#3 Cylinder Misfire

[mudmaster]

Rig is a 2000 4Runner with the 3.4. It seems to only throw this code if I'm in the throttle or on it up a hill, basically when it's under a load, but not always. I'm getting ready to change the plug wires, the plugs are about 3 months old. Anyway, does anyone have any other ideas on what it may be?

 

[ToyotaDon]

#3 is on the "coil-on-plug" side, so changing wires may not help. Check the coil for any arcing around the boot. You can switch #3 coil to #1 cylinder, then see if the code follows. Look for cracks on the porcelain of the spark plug.

HTH

 

[mudmaster]

Thanks for the tips. It did this prior to the plug change so I'm pretty confident they are ok.

 

[Jetboy]

In a wasted spark circuit, the cyl under compression has significantly greater resistance than the one under atmospheric pressure. So it would make sense for it to be possible for the coil to produce sufficient voltage for a spark on the alternate side while failing to produce on on the coil side if there were some reason that the coil side was experiencing enough resistance under compression but not under atmospheric pressure to cause a misfire some of the time.

I'm struggling to think of a good reason why you'd realize this issue with a problem on the alternate (non coil) side. The only thing I can think of is the possibility that the coil wire is failing is some way as to create higher resistance near the margin of function and the very slight difference in sides causes it to misfire on the one side.

I'd go ahead with plug wires. They are relatively inexpensive to try. Next step IMO would be swapping two of the coils to see if the misfire moves with the coil.

If neither of those change the misfire, I'd look at the plug and possibly gap it just a little smaller.

If that doesn't work, then I'd move on to the signal to the coil to see whether it's missing a firing signal from the cpu.

good luck.

 

[mudmaster]

Thanks! I changed out the wires and so far no code.

 

[mudmaster]

Ok, it's done it once since I replaced the wires. Time to move to coil pack to another position.

 

[mudmaster]

New coil pack installed and so far good to go.