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Below is the firing order for 3.1L Grand AM.
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This is the correct info on the firing order.
The valves appearing to be moving in unison is normal # XXXXX just happens to be on the intake stroke and the #3 is on the exhaust. 1-4 ,2-5,3-6 are companion cylinders which means when #1 is on compression (valves closed) # XXXXX is on the Exhaust stoke (exhust valve open.
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Cylinder #1 is always the most forward cylinder,
A Birds eye view of the engine, looking down, one head is going to be slightly forward of the other, on your engine the head against the firewall is more forward (closer to the crankshaft pulley) than the one in the front (closer to the radiator).
I have made a crude diagram to illustrate my point,(not the best at this)