Why do you think it is running rich? Is it blowing black smoke from the pipes?
Over rich at idle could be a leaking infector, damaged o-rings on the infector(s), a bad/skewed MAP sensor signal, fuel pressure too high, TPS, ...lots of stuff
could cause it.
The ECM ignores any signal from the O2 sensor(s) until they are at operating temp(closed loop), so even a bad signal from the O2 shouldn't effect a cold start rich condition. You would need to monitor all of the pertinent sensor at a
cold start to see if one or more are out of whack...once the engine is warmed up, those reading may not be of any help.
I would start with a fuel pressure reading, then check the infectors for leakage, and go from there.
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Joel Adams
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