Originally Posted by MH996TT
I am guessing that you have installed the 986 606 125 01 Boxter MAF by now. I'm wondering how it went? I did the same thing, installed it last night in my early 2001 996 TT. It took about 8 miles of city driving and I through a CEL and started having a high idle (1200rpm). I havn't tried it since I reset the CEL -- maybe the ECU will learn? maybe the ECU needs flashing?
I'll post fuel trims tomorrow.
A few notes 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. I also talked to a person at Porsche who said that depending on the ECU, it may or may not be able to be flashed. He said that some DMEs have submenus, some do not. Either way, it wasn't worth the headache.
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.
No CEL as of yet. I have put around 45-50 miles on my car now. I have done city driving, a few "punches", and stop-light idles. My LTFTs are both sitting around -4 to -6 or so with the OEM 996TT MAF. My STFTs range from -6 to +5 at idle. That is in contrast to the +4 to +6 LTFTs and -12 to -20 STFTs (at idle) that I was previously getting before the CEL would trip under idle with the dirty, OEM MAF. The Boxster MAF is not the way to go from what I have personally experienced and logged.