rough idle

[Ara]

Hi, I have a 2006 toyota 4runner, 6 cylinder.
Here is my problem: I am getting a rough idle when I start the car, especially if it has sat for more than a couple of hours. I have had the code p0306 show up. I know this is a cylinder 6 misfire. There are times when I start the car and I can tell that only 5 cylinders are firing. If I cut the engine and re-start, eventually all of the cylinders will fire.
Here is what I have done so far:
-replaced all 6 spark plugs
-checked the coils and wires with a multimeter, no problems, I have also switched out coils to see if I would get a different cylinder misfire
-does anyone have the specific resistance of the coils? toyota part 90919-02248
-I have cleaned the MAF sensor
-I am not losing coolant, nor is my engine overheating
-I have put a can of sea foam injector cleaner

-Does anyone know what else I can check??? Your help is appreciated,
Ara

 

[fdbyrne]

Sorry man. It's most likely the head gasket.

 

[Ara]

I figured that, is there anyway to know for sure? How could I check?

 

[fdbyrne]

When you replaced the spark plugs, did any of them look different than all the others? Often times the number 6 plug will look different if it's the head gasket.

You can also let it sit overnight and then pull the number 6 spark plug and look down into the cylinder with a bore scope to see if there is any fluid in the cylinder.

There are other ways to check but those seem to be the most accurate ways on our trucks. You could also check the coolant for hydrocarbons. I have heard of people having bad gaskets on this engine and the coolant still passing the hydrocarbon test, however.

 

[YotaDriver]

I figured that, is there anyway to know for sure? How could I check?

It seems like the first thing a lot of mechanics looking at these situations want to do is to swap around some coil packs or put in new spark plugs. I'd suggest moving straight to a leak down test to prove the #6 cylinder has been compromised. As [MENTION=118509]fdbyrne[/MENTION] mentioned above, a hydrocarbon test will work, too.

P0306 is an ominous sign for the 1GR-FE engine, but statistically it's been more common in the '03-'05 vintage engines as there was supposedly some sort of head gasket redesign at some point during the '06 model year.

Either way, sorry to hear because this is a big fix.

 

[Ara]

Thanks for all of your replies, the only thing that I failed to mention in the original post is the cylinder #3 plug had a bit of dried up oil on it when I went to replace it. There was also signs of burn in the cylinder going down to the spark plug. Since replacing the plug, I have checked the #3 cylinder to see if oil is getting on the new plug and it isn't. I also swapped out the coil from #3.