Technacrat

Looking for some diagnostic guidance. Have a 1996 4Runner with the six cylinder 5vzfe Engine with 165000 miles. Unit has always been well maintained and serviced no less frequent than manufacturer suggested schedule. Currently have a check engine light and a P0304 code (Misfire Cylinder 4). Checked plug, looked OK. Was going to check injector (requires pulling intake plenium) but held off. Noticed that once vehicle heats up symptom (rough running and missing) clears up. Could problem be in one of the temp units sending signals to computer? Do not feel problem is the injector because it clears up when hot. Also noticed that condition is usually worst if not limited to first start up of day. After running a while later starts do not seem to have the miss. Could problem be a burned valve (leaving oil seep down into the cylinder while sitting over night)? Last compression check was within spec. Unit has relatively new wires and coils (under 15K). Plugs have about 10,000 miles on them. Appreciate any comments and advise. Thanks

BajaRunner

First thing to do is to swap your coils, to see if the code moves to a different cylinder, thus saying the coil is bad. There are 3 coils, and they control 2 cylinders each. I forget the cylinder numbers but I am guessing that the #4 cylinder would be controlled by the middle coil (coils located on passenger side of engine on top of plugs).

Move the coil, and clear the code, (disconnect neg battery terminal), and see if hte code changes.

Another thing you can do is to test the resistance of the coil to see if the primary and secondary circuits are in spec.

Scroll to page #4
http://ncttora.com/fsm/2003/Repair_M.../ignsy/ovi.pdf