 8 years ago), I changed out the MAF, and the CEL never came back. Maybe clean your MAF and see if that works.

if you clean the MAF it might solve the problem. Remember to never ever touch the membrane of the sensor and to only use appropriate cleaner (e.g. MAF sensor cleaner).

The MAF is the orignal MAF though it had about a 100K mile "vacation" when I mistakenly diagnosed it as bad and replaced it. When the replacement MAF failed then I went back to the orignal MAF.

Only cleaned the MAF once and that was when I was attempting to diagnose what proved to be the 1st AOS failure. The MAF wasn't dirty and it had been in service around 80K+ miles.

Engine sure is running nice -- washed the car this AM and on the way home from the car wash the engine was just purring -- so it is hard to believe a dirty or bad MAF is the problem.

The engine oil filler tube cap is pretty new so it is not likely to be that. (It was a leaking oil filler tube cap that I mistook for a bad MAF and replaced a perfectly good MAF.)

Might plug in a data logger and let it capture the MAF reading along with the short term fuel trims and maybe intake air temperature and see if I can *catch* signs the MAF (if that is what it is) acting up.

Ultimately had to change the MAF though.

The error code (nor any other error code) has made an appearance. We have had a spell of hot weather recently (yuck) and everything has gotten quite warm: fuel pump, MAF, and so on and the engine's been just fine. I think it *knows* I'm watching it.

If I have the time I will swing by the dealer and speak to a senior tech and see if he has any ideas.

After thinking about it I'm kind of leaning towards it being the MAF. The MAF is original though it had about a 100K mile "vacation". Still the MAF's been in service roughly 200K miles. I could just order one and have it handy just in case.

it's quite easy to do. Just spray it with MAF cleaner.

and he thought it might be a dirty MAF. Kind of caught me off guard. I like to say a MAF doesn't get dirty with a properly functioning engine air filtration/intake system. This is true but what the tech said is if the engine air filter is not changed often enough it can deteriorate after a while and allow dust through and this can contaminate the MAF.

When I was using the Boxster for long road trips I was changing the air filter every year or so. Since the road trips have stopped I can't remember when I changed the air filter last but it has been a while. Didn't think it needed changing that often as it is not real dust/dirty where I live/drive. (On some road trips I encontered dust storms.) OTOH, the air filter element is real small. Can't believe how small it is.

Picked up a new engine air filter and I'll change that ASAP. Then this weekend I'll clean the MAF. I'll be sure to clean the MAF over clean white paper towels just to see how dirty it really is. Hope that's it.

and an accumulation of those particles on the MAF surface will eventually cause it to lose accuracy.

The task reminded me why I no longer like to work on cars.

Managed to remember how to get the top in the service position and unclip the 2 cables from the car to let the back portion of the top fold up to kind of expose the engine compartment area.

Found one difference between the factory soft top and the aftermarket. The factory top pivots had enough drag to once the top was folded to remain in place but the aftermarket top keep flopping down.

As expected the engine was dusty. I hate looking at the engine for that reason.

Got the air filter out. What a struggle. Of course as expected the foam sponge layer on top of the filter element proper had caught some leaves and of course in my struggle to remove the filter some of these fell into the air box. Had to wrap clear plastic wrapping tape around the handle end of a large screw driver to retrieve the couple of leaves from the air box. At my apartment complex there no electrical outlet for a shop vac and I don't have an extension cord nearly long enough to reach from my place to it just so happens the closest parking space which was open when I got home last night.

In the couple of moves since I last used it I misplaced the tube of Gummi Pflege so I had nothing to smear on the sealing foam to help the filter element slide into position.

Finally got the filter tray to slide all the way in so I could snap the spring retaining clips into position.

Got the engine compartment hard lid in place and secure then got the foam/carpeted cover in place over it and secure then the storage compartment that is accessible from between the seats.

Old filter didn't look too bad. Both the top foam layer and the paper filter element were intact. As I mentioned there was a bit of leaf trash on top of the foam but that's to be expected. My fingers picked up no dust from the air box surfaces I could reach. I didn't bother to remove the MAF as I was running out of daylight.

I'll drive the car now with the new filter in place and if the P1128 error comes back maybe clean the MAF. I don't look forward to fighting with the top and the engine compartment lids though.

Managed to beat the heck out of my arms and got the bruises to show for it. This is a real problem now because my doctor wants me to give blood at least 4 times a year. (I have too much blood (an elevated HBC reading and hematocrit reading) due to overactive bone marrow. I have no blood diseases as she tested/checked me for all of them. This excess of blood is a "middle age white man's disease".) The doctor would remove blood but she won't unless I have a bone marrow biopsy done first and I looked into this and the process hurts like the dickens. I still remember the extreme level of bone pain I experienced after I broke my right femur in 3 places and no way I'm having her drive a hollow needle into my hip bone to extract a bone marrow sample. So I refused to allow her to do the bone marrow biopsy. Then she suggested donating blood. This works real well and lowers the HBC way down below the high reading. Trouble is the last time I gave blood, back on May 6 I was almost not accepted because of the bruises on my arms. For some reason Red Cross now rejects a donor with bruises. It was clear the arms had no needle tracks -- the nurse checks for those. I told the nurse the needle used to extract blood doesn't hardly even leave a mark. She relented because she had not seen the video and was not current on this new restriction. The others there told me that any bruising sign was suitable to be rejected as blood donor.

Here I've been really careful to not bang my arms so come early July when I can next donate blood my arms will free of any bruises and danged if both aren't covered in bruises this AM. If the MAF needs cleaning or replacement this will have to be done at the dealer. I'm not messing with it here at the at house.

So now today I'll drive the Boxster to work and back and see what happens. The engine was running just fine before I changed the filter and last night driving it a bit after replacing the filter the engine felt just fine.

The improvement is about on par with the improvement I noticed after I switched the Boxster from Shell V-Power to Chevron premium.

I looked closer at the old filter today. The back -- clean -- side is intact and I banged this down on the sidewalk and saw nothing come through.

I cut away the layer of foam on the top side. Before the cutting started I noticed large areas of the foam had outlines of where leaf debris had been. I noted when I removed the old filter the large amount of leaf litter on top of the filter. In the past there have been maybe 2 small leaves but this time there were many more. Maybe as many as 10. And lots of finer bits of trash too.

All the leaves and other trash over the surface of the foam represented a large percentage of the surface area of what I note is a very small filter. (Tech had a 918 in the service bay the other day doing a 20K mile service on it. The air filters were exposed. They reside in holes in the carbon fiber tub. The filters -- rectangular panels that looked like K&N -- were huge! OBTW, be very glad you do not own a 918. The tech told me he had 60 hours of labor in the 20K mile service. To get at the plugs much of the back of the car was removed and considerable engine hardware has to be removed.)

After I cut away the foam I turned the element upside down and smacked it on the concrete a couple of times and the amount of black dust -- almost coal dust black -- that came out was rather striking. The filter I think was full. A side note: The dust being so dark which is rather surprising because most "dust" is silica which is a light colored material and I have not driven the car in dusty areas for years. I have to wonder if the bulk of this "dust" is rubber dust? My work commute has me on I-580 which is the main east/west freeway of the SF bay area and this freeway carries a lot (and I mean a lot!) of traffic. Passenger vehicle traffic but also a huge number of big rigs.

With all the leaves and the dust in the filter I would not be surprised air flow through the filter was compromised and this explains the improvement in the engine's running. Be interesting to see if gas mileage improves any.

In the meantime I have a data logger connected that is gathering speed (every second), and intake air temperature, air flow rate, and bank 1 and bank 2 short term fuel trims (at 5 second intervals). At some point I'll look this data over to see if I can see any signs of a MAF problem, assuming the CEL doesn't come back on with an error code that possibly points to the MAF.

Car's been running like a dream since the air filter replacement.

(There has been an on again off again car locking issue which appeared before the P1128 error code a few weeks ago. Apparently with a passenger in the car, but not every time a passenger is in the car, the in dash door lock button activates itself, the lock LED comes on by itself. If I push the unlock button the LED goes out then comes right back on and the interior lights blink and the horn sounds twice. The cabin floor is dry. The door bottoms are dry. There are no other signs of any electrical or security related problems.)

I have not touched the MAF.

Connected a data logger to log some telemetry I thought might be of some value. Downloaded the data the other day and looked through it and saw nothing out of the ordinary. 'course, the P1128 error remained absent this whole time.

Removed the data logger and installed another type of trip logger (non-OBD2 type) and all was well.

After work last night gave a co-worker a lift to the BART station. After leaving the BART station and making my way on surface streets to the freeway at some point noticed the CEL was on. There had been no untoward behavior from the engine. The CEL was dark then it was lit. Just like that. At home removed the non-OBD2 trip logger and installed the OBD2 data logger which automatically reads any error codes. Downloaded the data from the data logger and the error code was P1128. Armed the data logger to clear the error code and later decided to make a grocery store run. Plugged in the data logger and started the engine but the CEL was dark immediately at engine start, but not from the data logger I had just plugged in. The data logger takes a few seconds to establish communcation with the car's DME and then transmit the clear error codes message. Apparently the DME had extinguished this on its own.

Guess I'll leave the OBD2 data logger in and leave it in in the case of another P1128 and then maybe the data before, during, or after the CEL event might prove helpful/informative.

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MarcW
Car's been running like a dream since the air filter replacement.

(There has been an on again off again car locking issue which appeared before the P1128 error code a few weeks ago. Apparently with a passenger in the car, but not every time a passenger is in the car, the in dash door lock button activates itself, the lock LED comes on by itself. If I push the unlock button the LED goes out then comes right back on and the interior lights blink and the horn sounds twice. The cabin floor is dry. The door bottoms are dry. There are no other signs of any electrical or security related problems.)

.

Marc, that sounds a lot like the electronic portion of the ignition switch. Any difficulty with turning / removing your key from the ignition?

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Guenter in Ontario

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MarcW
Car's been running like a dream since the air filter replacement.

(There has been an on again off again car locking issue which appeared before the P1128 error code a few weeks ago. Apparently with a passenger in the car, but not every time a passenger is in the car, the in dash door lock button activates itself, the lock LED comes on by itself. If I push the unlock button the LED goes out then comes right back on and the interior lights blink and the horn sounds twice. The cabin floor is dry. The door bottoms are dry. There are no other signs of any electrical or security related problems.)

.

Marc, that sounds a lot like the electronic portion of the ignition switch. Any difficulty with turning / removing your key from the ignition?

No. No sign of any ignition switch troubles. The switch isn't original. It was replaced a few years back when the engine refused to start -- no crank -- even after I replaced an obviously bad clutch safety interlock switch. The tech tried to get the switch to fail on the service department drive but was unable to. I insisted on its replacement and he obliged me then afterwards when he hanned me the old one he reported the switch didn't look bad. He was right. Afterwards when the no start behavior reappeared he either replaced the new clutch safety interlock switch with a new one (there were reports of a bad batch of these) or adjusted the bracket to ensure the switch was properly closed when the clutch pedal was depressed or maybe he did both. I can't recall now. All I know is the failure to start (no crank) is a very very rare event now and comes about only when I fail to fully depress the clutch pedal.

For the door lock behavior I'm liking something in the passenger door. The door lock assembly/controller was replaced a few years ago then the window regulator. I don't think the door latch switch has been replaced on that side. My recollection is it was replaced on the driver side along with the window regulator.

Next service I'll speak to the tech about the behavior and see what he advises. He can probably query the security system for any codes and from these have a good idea of what's going on.