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Won't Idle - P0102 Code


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#1 gwegryn

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Posted October 14, 2007 - 03:52 AM

All,

Symptom:
'97 stock Boxster (no engine mods, no K&N, etc., 70,000 miles, up until this year 100% dealer-serviced) has a problem with idling -- after normal starting (no foot on the accelerator), the engine dies, but will run if I keep a light foot on the accelerator to keep the revs up while starting. No CEL when revs are maintained to keep engine running.

Background:

I detailed the car over 2 weekends. On the first weekend, I partially lifted the rear convertible deck to detail beneath it, left the key in the ignition, then called it quits and left the car in the garage until the next weekend. On the next Saturday, I tried starting the car, but it appeared the battery had drained. I pulled the battery and trotted over to Pep Boys, where they ran a full load test, passed and charged the battery back up. Re-installed the battery, reset the radio, and thought my problems were over. That's when the engine began to die at idle.

My ODB II reader found only one code reported - P0102. I pulled the MAF -- it was clean with the sensor wire very shiny (was replaced at 50,000 miles by the previous owner, due to a CEL). I tried unplugging the MAF as found in other posts, but no improvement. I disconnected the battery for 2-3 mins, then reconnected, but again, no improvement.

This is the first time I have experienced this problem.

History:
Purchased in 2002 from 2nd owner with 48,000 miles. 100% dealer serviced.
The MAF was replaced at 47,000 by the previous owner, due to a CEL.
The secondary Air Shutoff Valve was replaced at 68,000 miles, again due to CEL, just 2,000 miles ago.

Potential Next Steps:
a ) explore throttle body for function and blockage, clean, etc.
b ) further test O2 sensors, as they seem to influence the MAF.
c ) find a good independent Porsche shop with the Porsche ODB reader to get a better idea of what's going on.
d ) find enlightenment on this super forum for advice :)

Thx in advance,
Glenn


Edited by gwegryn, October 14, 2007 - 04:07 AM.

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#2 Loren

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Posted October 14, 2007 - 06:36 AM

P0102 Mass Air Flow Sensor - Below Lower Limit Possible causes: - Open circuit - Short circuit to ground You either have a bad MAF or wiring harness.


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#3 wvicary

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Posted October 14, 2007 - 10:41 AM

I had a similar code on a VW and it turned out to be a blown fuse..... wouldn't hurt to have a looked at them.


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#4 juniinc

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Posted October 14, 2007 - 11:08 AM

Graph of Idle Problem:
I learned of a "DME upgrade" for the engine control software/calibration. Porsche has identified this problem to be engine computer calibration related. Here is a list of other possible causes -
idle.gif
1. Idle Air Bypass Valve Hysteresis (Sticking)

2. Mass Air Flow Sensor – Inaccurate at low engine speed transient conditions

3. Intake Manifold Pressure Sensor, Intake Manifold Temperature Sensor, or Throttle Position Sensor in-range failure/out-of-specification – could effect air flow prediction calculation (not likely, Mass Air Flow Sensor should perform this measurement)

4. Higher than expected accessory load from the air conditioner, etc.

5. Intake manifold air leak (not likely, would result in higher idle speeds, not lower)

6. Software expecting low accessory loads and/or gain is too slow to react at higher accessory loads. (not likely, problem would be much more wide-spread?)

7. Fuel injection quantity too low or Oxygen Sensor incorrectly reading Air/Fuel ratio (not likely a fuel system problem, most likely air-control related)

I had a similar code on a VW and it turned out to be a blown fuse..... wouldn't hurt to have a looked at them.


Edited by juniinc, October 14, 2007 - 11:15 AM.

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#5 gwegryn

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Posted October 14, 2007 - 03:52 PM

I had a similar code on a VW and it turned out to be a blown fuse..... wouldn't hurt to have a looked at them.


Thanks - forgot to mention that I did check all relevant (and a few irrelevant) fuses.

Glenn
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