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Old 01-16-2002, 04:18 PM   #5
Jon [in CT]
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Join Date: Nov 2000
Chapter/Region: NESIC
Location: Connecticut, USA
02 WRX Sedan


Since the ECU is reporting that all four cylinders have misfired, I think it's very unlikely that there are loose connections at all four sparkplugs.

It might help to understand how the ECU detects misfire. The general strategy is based on crankshaft rotational velocity (reference period) variations. The ECU determines crankshaft rotational velocity using the crankshaft position sensor and camshaft position sensor. When a cylinder misfires, the crankshaft slows down momentarily. By monitoring the crankshaft and camshaft position sensors’ signal, the ECU can calculate that a misfire has occurred and which cylinder was firing when it happened.

So, if I were a tech, the first thing I'd check is that the camshaft position sensor (on the driver's side) and the crankshaft position sensor (on the oil pump) are both still bolted down properly.

The general procedure for diagnosing misfires in the absence of any other trouble code is described in this thread:

Also, some ECUs have been reflashed because they misinterpretted the camshaft position sensor signal. Misfire codes might be a manifestation of this ECU problem.
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Last edited by Jon [in CT]; 01-16-2002 at 06:23 PM.
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