Troubleshooting a bad miss - 400E
12-19-2007, 09:01 AM
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1992 400E, 2003 S55, Porsche 911S
Troubleshooting a bad miss - 400E
My 400E (1992) starts and runs perfectly - for 3 minutes. Then something happens and it starts to miss horribly. Random misfires, but so bad that it really can't be driven. The only clue I can offer is that the miss begins at three minutes (2:53 to be more precise) after starting cold.
Either the ECM starts to run a certain routine, or checks a certain sensor at the time. The temp has not changed sufficiently in 3 minutes for it to be a heat-induced failure. EOS? MAP? TPS? Any ideas?
BTW - I've already installed a new fuel injection wiring harness.
Either the ECM starts to run a certain routine, or checks a certain sensor at the time. The temp has not changed sufficiently in 3 minutes for it to be a heat-induced failure. EOS? MAP? TPS? Any ideas?
BTW - I've already installed a new fuel injection wiring harness.
12-20-2007, 12:03 AM
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89 300TE, and 68 280sel
simple things here... I had a similar issue on my 400 and it turned out that once the engine got warmer( not even to op temp) the plug wires were shorting on one of the cylinders. Check the ignition system before you get too carried away. The cap and rotors are notorious for being neglected on these motors.
12-20-2007, 12:51 AM
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1995 E320 SE, 162,000 Miles (Sold)
I'm leaning toward O2 sensor as well. 3 minutes is probably about how long the sensor takes to heat up and the engine runs in the Closed Loop mode (where it provides feedback to the ECM). I would check the diagnostic codes at the OBD, if yours has one.
