My 1998 plymouth neon has a number 4 cylinder misfire. changed plugs, wires, coil pack. still misfires. does it at slow speeds and really bad when trying to get up to speed when entering the highway. switched injectors around and still got number 4 cylinder misfire with code reader. can feather the gas pedal at slow speeds and floor it then feather to get on highway then it smooths out and seems to run fine. looking for an answer to this problem. thanks.

coil pack may be bad

check coil pack for resistance with an ohmmeter. if one pack controls two cylinders, the values should b the same. if not replace coil pack

The coil pack on these engines runs hot, so it's important to make sure there is heat sink grease under the coil to transfer heat. If the coil module gets too hot, it will fail.
If an engine is hard to start or has a misfire at higher speeds, the problem may be a weak coil, a bad plug wire, or a fouled or worn spark plug. On 1996 and newer vehicles, you should get a cylinder misfire code. A code for one cylinder would likely indicate a fouled plug, bad plug wire, or possibly a clogged or dead fuel injector, or a compression leak (burned exhaust valve). Misfire codes for two cylinders that share a coil would likely point to a bad coil.
Another way to figure out if a misfire is a bad coil is to swap two of the coils on the coil pack. If the misfire moves to the new cylinders, the problem is the coil. If the misfire remains in the same cylinders, the coil is OK and the problem is the wires, plugs, injectors or compression.
If you test a coil with an ohmmeter, the test specs are 0.5 to 0.9 ohms for the primary terminals under the coil, and secondary resistance of 5,000 to 8,000 ohms at the high-voltage terminal.

Look for an intake leak.

no. 3 plug, wire or coil pack. Remove the plug wire one inch from the plug using a properly insulated plug wire tool with the engine running, if you hear a tick, tick sound then it's the plug if you don't hear a tick tick sound it means it's the wire or the coil.

have you changed the fuel filter? Have you changed the ari filter?

If you have a coil pack with 6 cyl. 3 coils in one One coil for 2 cylinders One of the coils in the pack has gone bad. To verify this check which cyliders are missing and see if they match any pair on the coil pack. If so the coil should be replaced. Hope this helped. Moe

might be the coil pack is bad, wires, plugs, o2 sensors, dirty injectors, catalic converter ( only if you smell rotten eggs ) . cylinders are misfireing.

ignition mod. grounds,pcm or timing belt could all be it but, I would have to look at timing first.

spark plug or coilpack