A few things to start things off:
1. My car has 34k on it
2. I have the stock air filter
3. My ECU is bone stock (not chipped)
4. I have an aftermarket exhaust (turbo exhuast v8.0)
5. I have Bailey diverter valves

Over the past few months, I have been battling a CEL light that comes ONLY under idle. The light is always P0175 (System too rich bank 2) and sometimes P0172 (System too rich bank 1) if I let it idle long enough. Keep in mind, though, this happens ONLY under idle.

My o2 sensors seem to be working correctly (I never received a CEL relating to them) and I *believe* that all hoses are properly attached. P0175 and P0172 were the only CELs that I received. I would reset them with my datalogger and continue on. My symptoms included low-speed hesitation (1st gear), highly negative short term fuel trim values under idle, and positive l(perhaps +3 to +7) long term fuel trims after a spirited drive. I even went as far as to clean my MAF in order to narrow down my problems. After the initial cleaning, I didn't receive another CEL for about 2 months and the car seemed to run well. However, my problems eventually came back and the CEL was staring me in the face yet again.

I decided to order the 986 MAF knowing that I might need a DME flash in order to account for the new values that my MAF would read/need. It was my hope that I could get this 986 MAF to work in my car being that it is supposed to be more "beefy" and less prone to fail.

Let me just say that with my setup (stock ECU, stock turbos, stock intake, after market exhaust), the 986 MAF is not the answer. Will it work for you if you have a lot of mods (ECU, new turbos, fuel pressure regulator, etc.)? Probably so. That is up to you if you want to try. Upon switching it into my car, I immediately experienced a higher idle and hesitation under WOT. I drove a few cycles and the symptoms did not clear up. I felt pretty confident that this was not going to work.

So, I gave our good buddies at Imagine Auto a call and bought a 996TT MAF from Stephen. I've only had the MAF in for a few cycles, but the car seems to be running very well. I will need to do more long-term testing in order to make sure that the MAF was the cause, however. I have noticed that my rear downstream o2 sensor on bank 2 (the same bank that throws the first CEL - P0175) seems to be a "little" lazy, but nothing of too much concern. The last time that I had an o2 sensor go out (@ 10k miles), I received a different CEL. Besides, I am getting a CEL from both banks at idle, so having two o2 sensors go out at the same time would be a long-shot (but possible I guess).

I'll report back on my MAF situation in a few days, but I am hoping that this fixed it. If the CEL comes on yet again, I will be forced to take my car into Porsche for a diagnostics test. I'll be sure to update my progress.

 

Ruiner your posts and info are really helpfull man, looking forward to hearing more of your impressions, i also think cleaning did the job for me for a good few weeks, and the spark plugs were my hesitation under full throttle problems, but i think im just going to replace my MAF for the hell of it!

 

I am informed by Stephen and Todd that the 986 MAF only works well on higher HP cars. I had a 986 MAF for a while and it worked fine, although I recently blew it as well.

Craig

 

Even then on some of the kits it does not work well.

 

I drove it for about 20 minutes this morning. Normal, stop and go traffic with one or two 2nd and 3rd gear punches. I really mixed it up. The car felt very good and I couldn't detect any hesitation in slow, 1st gear rolls (one of the previous symptoms).

I checked my fuel trims after I got done driving and noticed that both banks of my LTFTs were -1 while my STFTs were cycling from -3 to +5 (all at idle). I am used to having LTFTs in the +3 to +5 area. So far, so good. I'll report back after I run a few more hard and varied cycles.

Thank you so much for your help, Stephen. Imagine Auto really came through with sound advice and product delivery.

 

Hmm interesting once again, Ruiner we've gone through this, but im still finding a hesitation going into first gear and the slow acceleration, feels like a dead spot and then starts climbing.. I guess i should just replace my MAF sensor with a new one correct? I also notice it becomes rough or starts doing it with the less gas i have in the car, shifting is also more rough with like a 1/4 tank oppsed to 1/2 tank, really weird

 

You might need to switch it out. However, datalogging it would be even better.

I just looked at my data logger after driving around during lunch:

New MAF @ idle...

LTFTs:
bank 1: -2
bank 2: -3

STFTs:
bank 1: -3 to +2
bank 2: 0 to +4

My previous results with the "old" MAF @ idle:

LTFTs:
bank 1: +3
bank 2: +5

STFTs:
bank 1: -15 to -18
bank 2: -17 to -21

 

So if i data log would you tell me if i need a new MAF sensor, also how should i go about data logging

 

A datalogger is just a tool that will help you see the real-time results for your car's operation. It plugs into your ECU via the OBDII port and recods what your ECU sees (rpm, fuel trims, load, throttle position, o2 sensor values, speed, etc).

As for getting one, perhaps a friend has one? I bought a datalogger many years ago as I used it to tune my previous turbo'd car. All you need is an OBDII datalogger. Borrow it from a friend if you can. You can buy one of course, but they typically range anywhere from $150-300 for the software/cable. You can get softare that interfaces with your laptop/palm pilot or stand-alone units.

 

Well im pretty sure i can use mys hops, but it has to be connected while driving, or what tests should i do with it to tell if its the MAF sensor??

Also iw onder if they have somethign to hook up with the Treo since its palm based

 

You can datalog while driving or at idle. I checked my MAF at idle both times as a bad MAF typically shows issues at idle (which is when my CEL lights were tripped). Driving and watching the values is of also of great benefit as well.

The current list... You can always email Mike and ask him:

http://www.pocketlogger.com/index.php?pid=faq_pda_list

 

Ok i'll check it out and try and hook it up and get you a reading, onlyt hing im wondering about is why my cel wouldnt be coming on and if this hesitation is in fact "normal" and im making a big deal over it

 

Well, a CEL is activated by reaching a "threshold" over a few cycles. It varies per CEL, but you get the idea. I have a feeling that the stock MAF will work in a degredated state while dirty, yet not be bad enough to throw a CEL. I mean, my MAF wasn't all or none. There are many factors that would contribute.

For example: When I got my first CELs, they would only be tripped on humid/rainy days. After a while, however, it didn't matter what the weather was like. The MAF was just getting worse and worse over time.

 

Yea i understand what you mean.. Honestly its not even bad in my car, i guess im just too picky, im just going to replace it for the hell of it

 

Ruiner... I must've been following your footsteps. I got P0172 - System too rich - bank1 & P0175 - System too rich - bank2. My CEL was triggered when I made a sharp left turn, kind of odd. I've been cleaning my MAF almost once a week. I guess time to call Stephen for a new MAF, probably call Nate to get the cotton filter too.