Sable not firing on all cylinders sometimes

Hello,
My Sable is sometimes not firing on all cylinders. It never stop, but it could go with idle so low that charging light would start blinking. It is happening after driving for 15 miles (from work), stop for 15
minutes in day care, starting and driving 200 feet to first intersection with long red light. Then engine starts hesitating on idle with gear (auto) on. Sometimes even on first few yards of driving after light. Got it checked in dealer where I have extended warranty. They did cylinder pressure check and found no problem. My initial opinion was piston ring or valve is worn, but pressure check should rule this out. It is happening since I bought the car about 6k miles / half year ago. Outside this problem engine is fine with good power, starting, no oil consumption etc. On idle engine does not vibrate as evenly as my other car, but that may be normal. It does have 12 valve 155 HP engine with 40k miles on it. I can as well do nothing about it, but wondering about effects in long run. Any ideas?
Thank you,
    Stan
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I have a 98 that misfires at times---think it might be the coil pack or plug wires, not sure though. My ford mechanic told me not to worry about it but I don't like it---may end up spending $ to finally find out, but if anyone else knows anything here it would be helpful.
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On 27 Feb 2004 14:49:01 -0800, si_bendoviNO_S_P_A snipped-for-privacy@hotmail.com (Stan Benda) wrote:

I just solved that very problem on my 115k mile 12 valve 98 Taurus by changing the spark plug wires.
Buy the Motorcraft wires. I just made the mistake of buying aftermarket wires, they are a little too long and leave loops sticking out looking for trouble. They are a little fatter than the OEM wires and have a harder time fitting in the wire routing gizmos. The OEM wires have the proper cylinder# printed along the length of each wire, making them easier to install without mistakes.
Dan
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Dealer is saying: "If there would be any misfiring it would set Check Engine Light" and that changing ignition cables is waste of money. Light would come on if they would be bad. I could not figure out how computer (PCU) would be able to find out that there was no detonation in piston. Is there any online store selling motorcraft ignition cables?
Stan
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Ended up with new high pressure fuel pump on third visit to dealer. It is little better. Engine does not go to almost stall condition on red traffic light since then, but still does not have idle with all six contributing :-). Dealer says cables does have nothing to do with the problem. I would replace them by myself, but do not know how to reach them. 3 cylinders are hiden behind fuel system.
Stan
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