Cylinder Misfire/Leaking Coolant

Hey guys!

I'm new to tacomaworld so sorry if this topic is repetitive but I'm having some issues with my 2006 6 cylinder Tacoma with 215K mileage and needed some advice.

So the check engine light came on the other day and stayed on (will not reset, code keeps coming back) the code is P0303. I've changed the spark plugs all around and the issue went away for a few months. I then swapped the coil packs with another cylinder hoping there would be a different code. Sure enough it was still the same code. I'm swapping out the fuel injector tonight but wondering if anyone had other thoughts on the issue.

I checked the compression beforehand and these were the results:
Cylinder 1: 208
Cylinder 3: 195
Cylinder 5: 200
Cylinder 2: 130*
Cylinder 4: 198
Cylinder 6: 208

Cylinder 2 is surprisingly low but all the others seemed fine. I have had a coolant leak as well with no visual signs, oil is clean, no white smoke or sweet smell from exhaust. I'm wondering if I have a head gasket leak or if this issue could be related to my cylinder 3 misfire.

Note: My truck overheated about a year ago and the water pump and thermostat was replaced by a local mechanic and has been fine since. The coolant leak has been around for a few months now and the cylinder misfire was more recent. Also when I recently pulled the cylinder 3 spark plug I noticed black soot over the tip of the plug but nothing else. See the photos for reference compared to the other plugs

Any help would be appreciated on what you guys think.
Thanks!
-Mitch

 

My thoughts.....

Iridiums give no gain in the 1GR-FE engine. Iridiums are known to cause running issues in some of these engines.

The plug on the right appears to be extremely clean, almost like the insulator has been steam cleaned.

You had an overheat situation about a year ago which required replacement of H2O pump and T-stat. Overheat is a leading cause of head gasket fails.

You know of a coolant leak. Is the coolant leak visually evident?

Also, your mileage is reaching a point where serious engine issues can arise, especially when aggravated by a problem history.

Suspect you have a head gasket failure around Cyl #2.
Suggest to run a pressure test on the Coolant system and a Leak Down test on the cylinders, specifically cyl #2.
Then you will likely have the evidence to firmly support a diagnosis of the Head Gasket.

Good Luck

 

^ This. Good Luck