coil pack 1+4 random missfire

[mattbln]

I have a 1998 grandprix non supercharged 3800.cheak engine light flashes. scanner says pd0300(random missfire).Next went to missfire data , only to find cyl. 1+4 miss as fast as the scanner can count . The plugs +wires are new . I swaped coils from 5+2 over to the 1+4 , still same problem . I tried a ignition module +coil packs from a different car,still same problem . The engine is low mileage junk yard motor, intalled at the used car lot. The 3800 is out of a buick.The car seems to run fine,but the cheak engine light flashes. I do not feel a miss when driving it.I think it might need a crank sensor,but i am not sure.need help!

[BNaylor]

When the SES light flashes it indicates a misfire condition. However, you could be getting false misfires if the engine is not actually missing. When the engine was replaced was a CKP System Variation Learn Procedure (case learn) performed? A case learn must be performed with a GM Tech II machine whenever a new engine is put in or when the PCM has been replaced. The new settings are programmed into the PCM. It does not sound like the crankshaft position sensor has gone bad.

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[KX2000GTP]

^^^Yup, what he said

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