Cleared CEL now car runs poorly

[an86carrera]

Someone cleared CEL (there were 4 code don't know what they were) CEL had been on for a while and ran great. Now the car has reduced power until I reach 4500 -5000 rpm then normal. Problem is way worse until it warms up. I have driven the car about 50 miles since with no improvement and no CEL.

Any ideas? I know the codes should have been read but... :oops:

Thanks

Len

[Izzy]

You can probably extract and read codes, even though there is no CEL. If you don't have access to an OBDII reader, autoparts stores like Autozone will let you borrow theirs and use in the parking lot. Write down the codes.

What year and type of car?

[an86carrera]

OK car is 99 C4 here is a pic

Problem had an amazing recovery on way home tonight. No codes. Engine runs fine now :jump:

Now to the real issue. Everytime I reach 4500rpms the car will turn on the PSM OFF light and the ABS light on. PSM and ABS still work, but I can't turn off PSM at this point.

After a shutdown and restart the lights are back off only to turn on again as soon as I reach 4500rpms in 2nd or higher gear. This has gone on since July during a 1/4 mile run (13.8 sec by the way) Car has 100k miles original engine (no RMS) :)

Now that the car is 'back' any ideas on the problem now?

Thanks

Edited November 10, 2006 by an86carrera

[ianwallwork]

Problem had an amazing recovery on way home tonight. No codes. Engine runs fine now :jump:

Now to the real issue. Everytime I reach 4500rpms the car will turn on the PSM OFF light and the ABS light on. PSM and ABS still work, but I can't turn off PSM at this point.

After a shutdown and restart the lights are back off only to turn on again as soon as I reach 4500rpms in 2nd or higher gear. This has gone on since July during a 1/4 mile run (13.8 sec by the way) Car has 100k miles original engine (no RMS) :)

Now that the car is 'back' any ideas on the problem now?

Thanks

I think you have a MAF that's close to failing.

What I think is happening is this: when your CEL light was on, your MAF was not functioning properly and the car was running on the in-built pre-determined fuel map it uses if there is a MAF fault (If you completely disconnect the MAF you can still drive the car apparently normally because this map exists).

When the codes were cleared, your MAF was brought back into play. If I'm right and its calibration is wrong, it was causing your engine to be fuelled wrongly and you noticed this as a drop in performance. When the CEL came back on the MAF was disabled again as the DME saw it as faulty. The engine reverted to running on the pre-determined map and you got back the missing power.

Another possibility is failed lambda sensor(s) in the exhaust. The DME uses the feedback from these sensors to continuously correct the mixture at part throttle and also uses the correction information gained over time to calibrate the MAF sensor.

New lambdas and/or new MAF should have the car running like new.

Ian

[an86carrera]

Ian

I have yet to get another CEL just PSM OFF and ABS lights.

Thanks

[ianwallwork]

Ian

I have yet to get another CEL just PSM OFF and ABS lights.

Thanks

That is often indicative of MAF failure. I think your best bet is to get the codes read by your dealer or a good independent. They will then be able to investigate further and correctly diagnose the problem. Both the MAF and lambdas tend to have a relatively short life on 3.4-litre cars.

[an86carrera]

I don't like dealers much. I am one to fix my own. A good computerized ODB II software will give me the levels at the sensors that indicate these problems, right?

Suggestions? There is one reccomended here, any better?

Thanks,

[Loren]

http://www.renntech.org/reviewpost/showpro...t=17&cat=31

[an86carrera]

Well the car is still low on power but this morning the CEL came back on. With the CEL on a standard code reader gave me 1128 and 1130.

The OBD-2 software is at home waiting for me so I will have more info after I get that up and running. Anything I should do with it to help with the diagnosis?

Thanks

[Loren]

P1128 Oxygen sensing adaptation, idle range, bank 1

P1130 Oxygen sensing adaptation, idle range, bank 2

This means that your car is running too lean - the DME can not make the mixture rich enough to compensate for the lean condition.

You should check your MAF (TRA and FRA) and look for other air leaks like a torn oil filler hose, or oil seperator.

[Izzy]

Len,

I think I read your car has 100K miles, then I would change the O2 sensors and MAF. If they haven't been change at least once before, they are probably way past their life, due for late retirement. Mine lasted about 60K miles, same codes.

[an86carrera]

The Maf was changed at 90k service by Porsche. Going to check service records for O2s.

Got OBD-2 cable last night tried to hook up no luck. Called OBD-2 tech and could not resolve he is sending new cable today. Nice people.

Last time I cleaned MAF I did not remove it from the filter housing. So I bought the T20 security torq tool and removed it last night and realized that I missed cleaning the wire section and only cleaned the plate. This must have really confused the system:o)

So... the car is back to way it was. It is running nicely now.

But...I still get the PSM and ABS lights on the first time I pas 4700 rpm in any gear but first???? Lights stay on until I shut the car off. Restart car and rev past 4700 and there back on everytime with no obvious effect on running condition.It has been doing this since the dragstrip event..oops.

Will get back to this when new cable gets here this morning.

Thanks for the help.

[1999Porsche911]

The Maf was changed at 90k service by Porsche. Going to check service records for O2s.

Got OBD-2 cable last night tried to hook up no luck. Called OBD-2 tech and could not resolve he is sending new cable today. Nice people.

Last time I cleaned MAF I did not remove it from the filter housing. So I bought the T20 security torq tool and removed it last night and realized that I missed cleaning the wire section and only cleaned the plate. This must have really confused the system:o)

So... the car is back to way it was. It is running nicely now.

But...I still get the PSM and ABS lights on the first time I pas 4700 rpm in any gear but first???? Lights stay on until I shut the car off. Restart car and rev past 4700 and there back on everytime with no obvious effect on running condition.It has been doing this since the dragstrip event..oops.

Will get back to this when new cable gets here this morning.

Thanks for the help.

As mentioned above, check for leaks in the intake system. including throttlebody, oil cap, etc. When you get your scanner working, take a look at the O2 sensor readings at idle and if the system has the ability, log them from idle up to 6000 rpm while driving at half throttle. Are you running the stock exhaust?

If you want to check something in the meantime, remove air cleaner cover and put a piece of cardboard over approximately 1/3 of the air filter to reduce air to the engine. Reset codes and take it for a drive. Do the lights come back on again?

Edited November 16, 2006 by 1999Porsche911

[an86carrera]

Cable came in, it is the Tricom model and still having problems connecting with it, had the ISO-iTran model before. Will be talking to tech service for OBD-2.com again tonight.

[Loren]

Hmm... I've been using the ISO version for years.

Does it not connect?

[an86carrera]

I could not get the iso to connect, I am using the DB9 to USB adapter though.

Can I get any ABS info from this system?

Thanks

[Loren]

Hmm... I use the DB9 direct. I have not tried his USB cable.

No, there is no ABS info (other than Pcode faults) unless you manually enter the hex code queries - which I have not tried.

[an86carrera]

Reason I'm interested in the ABS codes is to do with my ABS an PSM lights coming on at 4700rpm in 2nd and 3rd maybe more gears. I have no codes now and still get the other light every trip cycle.

Do you like the other P-car specialized system better than this one?

Thanks

[Loren]

I think they both have their uses and a PST2 or PIWIS are a significant investment ($2000 to $18,000).

I wonder if you have a bad MAF connector or a pinched wire.

[1999Porsche911]

I could not get the iso to connect, I am using the DB9 to USB adapter though.

Can I get any ABS info from this system?

Sounds like the protocol of the USB port on yor computer. Check with tech as USB ports can be a pain to setup with proper emulation. I use just the opposite connection. I go from USB to serial cable using an adapter. Even finding an adapter to work properly was a pain in the *** and took 3 -4 purchases until I found the right one. Have you tried their serial cable?

Edited November 17, 2006 by 1999Porsche911

[an86carrera]

I did buy thier Serial to USB hardware and software as I have no where plug in a serial. And it worked on the Tricom cable.

[an86carrera]

O2 sensor voltages are not just cycling high / low as I think they should but holding high for a while some times and sometimes holding low. Other times they cycle high / low regularly.

Maf sensor is running about 4.5 at 700 rpm idle and 5.5 at 800 rpm idle.

Maf seems correct, o2s seem bad, my guess.

Any suggestions?

Thanks

[1999Porsche911]

O2 sensor voltages are not just cycling high / low as I think they should but holding high for a while some times and sometimes holding low. Other times they cycle high / low regularly.

Maf sensor is running about 4.5 at 700 rpm idle and 5.5 at 800 rpm idle.

Maf seems correct, o2s seem bad, my guess.

Any suggestions?

Thanks

Make sure that you are looking at the BEFORE CAT O2 sensors and not the after cats. They should be cycling high/low once the car has gone cclosed loop. You after cat sensors will be more steady, either high, low or anywhere in between.

Edited November 21, 2006 by 1999Porsche911