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Discussion Starter · #1 ·
Hey all,

Been a big follower of this forum since I bought my first taco back in 2009, you guys have been such an awesome resource when it comes to finding answers to a lot of FAQ's- so appreciative of this community! This last weekend I was out camping and did a little bit of wheeling one of the days, nothing crazy but something worth mentioning. I did a fair amount of highway / forest service road driving (probably 60+ miles) before heading back to town.

On my way back I was climbing a moderate grade pass and just as I crested it I could feel something was not right with my truck. As soon as I turned my music and AC off to see if I could hear anything, I saw black smoke come up from under my hood and could feel the motor was running rough. I immediately pulled over and turned the truck off to see what was going on and was not able to place where the leak was coming from. It definitely looked and smelled like motor oil.

I did briefly try start it back up after checking everything, which it did start and was idling rough so I immediately turned it back off. I decided to error on the side of caution and finally use the AAA membership I have had for decades and never used- not the happiest moment in my life :confused:

This truck has been nothing short of reliable for the entire time I have owned it. Its a 2005 double cab 4.0 V6 with about 213k miles, we have been on endless adventures since I bought it. A couple of summers ago I diagnosed that it had a bad head gasket- caught this early on before any damage occurred. Since then everything has been running super smooth. I checked valves, compression, etc. during this overhaul and everything was well within spec.

The most recent service I did was less than 500 miles ago. The amount of oil that I lost was very minimal, less than a quarter of a quart of oil between what tiny amount dripped on the highway, my driveway, and whats caught on my skid plate. At this point I have drained the oil and inspected for any metal shards or contamination, check coolant levels, and checked spark plugs which all of them looked fine.

I'm totally stumped as to where to look next.. I know I've had an 02 sensor/ exhaust leak issue that I have been needing to fix. When I plug in my code reader I am pulling a P0136, P0137, and P0306 code. I know the 36 and 37 code pertain to the 02 sensor / exhaust leak. The P0306 code appears to be a cylinder 6 misfire. I have not been able to test out coil packs or wires, but this still doesn't explain the oil coming out of wherever it came from.

When I go under the truck there is oil spread around since I was going highway speed. There is really only one spot that I am questioning that it could be coming from. I cant seem to find out what this connection is on any diagrams and would so appreciate any of your guys thoughts and input. This picture was taken under the drivers side looking up into the engine bay. I wasnt able to mark which spot I specifically am talking about, but it is in the center of where the light is shining and it dark grey. Looks pretty clean and like it may have had something attached to it, but I am far from a mechanic and am likely mistaken. Also am unsure which cylinder would be #6 as I have read that is is the last cylinder firing, not that they are in a particular order..can never know if what you read on the internet it true!

As of tonight I cleared the codes, replaced the oil+ filter, and re checked my coolant levels. Went to attempt to start it and it did fire up, but it was running so incredibly rough I shut it off after a couple of seconds. At this point I don't know where to start looking to diagnose what's going on and am hoping to get some input from my fellow gear heads ⚙;)

Thanks everyone!
 

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Mambeau / Admin
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AFAIK Cylinder #6 on a 1GR is the rearmost cylinder on the port (driver) side of the engine. See:

 
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Mambeau / Admin
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I'm completely lost in trying to understand the photo. Where underneath the truck were you when you took this photo? Coming underneath from the front? From the side (behind the driver-side front wheel)?
 

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Discussion Starter · #4 ·
I'm completely lost in trying to understand the photo. Where underneath the truck were you when you took this photo? Coming underneath from the front? From the side (behind the driver-side front wheel)?
Sorry I was not very specific with where I was when taking the photo haha. This was taken behind the drivers side front wheel looking up under the engine.
 

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Discussion Starter · #5 ·
AFAIK Cylinder #6 on a 1GR is the rearmost cylinder on the port (driver) side of the engine. See:

Thank you for the info! Would you recommend swapping coils with another cylinder to try and diagnose? How rough would it be running if it were not firing or misfiring in one cylinder?
 

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Mambeau / Admin
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If you swap the #6 coil with another cylinder and you start getting misfire codes for the other cylinder that would be a definite clue that it's the coil. If you can readily check the codes that would be a reasonable thing to try.
 
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