Code P0306 #6 Misfire HELP 4.0 V6

[BluePatriot]

I have a code P0306 for #6 cylinder misfire detected. What happens is on a cold start you can feel the misfire and sometimes the light comes on and still scans as a P0306. I've replaced spark plugs, and moved the #6 coil with the #2 coil and still the same thing. This only happens on a cold start, and then after a few seconds, about 5 the engine returns to normal on it's own and drives just fine. I drove a 660 mile trip with it and nothing happened. I havent lost a drop of coolant so I really dont think it's a head gasket. If it was a bad cylinder or valve spring then it would be constant, right? Same if the timing was off, it would be constant. I've narrowed it down to maybe an injector possibly just by process of elimination. And again, after a cold start the engine is rough for about 5 seconds and smooths out to normal. If I shut the car off and on then it's fine. I need opinions and solutions. And if anyone agrees, where can i get instructions on how to replace an injector? I've searched everywhere for a 4gen 4.0 v6.

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[07V8]

Start with a leak down test.

 

[BluePatriot]

Start with a leak down test.

What would that test show me?

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[07V8]

What would that test show me?

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That error code is notorious for head gasket leaks. A leak down and cylinder pressure test help diagnose that issue.

There is a multi page sticky thread at the top of the 4th Gen section with lore info on HG failures and diagnostic practices.

http://www.toyota-4runner.org/4th-gen-t4rs/188699-***-v6-head-gasket-action-request-***.html

 

[BluePatriot]

That error code is notorious for head gasket leaks. A leak down and cylinder pressure test help diagnose that issue.

There is a multi page sticky thread at the top of the 4th Gen section with lore info on HG failures and diagnostic practices.

http://www.toyota-4runner.org/4th-gen-t4rs/188699-***-v6-head-gasket-action-request-***.html

I saw that already. But if it was a head gasket you would always lose coolant and usually have a white puff of smoke from the exhaust. I've never had either of that


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[olyeller]

I saw that already. But if it was a head gasket you would always lose coolant and usually have a white puff of smoke from the exhaust. I've never had either of that


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"usually"
how many other times have you owned other gen 4 v6 4runners and have thrown that code?
people are giving you good advice.

 

[Troymclure]

I saw that already. But if it was a head gasket you would always lose coolant and usually have a white puff of smoke from the exhaust. I've never had either of that


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I had no misfire, no loss of coolant, no check engine light, no white smoke, no sign of any issue. Then one day I pulled the radiator cap, and it smelled like exhaust fumes. Did a block test and leak down and had a blown headgasket between cylinder 6 and 3. When the headgaskets fail on these trucks, it is very subtle. But if you catch it early, it will prevent other damage from being done.

 

[mijbr90190]

Just went through this with my 06. Rough cold start, no CEL, no white smoke and the slightest amount of coolant being consumed. Shop scoped cylinder 6 and waited some time before seeing a drop of coolant. 2700 bucks covered by the dealer I bought it from.

 

[JSimpson07]

Thankful for this post and the replies. Had a misfire code for cylinder 6 pop off just after buying my 4th gen from a private seller. Had 250K on it so I figured I’d have my issues. Changed the spark plug and coil and it felt smooth for a few days but would continue to misfire 10-20% of the time at 40-50 mph. Tried Seafoam for the injectors with no change. Saw the posts here and started looking for signs of a blown/leaky gasket. All the other warning signs like milky oil, white smoke exhaust, and empty coolant weren’t there. Block Test was even negative. But I didn’t feel like stripping my injectors etc etc. Finally found some threads that recommended Blue Devil. Did the radiator flush and followed the instructions on the yellow label to a T and haven’t had any issues whatsoever for roughly 1000 miles so far. Hope this helps someone else going through something similar.