misfire issue

[matt0106]

I had a 98 4runner 3.4l and now i have a 01 tacoma with a 3.4l that is having a misfiring issue. came back to T4R because I think this is the best site for solving problems.

Started out by pulling away from a gas station and running rough. checked codes and they were p0300, p0301, p0302, p0303. replaced spark plugs, wires, and coils and started it back up to come across codes p0300, p0304, p0305, p0306. with it practically running the same (rough and stuttering under load and at idle). then replaced fuel filter and also no change.

Does anyone have any idea of what the problem may be? Injectors? any advise for diagnosing this issue would be greatly appreciated!

 

[s20004runner]

I had a 98 4runner 3.4l and now i have a 01 tacoma with a 3.4l that is having a misfiring issue. came back to T4R because I think this is the best site for solving problems.

Started out by pulling away from a gas station and running rough. checked codes and they were p0300, p0301, p0302, p0303. replaced spark plugs, wires, and coils and started it back up to come across codes p0300, p0304, p0305, p0306. with it practically running the same (rough and stuttering under load and at idle). then replaced fuel filter and also no change.

Does anyone have any idea of what the problem may be? Injectors? any advise for diagnosing this issue would be greatly appreciated!

there are already ongoing threads so try googling '3rd gen 4runner misfire' etc.

Based on my readings and my experience (as I am experiencing this now), the consensus is get compression test to rule out the more serious blown head gasket.

For myself, I put in new wires and new spark plugs and I replaced one of the ignition coils recently.

Also, I did the spray to tb seafoam and it helped, but not completely fixed. My guess is that seafoam cleaned valves slightly. I am doing to do a second can and if the second seafoam doesn't work, then I will be switching out all six injectors (just so I don't have to do others again).

 

[Hesk11dog]

I had a 98 4runner 3.4l and now i have a 01 tacoma with a 3.4l that is having a misfiring issue. came back to T4R because I think this is the best site for solving problems.

Started out by pulling away from a gas station and running rough. checked codes and they were p0300, p0301, p0302, p0303. replaced spark plugs, wires, and coils and started it back up to come across codes p0300, p0304, p0305, p0306. with it practically running the same (rough and stuttering under load and at idle). then replaced fuel filter and also no change.

Does anyone have any idea of what the problem may be? Injectors? any advise for diagnosing this issue would be greatly appreciated!

Misfires can be hard to diagnose. Some things you haven't tried yet are cleaning the throttle body and MAF sensor. There is a method of testing the resistance of the injectors to see if they are still functioning. The FSM lists the resistances for this for hot and cold injectors. The resistances of the coil packs can also be measured and verified. Like S200 said, there are tons of links about misfires on this site. It is better to use google as the search engine for the threads too. Before you throw parts at it or money, do some research of possibilities.

 

[matt0106]

thanks for the advice, it turned out to be the coil packs that were bad on mine. I went back and re-traced my work and found that i mismatched two of the spark plug wires. Next time i'll be sure to draw out the diagram!