Cylinder Misfire Detected

[clanofwolves]

My '00 V6 started running rough three days ago at idle and under power. The Check Engine light was blinking and upon checking, the codes it threw were as follows:
PO306 Cylinder 6 Misfire Detected
PO306 Cylinder 6 Misfire Detected
PO300 Multiple Cylinder Misfire Detected
PO305 Cylinder 5 Misfire Detected

As background, the wires and plugs are two years old and I thoroughly checked them first due to a wiring misfire issue just prior to their subsequent replacement. Anyway, I purchased a new coil for Cylinder #6, checked that each coil was getting the same 12 volts on #6, #4 and #2 and replaced the apparent faulty coil on #6 with the new one. No change. Damn.

I then returned the new coil back to its box and installed the old #6 coil at the #4 plug location and installed the previous #4 coil on the #6 plug location. Although there was no change in roughness at idle and under power, I had hoped that the problem would migrate from #6 to #4 exposing the new coil as faulty. However, when I had the Check Engine Light checked again, it threw the same Codes as denoted above exposing the #6 and #5 Cylinders being the problem. Again, damn.

The "old school" me keeps thinking that if it's not spark, then it must be fuel or air (logic). But -as far as fuel is concerned- what are the remote possibilities that Cylinders on opposite heads but in the same position would both begin having misfires at the exact same moment (like injector problems)? And the same statistical issue arises when pondering a lack of combustion air or a vacuum leak on two Cylinders on separate heads. I'm baffled at this moment; which is beer-thirty here in NC.

Any ideas?? I'd love 'em!

Dave

 

[TheDurk]

Well, my first thought is that the coils are on Cyls. #1,3 and 5, so you may be repalcing the wrong coil. The coil that fires #6 is the one mounted on #3.

 

[clanofwolves]

Thanks for the enlightenment and the diagram especially. I'm going to give this a try and see if the Misfiring Cylinder moves: Coil #1 to Plug #3, Coil #3 to Plug #5 and Coil #5 to Plug #1. I'll let you know if the issue is effected. Thanks!

 

[clanofwolves]

No change; swapped coils; still #6 Misfire Code......

 

[LookAtThatDog]

It seems like most misfires on the 3.4 are due to injectors. It'll be kind of a chore to replace 5 and 6

 

[TheDurk]

I'd still swap the plug even though it's two years old, checking it and the wire boot carefully. Let us know how it looks. If it is dry, injector is the next prime suspect. You can also confirm spark old school by holding the plug wire near a good ground while cranking. Old school, but suggested in the Toyota FSM on Page IG-1.

1. INSPECT IGNITOR AND SPARK TEST
Check that the spark occurs.
(1) Disconnect high-tension cords from spark plug.
(2) Remove the spark plug.
(3) Install the spark plug to each high-tension cord.
(4) Ground the spark plug.
(5) Check if spark occurs while engine is being
cranked.
NOTICE:
To prevent excess fuel being injected from the injectors
during this test, do not crank the engine for more 5 - 10 seconds
at a time

 

[LittleCaesar]

Maker of the said plugs and wires? OEM? Denso?

 

[clanofwolves]

Maker of the said plugs and wires? OEM? Denso?

The plugs are dual arm iridium and wires are OEM, both with 20K on them thereabouts.

Here's what I've done:

1) cleaned, checked, relocated and re-installed the coils; no change: Misfire Cylinder #6.
2) removed, checked, relocated and re-installed the spark plugs; no change: Misfire Cylinder #6
3) removed fuel injector #6 and replaced it with an OEM injector; no change: Misfire Cylinder #6

What in the world is going on 4?

Ideas???