Driveability problem with Check Engine Light on 99

[BigHead]

This morning, I found myself standing in the paddock garage at NHIS, with a problem with the wife's 1999 996. Doh. The Check engine light came on a couple of weeks ago. I read (then cleared) the codes, hoping that it was just a burp in the system. The codes were :1123 1125 1128 1130. The light came back on shortly thereafter, and I haven't had a chance to check the codes again since.

Hadn't been a driveability problem in the intervening time, but on my way up to the track this morning, as I accelerated hard out of the tolls, with the throttle near the floor, the car stumbled badly at around 3500 rpm. Major loss of power, stumbling. I can accelerate to higher RPM just fine if I don't do it with full throttle. (Prior to this CEL coming on, I did sense a momentary hesitation at ~3800 rpm, but

that was just a very minor little, split-second pause). Just did a couple of recon laps of the track, and same problem - if I try to accelerate it with anything more than half throttle, it sputters and hesitates and lurches. I can rev the car to redline using light throttle. It was raining there, if that makes a difference.

FWIW, I did change the plugs about 2.5k miles ago, so I guess it could be a loose/bad plug or plug wire, but the CEL kinda points me in the direction of a bad throttle position sensor, O2 sensor, or MAF.

Would a bad throttle position sensor cause an O2 failure? Or is it the

other way around? Anyone know what code 1123 is? Comments about how

easy/hard it is to replace a throttle position sensor and/or O2 sensors?

. P1122 - Throttle Position Sensor 2

. P1123 - Oxygen Sensing Adaptation Area 1 (Cylinders 1 - 3) - Lean Threshold

. P1124 - Fuel Pump Relay Output

. P1125 - Oxygen Sensing Adaptation Area 1 (Cylinders 4 - 6) - Lean Threshold.

(. P1125 - Oxygen Sensing Adaptation, Upper Load Range, Bank 1)

. P1126 - Oxygen Sensing Adaptation, Lower Load Range, Bank 1

. P1127 - Oxygen Sensing Error By Means of Short Test, Bank 1

. P1128 - Oxygen Sensing Adaptation, Idle Range, Bank 1

. P1130 - Oxygen Sensing Adaptation, Idle Range, Bank 2

Last year, I had a CEL problem, related to the Mass Air-Flow Sensor. I didn't replace the MAF last time around - I pulled it, cleaned it with some alcohol, replaced it, and all has been right with the world for the last year or so. When I replaced the air filter, I found out that the prior owner had installed BMC filters, the oiling of which I suspect caused a film on the MAF. Should I try cleaning the MAF again? Or do you think it's a problem with the O2 sensors? But not because the signal isn't out of range elsewhere? Throttle position sensor?

Gosh, darn it.

Any suggestions/comments/advice would be greatly appreciated!

thx,

--Dennis

[Loren]

P1123 to 1130 are all oxygen sensors triggering over limits.

P0122 is Throttle Position Sensor - Below Lower Limit (there is no P1122 on this car).

The Oxygen sensors can not all be bad - they are all just getting bad readings. The key just may be the Throttle Position Sensor (TPS). If it is not functioning then I don't think the DME would not know where the throttle position is so it would not know how to adjust the fuel mixture. The TPS should measure 4.5 to 5 volts across the two pins when the ignition is on. If not it could be bad or the connection between the DME and TPS could be bad. Worst case a bad DME/connection at the DME.

I think you solve that P0122 code and clear the codes and see that solves it. That's my take on it...

BTW all the Carrera P-Codes are listed here

[BigHead]

Thanks (as usual), Loren!

Ok, so where is the TPS located? Is it easy to replace? How do I test it (e.g., where are the two pins located)? BTW, I didn't pull an P0122 code - I pulled 1123, 1125, 1128 and 1130, which is why I thought it might be the MAF sensor. FWIW, I just tried cleaning the MAF wire with alcohol, and went for a test drive. The car seemed MARGINALLY improved, but it could just be my imagination. If it's not the TPS, what do you think about the chances that it's a cooked MAF sensor?

Thanks,

--Dennis

[Loren]

If you did not get a P0122 then forget the throttle sensor. Most likely cause for all the oxygen sensors triggering is an intake leak or low fuel pressure. A number of these in the past have been a cracked oil separator allowing (additional) air in. Could still be a MAF, but I would have someone look at the oil separator. Most dealers are aware of this problem...

[BigHead]

Thanks, Loren. Excuse my ignorance, but what is the oil separator? And is it tucked away somewhere where I can't inspect it myself? Is there a TSB on this?

TIA,

--Dennis

[Loren]

There is no TSB on the Oil Separator - even though these have failed on a number of cars (cracked). The oil separators (there are two) are in the crankcase. To get to them you would need to remove the engine sump cover - and then reseal it after the inspection/repair. In the image below they are numbered 9 and 13 (image is 180 degrees rotated from how it is in the car).

[BigHead]

Howdy, all. Some of you might remember my problem with the wife's 1999 996 back in July. See below for the full thread.

I realized yesterday that I had neglected to post the solution to the problem, after I resolved it. With some great advice and e-mail diagnosing from Stephen Kaspar at ImagineAuto and Loren from Renntech.org, I concluded that the most likely cause behind the "check engine light" and the accompanying lose of power at higher RPM was basically just a failure of the Mass Air Flow Sensor (MAF).

Stephen wrote:

>I would say that the film is shot. The code that the car is throwing is a picked up from the 02. In other words the 02 are the eyes and the brain is picking up that something is not right. The 02 it self has a different code for out of range. When you look at this code it shows a lean under threshold which means that the control of the ECU is beyond the adjustments that are needed. This is not a problem with the 02 rather something up stream or bigger. The MAF often reads less air when bad hence causing less fuel and giving the lean condition according to the 02. The car doesn't know why since air flow at that given point doesn't not indicate it SHOULD be a problem, yet the AFR target for the map is off. The ECU tries to adjust, but is out of range. I vote a replacement MAF. FWIW I have not had good luck cleaning them.

_______________

So... I bought a replacement MAF (for $245 from Jeff at Sunset Porsche, just barely beating the price increase), and installed it myself. It took, literally, about 30 seconds. Well, ok about 45 seconds, but that's because I dropped a screw and had to look for it.

I then cleared the CEL with a really, really neat OBD-II tool from http://www.autoenginuity.com/. I actually bought it off of eBay, where the company has regular sales, and saved quite a few bucks from what they charge on the site. I got the Palm version, so I can use it more easily in the car.

After clearing the light, I went on a long drive. Car ran FLAWLESSLY. Have been back to the track twice since too, and have had no problems. So it certainly appears to have been the MAF causing the headache.

Thanks, Stephen and Loren!!!!

====

Oh, In addition to complete OBD-II functionality, the Autoenginuity tester ALSO came with an additional piece of software, "SpeedTracer", for FREE, which "is a performance analysis software for your PC or PDA. Are you curious if that new part worked? Is your vehicle performing to its fullest capabilities? With SpeedTracer, we can help you answer those questions. Save hundreds of dollars running dynos on your vehicles. What's more, you can run the performance analysis at YOUR convenience--not regular shop hours.

What it can do:

0-60ft time

0-60 MPH

1/8 mile time

1/8 mile speed

1/4 mile time

1/4 mile speed

G Forces

SAE Horsepower

Torque

SAE Horsepower and Torque vs RPM graphing

Speed vs Time graphing

_____________

All way, way cool. Of course, I haven't had the time (nor the long empty stretch of flat road) to play with it yet, but for any of you considering getting an OBD-II tool, you might want to get this as SpeedTracer appears to be a really great way to validate all of the performance mods to your car. Now you can really see if that K&N air filter or new chip or exhaust has improved your performance....

vty,

--Dennis

[diego996]

There is no TSB on the Oil Separator - even though these have failed on a number of cars (cracked). The oil separators (there are two) are in the crankcase. To get to them you would need to remove the engine sump cover - and then reseal it after the inspection/repair. In the image below they are numbered 9 and 13 (image is 180 degrees rotated from how it is in the car).

Where in this diagram is the "bellows?" I am confused as to the location and access in my '00C2 6spd.

[Loren]

This is the AOS on the top of the engine (that usually goes bad) - those other two are in the crankcase.

Item 1 is the AOS

Item 10 is the bellows.

[diego996]

Thanks! What do you think is the best way to inspect the bellows for leaks?

[rb101]

You can look up on the driver side of the transmission and see the AOS and bellows.