Check Engine Light, 1999 996

[doksoori]

I have a 1999 C2.

About 70 miles after changing the oil in my car with a mix of 5-30/0-40 Mobil 1, my check engine light came on. After I changed the oil, I had some idling issues as well. When idling, the car will go through a few periods of revving (always below 1K), and then it will eventually settle down and stay idle at a specific RPM. (This usually takes about 3-4 cycles before it settles down.) Same is true of my oil pressure gauge -- it moves around slightly when idling instead of cycling like my rpms. Thes problems went away during warmer days.

Right after changing the oil in my car, the car came up clean but it had a lot of problems idling... worse than it is now. After some driving, the hard idling went went away -- now I am left with the "cycling" that I describe above.

I have check the oil level and the oil cap (it is on tight).

I *think* it is not the MAF as I replaced that recently (few K ago).

As someone suggested, I went to Autozone, rented a OBDII sensor, and I got the following two codes:

P1124

Manufacture <something> Fuel Air Metering

P1126

Manufacture <something> Fuel Air Metering

(The same name for two codes.) Is this a problem with my mass air flow meter *again*?

Any help would be greatly appreciated.

Thanks!

-hjk

[1999Porsche911]

First of all, your problem has nothing to do with the type of oil you used (which in my optinion is wrong) or the level of oil or anything else with the slipperly liquid. The codes indicate that your engine is running lean. Either you are getting too little fuel or too much air. This can be caused by several things, but I would look at the obvious first. Make sure the O'ring on the oil filler cap is in good shape and that the cap is on tightly. Check for any leaks in the intake system (hoses, etc.) Also, add a bottle of injector cleaner to your fuel tank.

I would check the vacuum hoses and intake while the engine is running by carefully examining each hose and follwing it to each of it's ends, where possible, to make sure they are secure and free of cracks. You will probably hear a change in engine idle when you find the bad or disconnected hose. Assuming that the MAF is properly connected and cleaned, you will probably find the fix with the hoses.

Let us know as there are a few more things you can check.

Edited December 3, 2005 by 1999Porsche911

[doksoori]

Interesting...

I went through the engine, checked all the pipes and yet again retightened the oil cap. After driving around a little bit, the check engine light went out. Woohoo! The engine runs very smoothing as well. So I plugged in the OBD sensor one more time, but the codes that I reported earlier were still reported... odd since the CEL was no longer appearing. Does the porsche computer store the codes for a period of time even though the problem no longer exist?

I then reset everything by disconnecting my battery... after which, the car ran fine and the CEL stayed off.

-hjk

[1999Porsche911]

Interesting...

I went through the engine, checked all the pipes and yet again retightened the oil cap. After driving around a little bit, the check engine light went out. Woohoo! The engine runs very smoothing as well. So I plugged in the OBD sensor one more time, but the codes that I reported earlier were still reported... odd since the CEL was no longer appearing. Does the porsche computer store the codes for a period of time even though the problem no longer exist?

I then reset everything by disconnecting my battery... after which, the car ran fine and the CEL stayed off.

-hjk

When there is an problem with an monitored sensor, the computer will first record it as a "pending DTC". If it occurs again within a specific time, or remains a problem, the computer will then report it as a full CEL by activating the light. Some sensors will ocassionally have a hicup and can cause a pending DTC, but it won't happen again so no CEL is reported.

Glad it looks like it worked out for you.

[doksoori]

Again, thanks for your help! Hopefully, the CEL won't come on again.