I got a 99 3.8 115,000 miles and I am having the same problems with the misfire but my check enginge light comes on and starts flashing after just a minute or 2... Also sometimes when I start the car the trip mileage will reset itself to zero and the gauges will all spike and drop real quick then kick on. I have replaced the plugs and coil packs plus the altenator and got a new battery. What could it be? computer sayin misfire cylinder 3 (again) and idle speed sensor. would the idle speed sensor be causing the gauges and mileage to go crazy? It also does the jerk when it goes into 2nd gear. Hope someone can help this has been driving me crazy forever

 

Is your SES light coming on or is it another light? A flashing SES means that continuing to run the engine could result in damage to the vehicle, so I would DEFINITELY stop running it if it is a flashing SES. Here's a few possibilities, though:

Faulty spark plug, spark plug wire, ignition coil, ignition module, fuel injector are the most common.

Coolant leaking into a cylinder is another, so check your gasket. It's not blown, leaking, or damaged, is it?
Internal engine problems such as burnt valve, broken valve spring, bent push rod, worn rings, etc. You might want to get the engine completely tuned and have them look at it, tell you what's wrong, then you can fix it yourself and save some $$$. Good luck!

 

Yes It's the SES light and when you first start it it's ok and stays steady its once you take off it starts flashing and acting like it has lost power. Trip mileage will reset its self when you start it sometimes. I have changed the coil packs plug and plug wires (high temp but not covered with protectors or nothing) hooked up to computer and it says misfire number 3 cylinder and idle speed sensor. You can smell the car burning gas I am guessing thats from it missing? Have been told burnt valve by a couple ppl but want to make sure before I go to tearing things apart. Ill check those gaskets out. anymore help would be great!!! Thanks guys!!!