P0306 error code

[sblanck]

Greetings,

So I took my libby in because I was getting a P0306 code.
I put in new spark plugs and swapped coil packs but no change.
The mechanic says when he ran diagnostic on it plugs 2,4,6 were all reporting a misfire. So basically one side of my engine is out of whack. The mechanic thinks it electrical. He didn't mention injectors. Curious what folks here think?

Thanks

2004 Libby 3.7l engine

 

[kage860]

I would think the O2 sensor for that side of the engine is bad.

 

[sblanck]

Libby also had a leak from the valve cover so new gaskets both sides.
Mechanic replaced PCV valve and #6 injector and all codes cleared.
Most expensive part of this repair was having to capture the freon and then recharge due to the a/c system having to be unhooked to replace passenger side valve cover gasket.

 

[sblanck]

I would think the O2 sensor for that side of the engine is bad.

So do I replace both of the 02 sensors on that side?

 

[HoosierJeeper]

Likely upstream. The downstream ones just monitor catalytic performance, so they don't really have anything to do with how the engine runs. I think...

 

[sblanck]

Where are the upstream ones located? I googled and it just shows the two 02 sensors that are after the exhaust manifold.

 

[HoosierJeeper]

Those are the upstream ones, then the down stream ones are after the cats.
I'm not sure where they'd exactly be on yours, since every year of KJ seemed to have a different setup, but look between the exhaust manifolds and the cats.

 

[kage860]

If your codes stay clear with the work your mechanic did, it sounds like he found the problem already. Or is there still problems?

 

[JasonJ]

Libby also had a leak from the valve cover so new gaskets both sides.
Mechanic replaced PCV valve and #6 injector and all codes cleared.
Most expensive part of this repair was having to capture the freon and then recharge due to the a/c system having to be unhooked to replace passenger side valve cover gasket.

Yeah... having done this myself last year, discharging and disconnecting the A/C was NOT necessary... adds maybe 20 mins to the work time, but much simpler to work around the lines.

But I guess if the mechanic didn't know... or did not want to risk breaking something...