yet another P1123 newbie thread

[JasonStern]

Drove home and CEL came on. Attached my Durametric. Error code is P1123. No other error codes. Car is stock with 20k miles. No recent known problems. I did have a non-start problem before:

http://www.renntech.org/forums/topic/43615-changed-oil-installed-997-shifter-now-car-wont-start/

...but after replacing the fuel filter, I haven't seen any symptoms in five months.

• Idle is at 680 RPM.

• Air Mass reading is 15-16 kg/h at idle and 50 kg/h at 2500RPM with no load.

• Oxygen sensing reading for cylinders 1-3 is 1.01 to 1.05 and for cylinders 4-6 s 0.99 to 1.02.

• O2 sensors read between 0.4V (lean) to 0.78v at idle and 2500RPM with no load.

Due to wife and nagging woman problems, I won't have time to dig into the car until this weekend. Checking the EVAP canister purge valve is on the top of my "to do" list. So I do apologize for posting without doing as much due diligence as possible, but, again, time concerns. Some guidance up front could easily prevent me from unnecessarily replacing moderately expensive parts.

Due to the lack of other CEL codes, the fact the car is running rich and I don't plan on driving it hard, and the code being a non-serious error, I cleared the error code and will drive it the rest of the week to see if the error retriggers.

So, my initial questions for the masterminds here:

• In Durametric, what is "oxygen sensing reading"? My best guess is that it is the flow rate injector compensation, but if that is the case, the value was changing constantly. Does that 0 to 0.03 discrepancy noticed between cylinder banks provide any useful information to further diagnose the cause?
• The MAF sensor readings look within spec, and since the MAF affects both cylinder banks, it seems unlikely to be the culprit. But, the sensor is 14 years old, countered by it only having 20k miles. From what I have read, the MAF sensor seems to take the blame for a lot of P1123 issues. But that could be misdiagnosed, especially if the issue is not easily reproducible.
• The O2 sensor values seem right, but I'm basing that on other vehicles, and the car wasn't under load. Do those values tip off any red flags?
• Are there any other metrics I can pull from the Durametric that might reduce the number of potential areas to investigate?

Thank you!

Edited July 17, 2013 by JasonStern

[Ahsai]

This is for boxsters but the principles should also apply to 996's

http://www.pelicanparts.com/techarticles/Boxster_Tech/19-FUEL-02_Sensor/OBD-II-scan.pdf

It calls for checking fuel pressure too high and leaking injectors.

When you said O2 sensor reading 0.4 to 0.8V, was that from the pre-cat sensor or post-cat sensor? Which bank? It will help if you can plot the pre-cat O2 readings of both banks together to compare the two during idle no load and fully warmed up. That way, you can see if your problem exists only on bank 1, which the code complains about. A fuel pressure problem should affect both banks.

Edited July 17, 2013 by Ahsai

[JFP in PA]

Drove home and CEL came on. Attached my Durametric. Error code is P1123. No other error codes. Car is stock with 20k miles. No recent known problems. I did have a non-start problem before:

http://www.renntech.org/forums/topic/43615-changed-oil-installed-997-shifter-now-car-wont-start/

...but after replacing the fuel filter, I haven't seen any symptoms in five months.

• Idle is at 680 RPM.

• Air Mass reading is 15-16 kg/h at idle and 50 kg/h at 2500RPM with no load.

• Oxygen sensing reading for cylinders 1-3 is 1.01 to 1.05 and for cylinders 4-6 s 0.99 to 1.02.

• O2 sensors read between 0.4V (lean) to 0.78v at idle and 2500RPM with no load.

Due to wife and nagging woman problems, I won't have time to dig into the car until this weekend. Checking the EVAP canister purge valve is on the top of my "to do" list. So I do apologize for posting without doing as much due diligence as possible, but, again, time concerns. Some guidance up front could easily prevent me from unnecessarily replacing moderately expensive parts.

Due to the lack of other CEL codes, the fact the car is running rich and I don't plan on driving it hard, and the code being a non-serious error, I cleared the error code and will drive it the rest of the week to see if the error retriggers.

So, my initial questions for the masterminds here:

• In Durametric, what is "oxygen sensing reading"? My best guess is that it is the flow rate injector compensation, but if that is the case, the value was changing constantly. Does that 0 to 0.03 discrepancy noticed between cylinder banks provide any useful information to further diagnose the cause?
• The MAF sensor readings look within spec, and since the MAF affects both cylinder banks, it seems unlikely to be the culprit. But, the sensor is 14 years old, countered by it only having 20k miles. From what I have read, the MAF sensor seems to take the blame for a lot of P1123 issues. But that could be misdiagnosed, especially if the issue is not easily reproducible.
• The O2 sensor values seem right, but I'm basing that on other vehicles, and the car wasn't under load. Do those values tip off any red flags?
• Are there any other metrics I can pull from the Durametric that might reduce the number of potential areas to investigate?

Thank you!

The P1123 Code "Oxygen Sensing adaptation range 1 Cylinders 1-3) Lean limit" is referring to the fact that DME has reached its limit is trying to lean out that bank and the car is running too rich as the result. Usual two suspects are either high fuel pressure or a leaking injector(s) on that side. As you have not identified your year or model, in some cases is can also be a defect fuel pressure regulator on the injector fuel rail, depending upon the year, as some models do not have the external regulator. There is little probability of the MAF being involved in this issue.

Step number one should be to get a fuel pressure reading off the test port on the fuel rail, should be 55+/-3 PSIG engine off; 48+/-3 PSIG engine running. If it is an early car with an external fuel pressure regulator, pull the vacuum line off the regulator and read the vacuum on the line, should be around 15 inches of vacuum. Checking the individual injectors is a bit more difficult; for a DIY, probably the easiest approach is to pull all the plugs on that bank and check their color. If one or more are overly dark, those would be your suspect injectors.

[JasonStern]

First off, thank you for that PDF.

After clearing the fault code but not disconnecting the battery to make the ECU re-learn the fuel curves, I have driven 35 miles without the fault re-triggering.

When you said O2 sensor reading 0.4 to 0.8V, was that from the pre-cat sensor or post-cat sensor? Which bank? It will help if you can plot the pre-cat O2 readings of both banks together to compare the two during idle no load and fully warmed up. That way, you can see if your problem exists only on bank 1, which the code complains about. A fuel pressure problem should affect both banks.

The O2 sensor readings were for both pre- and post-catalytic converter. Attached is a screenshot of the O2 sensor readings from Durametric when warm. The low values seem to be lower today than yesterday. Getting cold numbers is a bit more difficult due to working in the morning, but I will try to provide those when I can.

Unless you mean "Oxygen sensing cylinders 1-3" and "Oxygen sensing cylinders 4-6", I am not seeing how to measure the O2 sensor voltage of a specific bank. And the oxygen sensing reading for cylinders 1-3 is 1.01 to 1.05 and for cylinders 4-6 s 0.99 to 1.02, which seems out of the sweet spot if that value does reflect an O2 sensor - unless maybe the value is scaled so that 1.0 is 14.7:1...?

• The P1123 Code "Oxygen Sensing adaptation range 1 Cylinders 1-3) Lean limit" is referring to the fact that DME has reached its limit is trying to lean out that bank and the car is running too rich as the result. Usual two suspects are either high fuel pressure or a leaking injector(s) on that side. As you have not identified your year or model, in some cases is can also be a defect fuel pressure regulator on the injector fuel rail, depending upon the year, as some models do not have the external regulator. There is little probability of the MAF being involved in this issue.
  Step number one should be to get a fuel pressure reading off the test port on the fuel rail, should be 55+/-3 PSIG engine off; 48+/-3 PSIG engine running. If it is an early car with an external fuel pressure regulator, pull the vacuum line off the regulator and read the vacuum on the line, should be around 15 inches of vacuum. Checking the individual injectors is a bit more difficult; for a DIY, probably the easiest approach is to pull all the plugs on that bank and check their color. If one or more are overly dark, those would be your suspect injectors.

Sorry about that. My car is a 1999 Carrera C2. It does have a fuel pressure regulator on the fuel injector rail. Looks like I need to order a fuel pressure and vacuum gauge.

Regarding the MAF, darn. I didn't think so. It's never the relatively cheap part that is easy to access...

So if it does turn out to be fuel injector related, what are the odds that sending the injectors to be professionally cleaned would fix them versus having to replace one or more injectors?

Thank you!

Edited July 18, 2013 by JasonStern

[binger]

Hi Jason,

The screenshot gives us one more piece of the puzzle. The upstream o2 sensors should be switching 200 mV to 850 mV. for a 14.7:1 fuel ratio. Your o2 sensors 0.4 mV to 0.74mV is giving a lean bis command to the ECU in turn adds more fuel. Do you know if you were in closed loop when you took the screen shot? the cat needs to be at least 600 F. to go in to closed loop. You really need more than just a fuel presser gauge and a vacuum pump and gauge to get to the root cause of the issue. You should also have scan tool that can show what the long term and short fuel trims are doing for a proper diagnosis.

If you get a MIL light again before you clear the codes I would get the freeze frame data as this will give a clearer picture of what was happening when the MIL was triggered. There are several issues that could be the cause. 1.fuel pressure 2.leaking injectors 3. vacuum leak.4. unmetered air just after the MAF or at the exhaust just before the o2 sensors. You might want to consider paying for a professional diagnosis then you can do the work to fix the issue to save some $$$.

Bing SokolskyDiagnostic Auto Lab

www.diagnosticautolab.com

[JFP in PA]

First off, thank you for that PDF.

After clearing the fault code but not disconnecting the battery to make the ECU re-learn the fuel curves, I have driven 35 miles without the fault re-triggering.

When you said O2 sensor reading 0.4 to 0.8V, was that from the pre-cat sensor or post-cat sensor? Which bank? It will help if you can plot the pre-cat O2 readings of both banks together to compare the two during idle no load and fully warmed up. That way, you can see if your problem exists only on bank 1, which the code complains about. A fuel pressure problem should affect both banks.

The O2 sensor readings were for both pre- and post-catalytic converter. Attached is a screenshot of the O2 sensor readings from Durametric when warm. The low values seem to be lower today than yesterday. Getting cold numbers is a bit more difficult due to working in the morning, but I will try to provide those when I can.

Unless you mean "Oxygen sensing cylinders 1-3" and "Oxygen sensing cylinders 4-6", I am not seeing how to measure the O2 sensor voltage of a specific bank. And the oxygen sensing reading for cylinders 1-3 is 1.01 to 1.05 and for cylinders 4-6 s 0.99 to 1.02, which seems out of the sweet spot if that value does reflect an O2 sensor - unless maybe the value is scaled so that 1.0 is 14.7:1...?

• The P1123 Code "Oxygen Sensing adaptation range 1 Cylinders 1-3) Lean limit" is referring to the fact that DME has reached its limit is trying to lean out that bank and the car is running too rich as the result. Usual two suspects are either high fuel pressure or a leaking injector(s) on that side. As you have not identified your year or model, in some cases is can also be a defect fuel pressure regulator on the injector fuel rail, depending upon the year, as some models do not have the external regulator. There is little probability of the MAF being involved in this issue.
  Step number one should be to get a fuel pressure reading off the test port on the fuel rail, should be 55+/-3 PSIG engine off; 48+/-3 PSIG engine running. If it is an early car with an external fuel pressure regulator, pull the vacuum line off the regulator and read the vacuum on the line, should be around 15 inches of vacuum. Checking the individual injectors is a bit more difficult; for a DIY, probably the easiest approach is to pull all the plugs on that bank and check their color. If one or more are overly dark, those would be your suspect injectors.

Sorry about that. My car is a 1999 Carrera C2. It does have a fuel pressure regulator on the fuel injector rail. Looks like I need to order a fuel pressure and vacuum gauge.

Regarding the MAF, darn. I didn't think so. It's never the relatively cheap part that is easy to access...

So if it does turn out to be fuel injector related, what are the odds that sending the injectors to be professionally cleaned would fix them versus having to replace one or more injectors?

Thank you!

Yes, the injectors can be refurbished, there are a lot of shops that do this, so look for one in your area.

[Ahsai]

Hi Jason,

... Your o2 sensors 0.4 mV to 0.74mV is giving a lean bis command to the ECU in turn adds more fuel. ...

Hi Bing,

Did you mean the opposite? 0.4V~0.74V indicates the sensor sees a RICH mixture so the DME will try to reduce fuel (i.e., fuel trim will be negative). Also consistent with the code, which complains that the DME needs to remove too much fuel to get the correct A/F ratio.

Jason,

Your attached O2 readings seems to be for bank 1 (red) and bank 2(blue) both pre-cat sensors. They look fine (good voltage range) albeit switching a little slower than I remember. Would be good to also log the same during cold start. Should take a couple of minutes if that to get smiilar swinging measurements since the O2 sensors are heated.

[binger]

I know it can be confusing how these systems work. It is the opposite of what we might think. The o2 sensor reads the gas just before the cat and sends a signal to the DME. If it has low voltage the DME sees that as the motor is too lean. The DME now commands the injectors to add more fuel by making pulse width longer. That's why your car is running rich. Hope this helps.

Bing

Diagnostic Auto Lab

[Ahsai]

I know it can be confusing how these systems work. It is the opposite of what we might think. The o2 sensor reads the gas just before the cat and sends a signal to the DME. If it has low voltage the DME sees that as the motor is too lean. The DME now commands the injectors to add more fuel by making pulse width longer. That's why your car is running rich. Hope this helps.

Bing

Diagnostic Auto Lab

Now I see what the problem is. Jason said he saw 0.4V-0.78V but your post said 0.4mV to 0.78mV....the units are different.

[JasonStern]

Again, a thank you to all providing your invaluable information.

The screenshot gives us one more piece of the puzzle. The upstream o2 sensors should be switching 200 mV to 850 mV. for a 14.7:1 fuel ratio. Your o2 sensors 0.4 mV to 0.74mV is giving a lean bis command to the ECU in turn adds more fuel. Do you know if you were in closed loop when you took the screen shot? the cat needs to be at least 600 F. to go in to closed loop. You really need more than just a fuel presser gauge and a vacuum pump and gauge to get to the root cause of the issue. You should also have scan tool that can show what the long term and short fuel trims are doing for a proper diagnosis.

The coolant was warm when I took the screen shot as I had just driven home. However, the car was off for a few minutes prior to the reading in order to grab my laptop and Durametric, so if there is some sort of temperature gauge on or near the catalytic converter, then I have no idea what the temperature was at the time of the reading. It is almost the weekend, so I will try to read up more on the Durametric and provide more information then.

While the fuel pressure gauge and vacuum gauge seem like they will only verify whether or not the problem is either the fuel pump, fuel pressure regulator, or a vacuum leak, it would still be nice to rule those out. Unfortunately, I had to order those online so it will be a few days before I can check them.

If you get a MIL light again before you clear the codes I would get the freeze frame data as this will give a clearer picture of what was happening when the MIL was triggered. There are several issues that could be the cause. 1.fuel pressure 2.leaking injectors 3. vacuum leak.4. unmetered air just after the MAF or at the exhaust just before the o2 sensors. You might want to consider paying for a professional diagnosis then you can do the work to fix the issue to save some $$$.

I will definitely consider taking it to a shop if the code re-triggers. However, so far I have just over 75 miles without the code re-triggering, and the car is showing no symptoms of any problems, so I'm cautiously optimistic the CEL occurring was just a hiccup due to the low octane, ethanol laced mixture they call gasoline in the western U.S. Not that such a thing would stop me from doing some simple checks to try to ensure a potential failure is not about to occur.

Your attached O2 readings seems to be for bank 1 (red) and bank 2(blue) both pre-cat sensors. They look fine (good voltage range) albeit switching a little slower than I remember. Would be good to also log the same during cold start. Should take a couple of minutes if that to get smiilar swinging measurements since the O2 sensors are heated.

That might be due to the Durametric has a time value in which it polls for updates, and I left it at the default value. I will try to read up more on it this weekend and hopefully provide additional information.

Attached are the cold reading values. As you said, at first nearly no voltage was read, but after about a minute, the values started oscillating.

Now I see what the problem is. Jason said he saw 0.4V-0.78V but your post said 0.4mV to 0.78mV....the units are different.

For clarification, I did see 0.4V-0.78V the first time (without a screenshot) and 0.05V to 0.75V the second time. See the screenshot in my previous post for the graph the Durametric tool generated.

[binger]

Hi Jason,

We are going to need more info so I can try to walk you through the steps to solve your issue. Please fill out the two work sheets and post the info. This weekend when you use your scan tool please check the following RPM, ECT, TPS, MAF, IAT, both upstream o2 sensors and downstream o2 sensors. The car needs to be at operating temp & closed loop, the motor should be ran up to 2000 RPMs. Please in post this info too. You will need a fuel pressure gauge a hand vacuum pump & vacuum gauge. FYI the only real way to test for vacuum leaks is with a smoke machine and that costs lots of $$$$.

Customer Concerns.pdf

Drivability Work sheet.pdf

Edited July 19, 2013 by binger

[JasonStern]

Hi Jason,

We are going to need more info so I can try to walk you through the steps to solve your issue. Please fill out the two work sheets and post the info. This weekend when you use your scan tool please check the following RPM, ECT, TPS, MAF, IAT, both upstream o2 sensors and downstream o2 sensors. The car needs to be at operating temp & closed loop, the motor should be ran up to 2000 RPMs. Please in post this info too. You will need a fuel pressure gauge a hand vacuum pump & vacuum gauge. FYI the only real way to test for vacuum leaks is with a smoke machine and that costs lots of $$$$.

The MIL came on again with the same P1123 code. I was driving home in ~100'F weather. I drove about 15 miles on the freeway, and then the light came on after roughly 30 seconds idling stopped at a traffic light from the freeway off-ramp. So the problem is recurring. I cannot seem to figure out how to get the freeze frame data from the Durametric tool. I e-mailed their technical support, so hopefully they can explain how, presuming Motronic 5.2.2 is supported - they worded it rather vaguely in the manual.

Attached are logs from almost all of the meters that the Durametric tool will let me log. Unless stated "cold", the readings were taken with the motor running at approximately 2,000 RPM. Do note that there is no TPS voltage reading. However, there is a throttle plate angle metric that varies between 0' with no throttle applied and 67' when the throttle is depressed. The IAT sensor measured accurate cold. However, I didn't do any additional testing beyond that. The Durametric does not have the ability to measure the individual O2 sensors, but the values that could be read are provided.

I am still waiting on the vacuum and fuel pressure gauges in the mail and will post the results once they arrive and I have time to measure the respective values.

Regarding those PDFs:

Rate of Occurrence: 120 miles

Time of day: Evening

Engine temperature: Normal

Outside temperature: Hot

Driving conditions: Idle

Gas Pedal: Released

Gear: Neutral

Occurs after: Driving

Road Conditions: Dry

Fuel: 91 octane with 10% ethanol :(

MIL: On

No Starting Faults

No idle issues

No performance issues

Same gas mileage

No pinging

No smells

No smoke

Above 80'F Ambient Temperature

No recent repairs

No modifications other than a 997 shifter

Thank you!

durametric.zip

Edited July 22, 2013 by JasonStern

[binger]

Hi Jason,

You said,

No idle issues

No performance issues?

So your 996 is running fine? it's not running rich? or your just getting the P1123 code? from the latest o2 upstream sensors PDF you posted the DME has no fuel control. the readings look worse that your first post. I did find a TSB on your car for o2sensors see this link below. Also the next time you test the down stream o2 sensors please change the values from Ohms to mV. Thank you in advance.

http://www.renntech.org/forums/index.php?app=downloads&module=display&section=download&do=confirm_download&id=165

[JasonStern]

Hi Jason,

You said,

No idle issues

No performance issues?

So your 996 is running fine? it's not running rich? or your just getting the P1123 code? from the latest o2 upstream sensors PDF you posted the DME has no fuel control. the readings look worse that your first post. I did find a TSB on your car for o2sensors see this link below. Also the next time you test the down stream o2 sensors please change the values from Ohms to mV. Thank you in advance.

http://www.renntech.org/forums/index.php?app=downloads&module=display&section=download&do=confirm_download&id=165

First off, no need to thank me. You are the one taking the time to help me out, and I appreciate that.

Regarding no idle issues, there are none that I know of. The car keeps a consistent idle at around 700 RPM. There is only minor deviance when running at idle or when shifting from load into neutral. But there definitely has not been any surges or stalls.

Regarding performance issues, there are none that I am aware of. The car is used as a daily driver when both I choose not to ride my motorcycles and when the roads permit, so as a result I usually shift at around 3,000 RPM. And in that non-track, speed limit enforced, public road setting, I have noticed nothing out of the ordinary. This makes me think that something is beginning to fail as opposed to something that has already failed.

Regarding running rich, it probably is. Probably not consistently, but when certain criteria - high ambient temperatures, car fully warmed up, engine at idle - I would presume so. I see no other reason as to why the CEL would trigger otherwise. From just a nearly baseless "sniff test", the car runs really rich when it starts, but once the O2 sensors heat up, it tends to lean itself out.

Regarding the O2 upstream sensors looking worse, alright. I'll donate to read the link you provided. :)

Regarding changing the downstream O2 sensors from ohms to volts, the Durametric does not appear to have the ability to do so. Remember - I only have access to a $287 aftermarket tool and not factory diagnostic tools.

[JFP in PA]

Hi Jason,

You said,

No idle issues

No performance issues?

So your 996 is running fine? it's not running rich? or your just getting the P1123 code? from the latest o2 upstream sensors PDF you posted the DME has no fuel control. the readings look worse that your first post. I did find a TSB on your car for o2sensors see this link below. Also the next time you test the down stream o2 sensors please change the values from Ohms to mV. Thank you in advance.

http://www.renntech.org/forums/index.php?app=downloads&module=display&section=download&do=confirm_download&id=165

First off, no need to thank me. You are the one taking the time to help me out, and I appreciate that.

Regarding no idle issues, there are none that I know of. The car keeps a consistent idle at around 700 RPM. There is only minor deviance when running at idle or when shifting from load into neutral. But there definitely has not been any surges or stalls.

Regarding performance issues, there are none that I am aware of. The car is used as a daily driver when both I choose not to ride my motorcycles and when the roads permit, so as a result I usually shift at around 3,000 RPM. And in that non-track, speed limit enforced, public road setting, I have noticed nothing out of the ordinary. This makes me think that something is beginning to fail as opposed to something that has already failed.

Regarding running rich, it probably is. Probably not consistently, but when certain criteria - high ambient temperatures, car fully warmed up, engine at idle - I would presume so. I see no other reason as to why the CEL would trigger otherwise. From just a nearly baseless "sniff test", the car runs really rich when it starts, but once the O2 sensors heat up, it tends to lean itself out.

Regarding the O2 upstream sensors looking worse, alright. I'll donate to read the link you provided. :)

Regarding changing the downstream O2 sensors from ohms to volts, the Durametric does not appear to have the ability to do so. Remember - I only have access to a $287 aftermarket tool and not factory diagnostic tools.

Durametric can read and graph O2 sensor voltages...........

[JasonStern]

Durametric can read and graph O2 sensor voltages...........

As far as I have been able to figure out, Durametric 6.3.1.7 can only read the "O2 sensor voltage ahead of cat. conv." and "O2 sensor voltage ahead of cat. c. bank 2" on Bosch ME5.3.2 equipped cars. There doesn't appear to be pre-cat/post-cat and cylinders 1-3/cylinders 4-6 options, of which values were requested. :(

Regarding that TSB binger posted, while the information isn't relevant yet, if further diagnosis indicates an O2 sensor failing, that information is very good to know. Thanks for that.

Edited July 23, 2013 by JasonStern

[Ahsai]

Jason,

You have already been posting precat O2 sensor readings for both banks (red=bank1=cyl 1-3, lue=bank2=cyl 4-6) so all you need is post-cat O2 sensor readings, which is not that critical in this case I think.

Your TRA is -0.24 (bank1) and -0.19 (bank2), which means at idle, the DME has to REMOVE 24% and 19% of fuel to keep the ideal A/F ratio.

Your FRA is +1.10 (bank1) and +1.08 (bank2), which means at load, the DME has to ADD 10% and 8% of fuel to keep the ideal A/F ratio.

So whatever you have seems to be affecting both banks. The readings seem to very close to "too little fuel at load" example #3 on page 8 here.

[Ahsai]

Your "O2 2k" graph is very strange that the sensors are swinging way too slowly. Was the reading taken at idle or other rpm? Also, what was the sampling rate? At idle, I expect swinging about once per second and at 2k rpm, the swinging should be even faster.

[JasonStern]

Jason,

You have already been posting precat O2 sensor readings for both banks (red=bank1=cyl 1-3, lue=bank2=cyl 4-6) so all you need is post-cat O2 sensor readings, which is not that critical in this case I think.

Your TRA is -0.24 (bank1) and -0.19 (bank2), which means at idle, the DME has to REMOVE 24% and 19% of fuel to keep the ideal A/F ratio.

Your FRA is +1.10 (bank1) and +1.08 (bank2), which means at load, the DME has to ADD 10% and 8% of fuel to keep the ideal A/F ratio.

So whatever you have seems to be affecting both banks. The readings seem to very close to "too little fuel at load" example #3 on page 8 here.

Thank you. This definitely seems relevant:

Reference TRA: -0.11

My TRA: -0.24

Reference TRA2: -0.12

My TRA2: -0.19

Reference FRA: 1.11

My FRA: 1.10

Reference FRA2: 1.12

My FRA2: 1.08

Too little fuel in area 2 (e.g. insufficient supply from pump). Affects all cylinders. The considerable enrichment in area 2 also has an effect on area 1.

My fuel pressure gauge and vacuum gauge arrived. Now I am just waiting on the fuel pressure adapter from Actron, which should arrive on Wednesday or Thursday.

Your "O2 2k" graph is very strange that the sensors are swinging way too slowly. Was the reading taken at idle or other rpm? Also, what was the sampling rate? At idle, I expect swinging about once per second and at 2k rpm, the swinging should be even faster.

The original readings were done either at idle or 2,500 RPM. Those did not have the refresh rate in Durametric maxed out. The readings in the zip file were done at 2,000 RPM with the Durametric refresh rate set to the max.

Regarding the freeze frame data, Durametric got back to me:

Thank you for contacting Durametric. Unfortunately, we do not yet support freeze frame viewing on the ME5.2.2 engine unit at this time. This data is available in conjunction with the fault code display within the program on all other 996 DME models. We will research if this is even possible on this unit, and if so, add it to the program in a future release. Please contact us if we can be of any further assistance.

So that is a bit disappointing.

Edited July 24, 2013 by JasonStern

[JasonStern]

Sorry for the delay, but I finally got a day off.

With the car stationary, the fuel pressure read 3.7 BAR, which is within the 3.8 +/- 0.2 BAR factory specs.

With the car at idle, the fuel pressure read 3.3 BAR, which is within the 3.3 +/- 0.2 BAR factory specs.

With the car at idle, the vacuum applied at the fuel pressure regulator was 0.9 BAR. This is well above the 0.4-0.6 BAR factor specs.

So:

1. The fuel pump appears to be functioning properly.

2. The engine was cold when the vacuum reading was taken. The PDF Ahsai linked to did not specify whether the engine should be warm or cold. Would this affect the vacuum applied to the fuel pressure regulator?

3. If engine operating temperature is not a factor, a low vacuum reading would indicate either a vacuum or intake leak. What would excessive vacuum pressure indicate?

Thank you!

[RFM]

A simple question, what about the condition of the OAS?

[JFP in PA]

Sorry for the delay, but I finally got a day off.

With the car stationary, the fuel pressure read 3.7 BAR, which is within the 3.8 +/- 0.2 BAR factory specs.

With the car at idle, the fuel pressure read 3.3 BAR, which is within the 3.3 +/- 0.2 BAR factory specs.

With the car at idle, the vacuum applied at the fuel pressure regulator was 0.9 BAR. This is well above the 0.4-0.6 BAR factor specs.

So:

1. The fuel pump appears to be functioning properly.

2. The engine was cold when the vacuum reading was taken. The PDF Ahsai linked to did not specify whether the engine should be warm or cold. Would this affect the vacuum applied to the fuel pressure regulator?

3. If engine operating temperature is not a factor, a low vacuum reading would indicate either a vacuum or intake leak. What would excessive vacuum pressure indicate?

Thank you!

The PDF states that the engine should be warmer than 62C. 0.9 Bar ( or about 26.6 inches of mercury) vacuum on the fuel pressure regulator seems a bit high, I would normally expect about 15 inches.

[Ahsai]

Question, does your vacuum gauge read 1bar absolute pressure (i.e., 1 bar = atmospheric pressure) when it's not connected to anything? If so, 0.9 bar reading means the vacuum is very weak that it's very close to the atmospheric pressure hence not providing much vacuum. That is different than saying 0.9bar of vacuum or 26.6 inHg, which btw I don't think our engine can ever pull even at idle fully warmed up.

Another point is the pdf is for Boxsters so the detail numbers may not be the same as 996's although I would imagine the pressure specs should be close. I could not find the 996 equivalent version.

[JasonStern]

A simple question, what about the condition of the OAS?

The car is a 99 and it appears to have the original air/oil separator, so I suppose it could be possible that the AOS is the culprit. But the car has no oil consumption, no smoke at start up, and a slight negative pressure with a rough idle when the cap is removed, so it seems like the problem is likely elsewhere.

The PDF states that the engine should be warmer than 62C.

Yeah. I misread the PDF originally as conditions necessary to trigger the CEL as they were similar. :blush:

0.9 Bar ( or about 26.6 inches of mercury) vacuum on the fuel pressure regulator seems a bit high, I would normally expect about 15 inches.

The idle is higher than the diagnostic condition states when the the engine is cold, so that might have affected the reading. I'm surprised if it would be by that much, though. When I get some time, I will try to re-read the values with the engine hand-burningly hot. Presuming the vacuum is high, do you have any ideas of what might be causing that?

Question, does your vacuum gauge read 1bar absolute pressure (i.e., 1 bar = atmospheric pressure) when it's not connected to anything? If so, 0.9 bar reading means the vacuum is very weak that it's very close to the atmospheric pressure hence not providing much vacuum. That is different than saying 0.9bar of vacuum or 26.6 inHg, which btw I don't think our engine can ever pull even at idle fully warmed up.Another point is the pdf is for Boxsters so the detail numbers may not be the same as 996's although I would imagine the pressure specs should be close. I could not find the 996 equivalent version.

The gauge is calibrated so that zero PSI when not connected. When I redo the vacuum measurement with the engine warm, I will provide a picture of the measurement for clarification.

Thank you all!

[Ahsai]

In that case, I think your 0.9 bar ( negative 0.9 bar strictly speaking since 0 bar gauge reading = atmospheric pressure) is highly suspicious since it's close to complete vacuum. Our engines just cannot produce that much vacuum at idle. You should read about -0.58 bar (17 inHg) if you are at sea level. http://www.renntech.org/forums/topic/40898-need-help-with-intake-vacuum-gauge-reading-from-more-cars/#entry241744