mtn_rooster
New member
CEL, rough idle, and P0306 for the last couple months on my 2006 4Runner - Limited (180k miles). I bought it used from a Toyota dealership at about 165k miles about 2.5 years ago.
1) Replaced spark plugs. They clearly needed replacing. Got better.
2) Swapped ignition coils with cylinder 4. Still P0306.
3) Compression test - All cylinders within 3.5% of each other : 137-142 psi. 90 psi on the first stroke and a quick build-up on successive strokes.
3) Replaced fuel injector on cylinder 6 (it was visibly blackened). Got a little worse actually. CEL started blinking when cold and clears after about 30s. That's new.
4) Positive block test. Test fluid turned green.
The positive block test points towards a leaky head gasket, right? If not and there are other tests I can do, I'd appreciate any feedback before I call my mechanic and shell out a few grand.
Thanks.
I should also point out that it's not overheating. I'd also like to mention that the number of misfires (from Mode $06 tests) went from the teens to 10k misfires after replacing the fuel injector. Any idea what would cause that?
One last sign/symptom is that the spark plug on cylinder 6 is visibly dirtier than the other five (even on the brand new plugs). I wouldn't say it's bad, but you can definitely pull it out of a line-up. The last time I pulled that plug there even seemed to be a bead of, what smelled like, gas bridging the gap.
1) Replaced spark plugs. They clearly needed replacing. Got better.
2) Swapped ignition coils with cylinder 4. Still P0306.
3) Compression test - All cylinders within 3.5% of each other : 137-142 psi. 90 psi on the first stroke and a quick build-up on successive strokes.
3) Replaced fuel injector on cylinder 6 (it was visibly blackened). Got a little worse actually. CEL started blinking when cold and clears after about 30s. That's new.
4) Positive block test. Test fluid turned green.
The positive block test points towards a leaky head gasket, right? If not and there are other tests I can do, I'd appreciate any feedback before I call my mechanic and shell out a few grand.
Thanks.
I should also point out that it's not overheating. I'd also like to mention that the number of misfires (from Mode $06 tests) went from the teens to 10k misfires after replacing the fuel injector. Any idea what would cause that?
One last sign/symptom is that the spark plug on cylinder 6 is visibly dirtier than the other five (even on the brand new plugs). I wouldn't say it's bad, but you can definitely pull it out of a line-up. The last time I pulled that plug there even seemed to be a bead of, what smelled like, gas bridging the gap.
Last edited: