97 explorer 4.0 sohc code P420,301,306

[olraz]

First car was losing power at idle then at slow speeds. 1s codes were P420 P306 Cat Conv I know is bad but was holding off changin it out.

1st thought was head gasket since I was losing antifreeze somewhere without any leaks detected.
Some white smoke but knot a lot only at 1st start up.

Changed the coil pack nothing happened.
#6 Cylinder is clean other plugs are carboned but look fine. Thought the antifreeze was cleaning the plug on #6.

Tried Bar's Head Gasket sealer. now getting P301 code.

Any suggestions. This my son's car for college and I don't want to send it back to him with bad head gasket. Thought the Bar's would temp fix the problem then I could make a decision to fix or get rid of car. Doesn't seem like head gasket problem, at least not now.
Thought about the o2 sensor but don't know hwere it is... I've looked for it and cannot find it from the top of the car. Liooked both side of engine near manifold area but nothing.

Is there a manual or parts schematic on line anywhere I can use?

Anyone have further suggestions that I maight try?


Thank you
Lar

 

[Tbars4]

...i would venture to say it is the head gasket...when you shut it off and it sits for awhile, it leaks into the cylinders...thats why you get the white smoke at start up...
code 306 is cylinder 6 misfire, code 301 is cylinder 1 misfire...you were correct with the antifreeze cleaning the number 6 spark plug...all the signs lead to head gasket...
...on a good note, this tends to be a common item usually once in the explorer's lifetime...there are a few write ups on head gasket replacement on here, i believe they are in the under the hood section...

 

[olraz]

hoping head gasket sealer will give a temp fix

I used Bar's head gasket sealer hoping to get a quick temp fix for about 15k miles minimum.

I want to fix the Cat Convert 1st. I'm looking for best kit out there that will ease the pain of putting it on myself.

I don't have a alot of room but I do have alot of time...

I've been quoted $700. I saw somewhere as long as an OEM kit is used it is easy with no cutting or welding... Just hangers are the most difficult part and getting out from underneather the car becasue it has to be lifted high enough...

I think it was Flowmaster was the best unit for the Explorer?

 

[cjones101812]

you should repair the misfires first.

the misfires may ruin your new cat also. cats don't like misfires or coolant. i had one lady come in with a bad misfire and her cat was melting (yes, literally melting, metal dripping on the shop floor. she didn't know you needed to replace spark plugs occassionally).


have you checked the engine compress??

 

[olraz]

No, haven't checked compression yet. I changed plugs beginning summer. At that time I had no problems other than knowing I needed a new cat. I didn't realize the cat was so important at time. I thought it was just an emissions default. But apparently when it is not working, it throws everything off.
I'm dealing with the possible head gasket now and want to tackle the cat.

How difficult is it to replace a cat? What brands are easier to install than others. I read somewhere the Flowmaster? Apparenly there are different types that require cutting or welding and others that require nothing but to rebolt and re-hang...

 

[Space Truckin']

Antifreeze can also corrupt the 02 sensor and may be what caused the code P420. This code does not automatically mean the converter is bad. Fix the antifreeze leak first, then the misfire, and check the 02 sensor operation last. The P420 code may go away without replacing the converter if the other problems are solved first.

I came across this while doing a search. I know it has been a month but I hope the help is better late than never… Did you solve the problem already?