02 Impala LS Misfires

My 02 Impala (3.8, 76,000 miles) runs well until you attempt to accelerate or go uphill. Then it starts to misfire. Sometimes. I got a flashing check engine light during one of these episodes, but it went out after a little while. Had the AutoZone guy put the computer on it, but it didn't throw any codes. I used a bottle of injector cleaner, replaced the plug wires and changed the fuel filter and none of these fixed it. Any ideas?

My experience wiith trying to get DTC trouble codes from an Auto Zone scanner has been nothing but wrong info. The Actron scanners they use ( at least in my area) can read only the generic powertrain codes . Two weeks ago AZ scanned my 2000 LS and found no codes. The next day a local GM dealer pulled two codes in Failure Records with their Tech2. I would highly recommend you find a dealer or shop that has a professional scan tool who can really tell you some information you can go by.

FIXED!
It was the ignition coil for cylinders 1 and 4.