vipclk320

Hello everyone, I have a 2009 997.2 C2S PDK. I've had a check engine light which I belive are related to to bad O2 sensors. We cleared the codes and reset the check engine light and all of a sudden the car would start but wouldn't hold idle and would die. Tried the 30 second throttle body position adaptation and no luck. Basically undriveable as it would die without having your foot on the gas. So I left the car there at the shop and went back the day after and the car was idling fine without doing anything to it. My mechanic said his PWIS is bad MAF but my MAF was less than 4 months old and a genuine Bosch purchased from autohausaz. So I said ok I'll get a new one and replace it again. I drove the car and everything was fine except once in a while when I came to a stop and idle dropped it would die but it only happened 3 times in 3 weeks. So I bought a new MAF replaced it and it did the same thing today when I drove it it died once at a a red light as I slammed on my break because a car cut infront of me. So I drove to the mechanic and had him replace all 4 of my O2 sensors with genuine Bosch ones from autohausaz. And we changed it and the car was driving just fine no problems at all. He asked me if i want the check engine light shutoff and since i was in a hurry and have an OBD2 plug I said no I'll do it. So I arrived to my destination and when I came back out I reset the check engine light via bluetooth OBD2 and my phone and did turned the ignition on for 1 minute and then started the car and no idle! It wouldn't stay on. So I tried the left foot on brake right on gas to keep idle behind lights and limped it home with about 10 shutoffs OB the way home as my foot kept slipping so I couldn't keep the rev high without annoying other drivers. On the way every patch of open road I got I floored it in Hope's of relearn but no go. I stopped on the way and raved it a couple of times and it started holding idle and I sat there letting it idle for 25 minutes, then I shut it off to see if it's fixed and same issues again. So I just drove/limped it home and parked it. Any idea as to what I'm doing wrong. This happens when i reset the check engine light. It happened a few times last year but it would just rough idle for a few minutes and it was good to go. But the last two times it just doesnt learn and last time it randomly fixed itself but then again I did have a few times that it died when I came to a sudden stop and RPM dropped fast. Sorry for the long novel but any help.is greatly appreciated.

Thank you in advance

systech

Might be worth checking the throttle body for crud ..or perhaps the associated throttle body control / actuator

vipclk320

Its clean and responsive, the problem is some how related to the check engine test. But cant figure out what. The car ran perfectly fine for 40 miles before check engine light reset.

Petza914

When you reset error codes, you also reset the DME fuel trims. It's best to do this with the car running and you'll hear it misfire and rough idle for a few seconds, but then it usually smooths out. If you clear the codes with the car off and the adaptations you need are fairly large, you can run into a situation where the car won't start. But in your case, you had it running again, so it should have relearned.

I would unplug the MAF sensor, forcing it to limp mode where it will use mid-range values, which should make it run, then with the engine still running, plug the MAF back in and with it still running do a clear on the engine fault codes. Once you've cleared the codes, with it still running, go for a drive and see if that works.

voiceprint1

Where are you taking the car in Los Angeles? That could make a big difference in diagnosis.

Greyghost230

Subscribed. This is a head scratcher. It sounds similar to a BMW problem I had with Air Flow sensor.

vipclk320

Thank you very much for the suggestion, I tried unplugging the MAF and it wouldn't even start.

swingwing

Have you ruled out fuel delivery problem? This engine (9A1) has direct injection, so way higher pressure at the injectors, 580-1740 psi (40 to 120 bar). There is a fuel low-pressure system (tank to HP pump) and engine driven HP fuel pump. Car will run in limp mode on the low pressure system. I have a nice Service Information/2009 Technik Introduction book from Porsche that came with purchase of my car. It details a lot of information about the 997.2 cars. From section on the new engine:

"The most important technical components of the direct fuel injection system are:
* The fuel low-pressure system
* The fuel high-pressure system
* The fuel high-pressure pump with flow control valve
* The fuel high-pressure line and the fuel distribution pipes to banks 1 and 2
* The fuel pressure sensor
* The fuel injectors (high-pressure fuel injectors)"

Hope this helps.

vipclk320

Update, I left the car over night and I just went down and started it and first crank it started right up and idled rough for about 20 seconds and back to normal as if nothing happened. Revved it a couple of times to see if it does once rpm drops fast and it stayed on and normal idle. Shut it off and did the same thing 20 minutes later and everything is good as if the problem was never there. This is super strange. Once check engine light comes on and I reset I guess I have to leave it over night. Lol

larrysb

One of the things to keep in mind is when the code says, "xyz sensor" it actually means that the computer thinks the signal from "xyz sensor" is invalid. That could be that the sensor is bad, but it also frequently means the connection between the sensor and the computer has gone wonky. Could be rat chewed wire, or some insulation that is chafed through, or a loose terminal, spot of corrosion, or the computer's input circuit is bad, or sometimes, it can mean unrelated things, like the battery voltage is down.

swingwing

How many miles on this car, and how old is the battery? Could be that a weak battery may be a contributor.

vipclk320

Just hit 100K and put a brand new battery in 2 weeks ago. I'm 100% sure this has something to do with the adaptation, I went down again this morning and the car runs and idles just fine,no issues what so ever. But I dont want to just let it go I want to get to the bottom of it to see if I'm doing something wrong when I reset the check engine light or if the adaptation process is different.

vipclk320

just wanted to update everyone. I hate when these threads are started and once the issue is solved the starter never updates the final results. Haha
So after two weeks of diagnoses with the factory computer and monitoring all the values we couldn't find anything out of ordinary but car kept having the same issue. So we removed the throttle body and ga e it a super deep and good cleaning, installed it back on and BOOM!!!! Car runs, idles and everything just fine! Also after resetting the check engine light it takes 2 minutes to adjust the idle and runs fine as all 911s do. So problem solved. Solution= clean that throttle body!
Thank you everyone for your suggestions and inputs, it helped rule out many possible issues.

DC911S

Yes, they really get junked up with black soot on the inside of the plenum input. Some people take a rag to it and leave it on, I removed mine and used CRC TB cleaner to really give it a good scrubbing. Don't know why its not mandated on the Porsche maintenance schedule. I think every 30K miles or so it needs to be done.

vipclk320

SOLD!