Pontiac Repair: 2000 Pontiac Grand Prix Miss, pontiac grand prix, ac delco

Question
Hi Tood,
I have a 2000 Pontiac Grand Prix GT 3.8l non supercharged w 127000 miles.  On warmer days it tends to buck and miss @ 3500 -4200 rpm, as when accelerating to pass a vehicle.  Acts as if it hits rev limiter, as when in park or neutral.  No codes in computer and fuel pressure in range @ idle.  Mechanic noticed that one coil pack looked older than other two.  Had a problem app 2 yrs ago that you helped me with when fuel pump shut down on hot day in july.  It hasn't done it since.  Of course the car didn't miss for the 2 weeks my mechanic had it!  Fuel filter has 2500 miles on it, plugs and wires app 22000.  Should it be looking at fuel pump, coil pack, or maybe rev limiter?  I just had the cooling system flushed, new radiator installed, and the dexcool replaced with peak green antifreeze, so I think it's not an overheating issue.  My mechanic is pretty good, but he spoke with another mechanic that can hook up car to computer and drive it, hopefully then finding the problem.  This may not help, but the horn and the cruise control went out.  Broken wire for horn, and eliminated clockspring as cruise culprit.  Would value your opinion as to where to look, as the mechanic with the computer to drive the car is ungodly expensive, and I'm pretty handy.  Any other details you may need I'm more than willing to give.

Thanks Todd,

Tim

Answer
Hey Tim:

I like repeat business;)

if this misfires under a load I would suspect a secondary igniton issue. Plugs wires or a coil. If this does it frequest enough it should store misfires in the engine computer if it has more then 1 cylinder dropping out then chances are you have a coil breaking down under a heavy load. ecah coil fires 2 spark plugs ar the same time. so if the cylinders that are misfires are sharing the same coild I would suspect that. Were the plugs and wiresd replaced on this due to this issue or did it crop up after the replacement. I only recomend AC Delco ignition parts plugs and wires any kind of after market parts will cause issues especially "magic split fire plugs" those are horrible! one other though could be a MASS Air flow sensor but those cause stalls and hesitation but I have seen them do strange things. That is where I would start looking. good luck :-)