P0304: Cylinder #4 misfire
P0421: Bank #1, Right bank, warmup catalyst system efficiency below limit
P0431: Bank #2, Right bank, warmup catalyst system efficiency below limit
P0725: Engine speed input circuit malfunction
P0750: Shift solenoid "A" malfunction
Check the O2 sensor. Run some fuel system cleaner to clean the injectors and valves. Also check for vacuum leaks.
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Saturday, October 1st, 2011 AT 5:15 AM