Macster

There is an adapter that plugs into the DME harness and offers some pins to connect to to support the viewing of some of these signals in their "raw" form.

However, I could find no info -- I do not have any wiring diagram -- to know which signal is the square wave signal pin.

In the 996 Turbo factory manual for OBD error code trouble-shooting in the sections devoted specifically to MAF trouble shooting all the tests just have the tech measuring the output voltage and if it is not with in spec offers the MAF should be replaced.

Indirectly one can view the adaptation going on by monitoring the short term fuel trims. If these are varying by too much this can be a sign the MAF is delivering bad data. The fuel trims should move from rich to lean and back again over and over again as the DME varies the fuel mixture slightly from too rich to too lean. The DME uses the #1 O2 sensor readings to confirm the oxygen content of the exhaust changes in time/sync with the fuel mixture changes.

If the the fuel trims are swinging pretty wildly -- over 5% is a good amount and 10% for too long can trigger a CEL -- this can be MAF related. However, it can also be due to an air leak or some other problem.

You can see the DME (re)adapt if you use an OBD2 code reader/data viewer and issue a clear DTC command. This resets the fuel trims and other learned data to their defaults. As a result as the engine runs the DME will strive to relearn the proper fuel trims and in doing so it can have the fuel trims swinging pretty high and low. But the swings should become more subdued as the DME relearns.

split71

Thanks Macster, I'm gonna update this thread after the new year when I can find time to do the plugs.

split71

Update coming this afternoon...

split71

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Updates Updates Updates!!!
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So it wasn't plugs. See some pictures of the plugs below, had several thousand miles left on them, a little sooty but not bad by any means. Mechanic said the same thing.

The problem was something in the fuel line was stuck. They took apart the line and forced some compressed air down the line and found something was stuck. They got it out of the line, replaced the fuel filter (which was like all black according to them), and found that the sending unit was completely fried in the tank.

Adam and his team @ Ace Motorsport in Vista, CA took care of it from the get go. They figured it out within a day and had it fixed once parts arrived. The car drives like a madman again and all is well.

THANK YOU to everybody who has helped in this thread (as well on other boards ). Pictures of the old plugs below for those who don't believe me

Kevin

Congrats on the fix. It would be interesting to see pictures of your float and in tank fuel pump pickup screen. So you have NGK plugs in your engine? Did you measure your old plugs for "gap" That's the diagnostic info I'd like to see? The electrode ground strap on the Bosch FR6 plugs is different "twin" vs single on the NGK..

Macster

Thought I posted this but when I came back it was not here. Must have not hit thesubmit button before I closed my browser.

Those do not look like the right plugs. IIRC the Turbo takes a twin ground electrode plug.

Also, the gaps look inconsistent though this may be due to the angle of the plugs.

I note the plugs are discolored all the way up the threads so I would have replaced the plugs.

split71

(xposted @ 6SO)

Macster, you're correct. These technically are not the correct plugs and I put in the correct Bosch's you see in the background there. Regardless, the car ran fine with them for ~10k+ miles.

They were close to being due, but it is not the culprit and that's what I'm trying to highlight here. The guys cleared the fuel line and test drove the car after and it ran fine, then we replaced the sender and plugs for good measure.

Macster

Wasn't clear to me -- my fault not yours -- the plugs were changed.

That was a good catch regarding the fuel line blockage. Treat the shop to a couple of dozen donuts.

rmc1148

Would like to know what was obstructing the fuel line?

split71

I'm not sure, they did not tell me what was blocking it or if something flew out the other end of the line. I trust their judgement though - I was recommended to them by friends of their family.