issues, and then more issues

i have a v6, 2000 LS. the car has been misfiring on hills/on the highway AND when it is raining/wet outside. I took this in to the dealer wednesday, and they replaced coil 4. This morning, i was on my way to work and i accelarated when going up a hill, and to my surprise, the RPMs dropped and the car started to shake violently (the exact reason i took it in!) Is there a connection between the misfiring when wet and the misfiring when accelerating? Also, could they have fixed (tried to fix) the wrong coil? is there guess work involved in figuring out which coil is bad? i spent about 500 to get this thing replaced and it's like they didnt do anything...

This is a very common issue, and has been addressed numerous times on this forum. I suggest you perform a search on this forum for more details.

In a nutshell, often times a misfiring coil is due to leaking valve cover gaskets. The oil leaks into the spark plug wells and gives the coils an alternate path to ground. If your car has leaky gaskets, replacing the coil will not be a long term solution. Also, as you'll read in the other posts, there is a revised valve cover gasket that is less prone to leaking.

As for troubleshooting the bad coil, the OBD-II diagnostics will provide a code either for an undetermined misfire (P0300) or for a specific cylinder (P030x where x is the affected cylinder number). This does not guarantee a bad coil though, a misfire could also be due to a faulty fuel injector or low compression, anything that could cause the air/fuel mixture in the cylinder to not fire.

That being said, the dealership should have a WDS system or the newer system which would allow them to turn off individual coils or injectors so they should be able to pinpoint the faulty item with high accuracy.

-Rod