Dear 4th gen v6 wizards....

2004 SR5 4X4 v6 160k miles
Bone stock.

P0306 stutter at cold start.

Ive read all the dreaded HG posts.

Pulled plugs and borescoped. Noticed some buildup on #6 where the misfire was. No pooled coolant or anything but there was some crud in there. Other cylinders looked normal.

Attaching photo of #6 cylinder. Does this build up look like HG or just crappy plugs/coils buildup?

*clean spot in center is where I bonked the borescope seeing if it was tough or sludge.

 

Welcome aboard

Start out by swapping the coils and plugs from cylinder 6 with another cylinder and see if the misfires follow to the other hole. This will help you narrow down if its plugs/coils or something else

 

By the looks of that photo, do you think that could just be a coil issue?

 

The plug always burns out on #6
If you dont replace the plugs pretty often, the plug burning out eventually eats the coil up.
Normally neglected vehicles come in with a misfire on #6
Pull the plug and the electrode is practically gone and you have 0.110" gap and the coil is trash
Replace all 6 plugs, put a new coil on #6 and it usually goes back to normal.

If its still got the original plugs it should have a different set in the drivers side vs the passengers side.

 

When ive seen head gaskets leaking badly the top of the piston is typically clean from the coolant getting in there. Id try swapping the cylinder 6 coil and plug into another one and see what happens. It very well might be one of those two. Ive seen both fail and cause misfires

 

As Airdam mentioned, what did the plugs look like? You mention you had them out.
Do you know the truck's history? Have the plugs been changed? More details please.

 

Plugs and other cylinders looked as you'd expect. They were stock plugs on a 160k vehicle. #6 diode was about gone. The rest (1-5) looked uniform and normal.
#6 was a hair cleaner than the rest but that's about it.
Borescope photo was taken after 24-48hrs of sitting.
4runner had regular oil changes, single family owned, after borescope replaced all plugs with Denso

 

160k on factory plugs when the change interval is 30k? I hope your catalytic converters haven't been cooked by all the unburned fuel from misfires.

 

Lol guess I should've bought it from them years ago then?

I've owned this for a month or so. So yeah, doing all the maintenance that needs to be done and anything else I find along the way.

The plugs were half NGK/Denso, as they are installed stock, so whether they were actually the stock plugs or just the same 3 x 3 who knows. I do assume they were stock after seeing the wear. I pulled the carfax and the family kept up with regular oil changes since new. No rotten egg smells from cooked cats yet but only time will tell.

It's been driven less than 1k since purchase.

 

They are so reliable it’s not uncommon for people to just put gas in them and go….. for VERY long periods of time. Honestly I would venture to say 5% of the Toyota owners do the actual maintenance called for. Nobody I know changes trans and differential oils. Everybody just cranks and runs and drives them fill something happens usually well into the 150,000+ mile range. I’ve seen people with 250,000 on stock plugs. They almost always come in with #6 coil dead and #6 plug totally burnt out. Most folks run them till they won’t run anymore. Maintenance on a Toyota is something most folks don’t think about.

 

@Airdam oh I'm right there with you. I've made videos on IG for friends about greasing driveshafts and general maintenance. One of my buddies has a 5th gen with 140k on it. We were lifting my 5th gen a couple years ago and I said I needed to grease the shafts while I was doing the lift. He said.... what do you mean? He had never greased the driveshafts in 140k lol. I tried to explain I do mine every oil change and he just chuckled and said I was doing too much.

2 months later I get a text. Its his 4r on the side of the road and the rear shaft hanging down lol. Some lessons are learned the hard way.

 

I would think more on the lines of worn piston rings allowing oil blow by on the piston……if there is no water/oil mixture or weird overheating.