Missfire #4 & #6

[kid0ry]

I know there are a few different threads out there that relate to my issues, but i wanted to start this new thread to get some specificity.

1999 Explorer V6 4.0L OHV
I was getting a misfire code p0306. I replaced plugs and wires and checked compression. Reset ECU and the code still came up. I then bought a new coil pack form clark's (garbage cheap prices and products). I installed it and it ran worse! It felt like the engine was gonna snap off of the motor mounts... So I put the stock coil back in and (being a starving college student) bought and replaced only the 6th cylinder fuel injector. Upon registering all the sensors the check engine light came on again. This time it read p0304. I hadn't had time to poke around down there for some time. But when I finally did I read code again, p0304 came up like last time. But p0306 came up again too! Oh, I'm also slowly losing coolant...
There are many things that come to mind. Im pretty sure i don't have a vacuum leak, but I'm going to pull all my plugs and check em and run another compression test. I'm also going to run an ohm test on the coil. I also read a little about COP boots? I'm not a mechanic in the least. This is my first time working this in depth with an engine, aside from basic tune up stuff. What and where is a COP boot?

Anyways if all this checks out and I'm still getting misfires I will move lower and replace ALL the fuel injectors this time.

Until then I would like to say thank you in advance for taking time to read this and for any suggestions and guidance.

My next post will explain all results (with pictures if need be)

 

[joe doe]

dont go pulling the injectors ,thats rarely ever the issue .
if your slowly loosing coolant then i first suspect your head gaskets to be leaking unless you find an obvious leak somewhere else .

get yourself a good light and look thru the wheel well at the engine block .see if you see any leaking antifreeze or the green tint trail it will leave there .

also sounds like you got some misfires going on .your code is a cyl number 4 misfire and a cyl number 6 misfire .

pull both plugs and check their condition .look closely at the ceramic portion of the plug(the insulator) (around the firing pin)and be sure its not cracked .
a cracked insulator is a indicator of a head crack .
this could explain the coolant loss as well .if coolant is getting in those cylinders it will continue to ruin plugs and crack the insulators .(been there done that)
head cracks are common on there engines .

good luck and report back your findings .

 

[SoNic67]

Probably the coolant gets in the heads and shorts the plugs. Remove the plugs an see if they look "wet".
Also, excessive white smoke at the exhaust pipe means water vapors = antifreeze being sucked into heads.

 

[kid0ry]

p0304, p0306, p0174bank2

My long overdue look underneath the hood finally happened today. So, the same misfire is still present, along with another code that popped up today. It read p0304, p0306, and p0174bank2. As I stated before I replaced only the one injector on #6 and still got the misfire code. When p0304 popped up I pulled the plug to inspect it and it was pretty wet. I thought it was oil at first but with a closer sniff I realized it was fuel. I checked compression and all the cylinders are all within 20psi of each other (145-165). I don't think there's a cracked head or a blown gasket if I'm pulling those numbers.

As for the p0174bank2 code. In the Haynes manual it says that it's a bad O2 sensor (right side). I also read that it might be a dirty or bad MAF sensor. I hit the MAF sensor with some contact cleaner. That didn't really help at all. I also read that it would be beneficial to check continuity. Haven't done it yet.

The real question is what would be causing this misfire? I guess my first step would be to replace the O2 sensor(s). I won't be able to do it until next week. I'll check my fuel system after that. The filter got replaced two years ago. Maybe I'll check the fuel pressure and all the lines.
Any advice would be much appreciated.

 

[drdoom]

Have you tested resistance of the coil pack?

 

[bobflood]

My long overdue look underneath the hood finally happened today. So, the same misfire is still present, along with another code that popped up today. It read p0304, p0306, and p0174bank2. As I stated before I replaced only the one injector on #6 and still got the misfire code. When p0304 popped up I pulled the plug to inspect it and it was pretty wet. I thought it was oil at first but with a closer sniff I realized it was fuel. I checked compression and all the cylinders are all within 20psi of each other (145-165). I don't think there's a cracked head or a blown gasket if I'm pulling those numbers.

As for the p0174bank2 code. In the Haynes manual it says that it's a bad O2 sensor (right side). I also read that it might be a dirty or bad MAF sensor. I hit the MAF sensor with some contact cleaner. That didn't really help at all. I also read that it would be beneficial to check continuity. Haven't done it yet.

The real question is what would be causing this misfire? I guess my first step would be to replace the O2 sensor(s). I won't be able to do it until next week. I'll check my fuel system after that. The filter got replaced two years ago. Maybe I'll check the fuel pressure and all the lines.
Any advice would be much appreciated.

Premature to replace O2 sensors; you don't really know if one is bad until you get the misfires fixed. As noted, 0304 and 0306 are misfires on cylinders #4 and #6. They are on the driver's side of the engine; that is also identified as "bank 2." Most will call that the "left" side of the engine - it's only the right side if you are standing at the front looking in! That is one of the reasons most folks on these forums talk about driver's side and passenger's side when referring to where things are.

For codes that are identified by "bank 1" or "bank 2" - bank 1 is always the cylinder bank with the #1 cylinder in it. For all our Ford Explorer engines, cylinder #1 is the front cylinder on the passenger side - therefore, "bank 1" is on the passanger side.

Thus endth the lesson.

 

[kid0ry]

I did test the coil when I got new plugs and wires. I don't have the piece of paper with all my findings, but from what I recall the coil pack was fine. (I'll test again while troubleshooting next week.) I did however buy a brand new coil pack as well when I replaced the plugs and wires. I mounted the new one and it ran even crappier than the old one (I bought it from Clark's discount auto part). So I threw the old one back on. I'm going to buy a new one from a reputable place such as NAPA or Pep Boys.

Thanks Bobflood, for the lesson. I will address those misfires before anything else. I'm going to start with the fuel system first. Hopefully I find some answers while troubleshooting next week. I'll update with my findings.

Any other suggestions?

 

[my98nnj]

I'm going to start with the fuel system first. Hopefully I find some answers while troubleshooting next week. I'll update with my findings.

Any other suggestions?

If your plugs are wet with fuel then fuel isn't your problem.
Your missing the spark to ignite the fuel.
Check plugs, wires and the coil.
Make sure the wires are on the coil correctly, refer to the diagram in the above post regarding cylinder position and it's relative spot on the coil.

 

[joe doe]

dont replace the 02 sensor just yet ,thats rarely ever the issue when that code is thrown .most likely is a intake gasket leak or upper plenum oring leak .very common on these engines .
i told you above how to check your plugs .you need to pull the ones that are misfiring and check them as i have explained .
the fact your losing coolant only leads me to believe i am correct .

pull the plugs ,look for cracked insulators at the firing pin .if its cracked you got a head crack into that cylinder or a leaking head gasket into that cylinder .

check the plugs and report back .

ps- do not replace the injectors either ,thats rarely ever the issue as well .

 

[kid0ry]

dont replace the 02 sensor just yet ,thats rarely ever the issue when that code is thrown .most likely is a intake gasket leak or upper plenum oring leak .very common on these engines .
i told you above how to check your plugs .you need to pull the ones that are misfiring and check them as i have explained .
the fact your losing coolant only leads me to believe i am correct .

pull the plugs ,look for cracked insulators at the firing pin .if its cracked you got a head crack into that cylinder or a leaking head gasket into that cylinder .

check the plugs and report back .

ps- do not replace the injectors either ,thats rarely ever the issue as well .

I checked all the plugs when I did the compression test. There were no cracks and they all seemed fine, with the exception of # 4 which was doused in fuel. No cracks. After I put the plugs back in, I made sure that each one was getting a spark via pulling wires in and out of the coil. They were all getting spark.