My impalas check engine light flashes after 3rd gear and is very slow to accelerate. Also shakes as accelerating. And acts like it wants to die at a stop only in gear. I have had to replace 2 ignition control modules in the 3 years I've had the car and haven't had the spark plugs changed in a year and a half. I just replaced the ignition cool for cylinder 5 because it read a misfire on that cylinder. With no avail. I am at a loss as to what to do with out spending thousands at a shop. Please and thank you in advance.

If you haven't done a full tune up in 1.5 years, which includes plugs and wires, I suggest doing that first. I've had a sparkplug be bad straight out of the box. There was a hair line crack in the ceramic that caused a lot of misfires.

I hope you're getting your ICM from Autozone because of their warranty otherwise your just throwing parts at it. Are YOU doing the work or having a shop do it?

Have you checked coil output with a spark tester?

When you replaced the plugs, did you use OEM?

Several TSB'* on carbon tracking on the inside of the boot, and on the porcelain of the plug......also have you noticed any corrosion/arcing on the coil terminals?

Are the wires original(would have cylinder numbers on them)? If they are, as Mike suggested, replace wires and plugs(use OEM).....if problem is still there, do coil output test on each terminal....

Please also share other details of the car, such as other work done, what other issues the car has, if it is consuming coolant, etc, and how the fuel mileage is behaving.

Just about anything can cause a misfire, and if you are busy fiddling with the ignition system because of the misfire, while the engine is busy ingesting coolant from a failed UIM, we aren't going to get anywhere fast.

Low fuel pressure can also cause misfires. On a 2001, if it still has the original fuel pump it is worth checking fuel pressure.