#4 misfireing

[Scott Stephens]

I have a 99 trooper 3.5l. I am having roughe idle situation with a check engine lite on. Sofar I used a code reader and the code was 0304 which my book says is #4 missfire. So I checked the plugs and replaced them I also swapped the # 4 and th#2 coil pack around still the same code. Then I pulled the #4 coil installed a plug to group and started the engine good spark? So where do I go from here? I am wondering is missfire mean dirty injector? but I do smell extra gas.

[travelman]

I don't remember my code number but I had a misfire on cylinder #4 of my 99. I did the coil swap, check the spark and got nowhere. My cure was to gently tap the fuel rail by the #4 injector. I used the handle of my screwdriver for the tap and the engine was running. This instantly cured the problem and about a year later no recurrence. I have since used a bottle of Techron every 3 or 4 months. I was already changing the fuel filter every 24kmis or so.

My theory was that a tiny bit of something fouled the injector. The gently tap was just enough to break it up. No guarantee but unless you hit the rail too hard (or the much more fragile injector rather than the rail) what have you got to lose?

[amigo-2k]

what brand of plugs did you use?

[Scott Stephens]

I bought a set of ac plugs double plat oe replacment the plugs that came out were chapion double platnium.