Weird issue, only when cold

Rifter

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Hi guys. Have a intermittent issue i want some advice on.

Some background info, 4runner has 340,000kms on it, ive owned it since 280,000kms. Ive done zero engine work to it in that time.

Its rusted beyond the point of saving underneath, im in the run it till it dies and spend zero $$ on it stage of its life. Thats why ive done nothing with this issue till now.

So starting few months ago i noticed it would miss a bit under light acceleration only when cold. wasnt sure if it was engine missing or trans slipping issue it was such a light loss of power. And not a bad miss and only below 3000rpm when cold and very rarely not always, never missed at idle or hard on throttle only light acceleration.

Fast forward to this morning, start er up and it sounds like a diesel, very clearly a dead cylinder or i suspect 2 dead cylinders from the amount of unburned gas smell in exhaust. Its running so rough RPM is jumping from 800-3k as ECU tried to idle at 1.5k. Cant drive at all to much loss of power dies as soon as put in gear and try and move.

Its at this point throwing no codes so I start it up again and hook up my obd2 reader to see what the data is telling me maybe i can learn something that way. as i do this it throws a code, P0306, rough idle, no shit lol.

As im googling that and its warming up it stops missing, the 1 or 2 dead cylinders start to fire and it runs fine as soon as its at temp. I drove it 40 kms to work and it ran fine like nothing was wrong at all.

It didnt even throw P0306 long enough to log it as a confirmed code it just logged it as pending unverified code in ECU.

Any ideas guys?
 
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Also worth noting its not loosing any coolant, i dont think this is a head gasket or warped head issue as many people have reported for the P0306 code.
 
Gotcha. Head gasket was going to be my first suggestion with a P0306 as that code is especially brutal on 4th gens with the V6.

Possible water is getting into the fuel lines/injectors and freezing? Have you done a compression or leakdown test?
 
Im going to do a compression test when i get home, as this happened when i went to go to work i have had very little time to diagnose it.

When i get home i intend to pull the plugs, check them and the wires, then do a compression test. Then ill move onto injectors and coils if needed.
 
306 is a miss in cylinder 6, so it only detected an issue with the one cylinder. I would pull the plug and compare with another.

I ran a 3.0L on 5 cylinders for 6 months with no issues other than a rough idle lol. It was an OBD-I and never threw a code, didn't realize it until I changed the plugs and wires and saw the wire was damaged and the plug was broken!
 
P0306 Is missfire in cylinder 6. It’s not the coil side. So could be the spark plug wire, spark plug or fuel injector. Check resistance on your #6 cylinder fuel injector.
 
Update. Was the plugs, #6 plug had a crack going 80% through it, could put a little pressure on it and it would not be connected enough to fire. All good now runs great, better than it has since ive owned it.
 

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