CEL and P1123 and P1125

[nick49]

I've done a search and the amount of info is a bit confusing at best.

I've had my '99 996 going on 6 years and replaced the MAF about 3 years ago when I got a CEL with codes P1123 and P1125. Everything has been fine since until a few months ago and now I'm getting the same codes again. I did have a replacement motor installed by Porsche about 2 1/2 years ago when a sleeve slipped on my original. I have the stock air filter, recently changed the oil filter. New motor has about 12k miles. When the CEL came on with P1123 and P1125 I developed a momentary hesitation between 5-6k RPM and a low and somewhat fluctuating idle speed. I recently installed and aftermarket MAF and cleared the codes. The car ran noticeably better with higher idle and no upper midrange hesitation but the CEL came back on the first time I drove it within 15 minutes.

I verified the codes and they are P1123 and P1125. Another thing I've noticed a slight burned chemical smell when I use my heater that I didn't notice last year. It's not exactly like coolant or oil but it's possible. The coolent reservior was replaced along with the motor. The underside of the chassis and motor is clean and dry without evedence of leaking oil or coolant. The TPS looks like a new unit as is the throttle body, spark plugs, coils and related stuff supplied with the motor.

I don't have any durametric tools, just a code reader and volt/ohm meter. Any ideas as to what my be causing my CEL? Or what things I can check next? What are the simptoms of the air/oil separator billows? And is it included with the new motor? As I understand it, the codes I have mean there is a rich condition on both banks that cannot be leaned out. Is this correct? I'm hoping someone has been thru this and help me out.

TIA, Nick

[RFM]

All the parts on the engine are new, inclusive AOS and bellows, only the airco compressor is reused. Are you sure about the MAF part #?

[1999Porsche911]

If you had a bad separator you would run lean, not rich like you are. A scanner would be the easiest tool to identify your problem. It's possible you MAF is dirty and over reporting airflow causing your rich condition. You may try removing and cleaning the MAF and the contacts with an electronics spray cleaner. This will remove any contamination and reduce the reading of the MAF.

[nick49]

If you had a bad separator you would run lean, not rich like you are. A scanner would be the easiest tool to identify your problem. It's possible you MAF is dirty and over reporting airflow causing your rich condition. You may try removing and cleaning the MAF and the contacts with an electronics spray cleaner. This will remove any contamination and reduce the reading of the MAF.

I cleaned the 3 yo/15K mile MAF twice a couple of months ago and it made no difference, Then I replaced it with a new one, car runs fine now but CEL reappeared. New one has less than 50 miles on it, CEL on again and same 2 codes are present.

[1999Porsche911]

If you had a bad separator you would run lean, not rich like you are. A scanner would be the easiest tool to identify your problem. It's possible you MAF is dirty and over reporting airflow causing your rich condition. You may try removing and cleaning the MAF and the contacts with an electronics spray cleaner. This will remove any contamination and reduce the reading of the MAF.

I cleaned the 3 yo/15K mile MAF twice a couple of months ago and it made no difference, Then I replaced it with a new one, car runs fine now but CEL reappeared. New one has less than 50 miles on it, CEL on again and same 2 codes are present.

Codes indicate running rich on both banks. Could be too much fuel pressure, leaking injectors or EVAP canister purge valve open. These codes are only generated at idle. A scanner, as I said earlier, would give you a better idea of what parameters are out of wack. Just because the MAF is a new one does not mean it is working. What is the part number of the MAF?

[nick49]

New MAF is the 123.00 for mechanical throttle. And the new one made my car idle slightly higher and smoother and eliminated the hesitation at 5-6K rpm. So I assume it's working.

Are you refering to a Porsche scanner that I'd either have to purchase or visit the dealer?

Thanks

[1999Porsche911]

New MAF is the 123.00 for mechanical throttle. And the new one made my car idle slightly higher and smoother and eliminated the hesitation at 5-6K rpm. So I assume it's working.

Are you refering to a Porsche scanner that I'd either have to purchase or visit the dealer?

Thanks

There are several scanners available for < $250. It's a must have tool for all modern engines and can pay for itself with one use. Search and you'll find several that people use.

Idle control valve should not cause those codes, but if you have not done so, remove it and clean it and the throttlebody.

[nick49]

New MAF is the 123.00 for mechanical throttle. And the new one made my car idle slightly higher and smoother and eliminated the hesitation at 5-6K rpm. So I assume it's working.

Are you refering to a Porsche scanner that I'd either have to purchase or visit the dealer?

Thanks

There are several scanners available for < $250. It's a must have tool for all modern engines and can pay for itself with one use. Search and you'll find several that people use.

Idle control valve should not cause those codes, but if you have not done so, remove it and clean it and the throttlebody.

I saw the Durametric scanner for just under $300 which is Porsche specific. What would you recommend for a more reasonable price? I've got more time than money right now as I'm in the off season of a seasonal business.

I removed the air filter housing a month or so ago, inspected the filter, hoses, clamps and related parts. The throttle body with less than 12k miles still looked new. I guess I could check again.

Also if an injector was leaking it would have to be more than one or at least one on each bank to cause both codes, correct? Rather unlikely on a 12k mile motor? I think so, but I'm not an expert.

[1999Porsche911]

New MAF is the 123.00 for mechanical throttle. And the new one made my car idle slightly higher and smoother and eliminated the hesitation at 5-6K rpm. So I assume it's working.

Are you refering to a Porsche scanner that I'd either have to purchase or visit the dealer?

Thanks

There are several scanners available for < $250. It's a must have tool for all modern engines and can pay for itself with one use. Search and you'll find several that people use.

Idle control valve should not cause those codes, but if you have not done so, remove it and clean it and the throttlebody.

I saw the Durametric scanner for just under $300 which is Porsche specific. What would you recommend for a more reasonable price? I've got more time than money right now as I'm in the off season of a seasonal business.

I removed the air filter housing a month or so ago, inspected the filter, hoses, clamps and related parts. The throttle body with less than 12k miles still looked new. I guess I could check again.

Also if an injector was leaking it would have to be more than one or at least one on each bank to cause both codes, correct? Rather unlikely on a 12k mile motor? I think so, but I'm not an expert.

I don;t know what the best priced one is. I have a custom one that is no longer made. http://www.autoenginuity.com/ is a good one too. You are correct about the leaky injectors. It would take at least one on each bank. Because it appears that both banks are running rich, it would likely be a common problem that effects both banks. Fuel pressure too high; blocked intake after MAF; bad gas; bad MAF signal or and open EVAP valve. Bad plugs could also cause the condition but I assume they are new with the engine.

Do you have your old MAF?

[nick49]

I can rule out bad gas, as I've had the codes and CEL for several tank fulls. I can rule out the blocked intake too.

I do have the old MAF. I also have the same MAF in my wife's Boxster that is good.

How do I check for a open EVAP valve?

The cars runs better with the new MAF than with the old one, noticeably so, I'm pretty in touch with this as I've jetted roadracing motorcycles for optimum performance for years.

I've had an ever so slight off idle stumble a few times recently that may be indicitive of something related. Again it's not regular and something I can't repete. I don't drive the car often in the winter as I live near the mountains and we've had snow for 6 weeks. So I'm driving it once a week and then for only 20 or so miles.

Thanks

[1999Porsche911]

I can rule out bad gas, as I've had the codes and CEL for several tank fulls. I can rule out the blocked intake too.

I do have the old MAF. I also have the same MAF in my wife's Boxster that is good.

How do I check for a open EVAP valve?

The cars runs better with the new MAF than with the old one, noticeably so, I'm pretty in touch with this as I've jetted roadracing motorcycles for optimum performance for years.

I've had an ever so slight off idle stumble a few times recently that may be indicitive of something related. Again it's not regular and something I can't repete. I don't drive the car often in the winter as I live near the mountains and we've had snow for 6 weeks. So I'm driving it once a week and then for only 20 or so miles.

Thanks

Have you cleaned the idle control valve?

[hiteck]

I have the same codes on my 99 C2. heard it could be O2 sensors too.

[Loren]

I have the same codes on my 99 C2. heard it could be O2 sensors too.

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

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

This says the mixture is too rich for the DME to compensate for. Chances are there is a bad MAF or a leak in the air/oil separator.

Potential causes:

- Fuel pressure too high.

- Fuel injector leaking.

- EVAP canister purge valve open.

The problem is NOT your sensors - your sensors are telling you where the problem is.

[nick49]

Thanks for the reply.

I'm still trying to track down the source of my problem.

Have 2 1/2 year old motor w/under 12k miles, and less than 100 miles on a new MAF

my thoughts, unlikely leaking injectors on both banks,

Still could be too high fuel pressure or EVAP purge valve open.

Where is it and how do I check it?

[nick49]

A little more info since my last post.

I erased the codes, cleaned some light residue from the inside of the throttle body, inspected the intake from there outward, replaced the air filter which was pretty clean originally.

The CEL came back on in less than 50 miles with the same 2 codes, nothing more.

I'm now noticeing more than ever, that when sitting a red light idling for a short time and starting out, the car will hesitate, buck and stumble and nearly die, then run fine.

It's loading up and will happen just off idle and sometimes just below 2000 RPM. I even filled the tank with fresh gas as I was about a quatrer full. Didn't make a difference. I added some heet to the tank thinking maybe had a condensation problem and haven't tried it since.

Something is causing it to run too rich at idle or very slightly above. Any ideas on the off idle stumble?

[JeTexas]

Just a guess, but one of your spark plugs might not be firing. Check your coils.

[twcjcarrera]

A little more info since my last post.

I erased the codes, cleaned some light residue from the inside of the throttle body, inspected the intake from there outward, replaced the air filter which was pretty clean originally.

The CEL came back on in less than 50 miles with the same 2 codes, nothing more.

I'm now noticeing more than ever, that when sitting a red light idling for a short time and starting out, the car will hesitate, buck and stumble and nearly die, then run fine.

It's loading up and will happen just off idle and sometimes just below 2000 RPM. I even filled the tank with fresh gas as I was about a quatrer full. Didn't make a difference. I added some heet to the tank thinking maybe had a condensation problem and haven't tried it since.

Something is causing it to run too rich at idle or very slightly above. Any ideas on the off idle stumble?

Nick49 - Did you ever resolve this? If so, what did you find?