Code P306

Maximum Carnage · **Posted:** Tue Nov 09, 2010 11:10 am

I keep getting this P306 code for a few days & I can't figure out how to solve for it. Spark plus have been changed W/proper NGK plug and gap, I switched the coil pack in cylinder 6 W/cylinder 2 and I still got the same results, darn code is back. What next?

liquidxit2 · **Posted:** Tue Nov 09, 2010 1:33 pm

The only other things I can think of that would cause a misfire are the fuel system, combustion chamber (piston and valve issues), the timing chain (causing bad engine timing) or the PCM. Other then that Im at a loss. You could try running PIDs or data while driving and record it to see whats happening when it misfires.

tjkj2002 · **Posted:** Tue Nov 09, 2010 1:42 pm

Maximum Carnage wrote:

I keep getting this P306 code for a few days & I can't figure out how to solve for it. Spark plus have been changed W/proper NGK plug and gap, I switched the coil pack in cylinder 6 W/cylinder 2 and I still got the same results, darn code is back. What next?

Time to pull the valve cover and check the "rockers" on #6,to bad #6 is on the hard side with those dang hard line heater hoses.

Also like stated you could have a PCM issue with either the injector or coil,if that is the case a whole new PCM is required and this type of issue is not unheard of.A easy test is to get the engine to the point where it is misfiring,then with the engine running unplug the coil connector,if it get's worse the coil and coil driver in the PCM is good.Then after that unplug the injector connector,if it get's worse it's not the injector or injector driver in the PCM.In either of those 2 tests if the engine does not misfire worse(or bog down,you'll know it or not) then that perticular component is at fault(injector or coil).If it is a injector you can try and have a fuel system cleaning that ties directly into the fuel line to get it cleaned(dirty injectors is a common problem),I have had some success by doing that and saved the customer lots of $$$.If none of that gets you any closer then it is mechanical and under that valve cover.

Maximum Carnage · **Posted:** Tue Nov 09, 2010 2:50 pm

liquidxit2 wrote:

The only other things I can think of that would cause a misfire are the fuel system, combustion chamber (piston and valve issues), the timing chain (causing bad engine timing) or the PCM. Other then that Im at a loss. You could try running PIDs or data while driving and record it to see whats happening when it misfires.

I'm lost what is the PIDs ??
I did try Seafoam and I got the hug cloud of white smoke but after unplugging the battery for a reset I eventually got the same code.

Maximum Carnage · **Posted:** Tue Nov 09, 2010 2:58 pm

tjkj2002 wrote:

A easy test is to get the engine to the point where it is misfiring,then with the engine running unplug the coil connector,if it get's worse the coil and coil driver in the PCM is good.Then after that unplug the injector connector,if it get's worse it's not the injector or injector driver in the PCM.In either of those 2 tests if the engine does not misfire worse(or bog down,you'll know it or not) then that perticular component is at fault(injector or coil).If it is a injector you can try and have a fuel system cleaning that ties directly into the fuel line to get it cleaned(dirty injectors is a common problem),I have had some success by doing that and saved the customer lots of $$$.If none of that gets you any closer then it is mechanical and under that valve cover.

I'll try this, I just don't want to have to pull the valve cover and get too much into the mechanical of things.
What are your thoughts on a vacuum leak?

tjkj2002 · **Posted:** Tue Nov 09, 2010 4:04 pm

Maximum Carnage wrote:

tjkj2002 wrote:

A easy test is to get the engine to the point where it is misfiring,then with the engine running unplug the coil connector,if it get's worse the coil and coil driver in the PCM is good.Then after that unplug the injector connector,if it get's worse it's not the injector or injector driver in the PCM.In either of those 2 tests if the engine does not misfire worse(or bog down,you'll know it or not) then that perticular component is at fault(injector or coil).If it is a injector you can try and have a fuel system cleaning that ties directly into the fuel line to get it cleaned(dirty injectors is a common problem),I have had some success by doing that and saved the customer lots of $$$.If none of that gets you any closer then it is mechanical and under that valve cover.

I'll try this, I just don't want to have to pull the valve cover and get too much into the mechanical of things.
What are your thoughts on a vacuum leak?

A vacuum leak will not cause a misfire.

liquidxit2 · **Posted:** Tue Nov 09, 2010 4:24 pm

Maximum Carnage wrote:

liquidxit2 wrote:

The only other things I can think of that would cause a misfire are the fuel system, combustion chamber (piston and valve issues), the timing chain (causing bad engine timing) or the PCM. Other then that Im at a loss. You could try running PIDs or data while driving and record it to see whats happening when it misfires.

I'm lost what is the PIDs ??
I did try Seafoam and I got the hug cloud of white smoke but after unplugging the battery for a reset I eventually got the same code.

PIDs are parameter identifiers, basically a ford term I used for data streams from sensors. Basically when we had a dirveability issue we set a scanner (NGS or WDS) to monitor several sensors data streams and either on the lift or out on the road recreate the problem. When the problem occurs you mark the time and when you get back to the shop you look at the data streams around the time and it can tell you whats going on. Granted its never 100%, and requires tools that range in the $1.5k + ranged to do (advanced PIDs arent available to lower end scanners due to manufacturers wanting to keep an edge over small shops and shade tree mechanics). When I was a tech if I got a ticket on your vehicle I would make a list of systems and subsystems to watch and do what I said above. Outside of that TJKJ's Idea is what will help you self diag the problem.

Maximum Carnage · **Posted:** Tue Nov 09, 2010 9:10 pm

On my drive home, the check engine light kept blinking and I was getting the sputting engine syndrome but I was still able to drive at normal speed. After about 4 miles I pulled over turned it off let it sit for maybe a minute started her up again and drove home with out the syndrome but the check engine light is now constant on.
My question is if something is wrong (code p306) what would make it work periodically?

Maximum Carnage · **Posted:** Sun Nov 21, 2010 5:30 pm

Does anyone have the instructions on how to replace the cylinder head gasket? It seems a blown head gasket is the issue, hope the head it's self is not cracked/warped...

Maximum Carnage · **Posted:** Sun Nov 21, 2010 10:36 pm

I've done a gasket fix before but the book says the timing belt has to be removed?? Any help?

tjkj2002 · **Posted:** Sun Nov 21, 2010 10:39 pm

Maximum Carnage wrote:

I've done a gasket fix before but the book says the timing belt has to be removed?? Any help?

The timing chain needs to come off partly.Timing belts are for the 2.4 gassers and CRD's only thank g o d.

Maximum Carnage · **Posted:** Wed Nov 24, 2010 5:55 pm

It completely died on me on Monday on my way home. I had it towed to a friend’s house. I don't have the time to fix it myself. It sounds like it's going to be more than just a blown gasket

... I'll keep you posted.

redsnake · **Joined:** Fri Nov 26, 2010 9:51 pm **Posts:** 41

I'm new to this forum but my wife's '03 KJ is having similar problems. I've replaced the plugs and even the coil pack on the #6 cylinder. The check engine light hasn't come back on... but it's only been 1 day. It just seems like it could be one (or several) of many things causing this and I'm not sure what exactly.

I'll keep following this and update if I solve the issue on my wife's Libby. Good luck and keep up posted.

Maximum Carnage · **Posted:** Mon Nov 29, 2010 9:30 pm

After towing to my friends house, he did a few tests and started it up but did not sound too good. Some metal clanking around the engine shut her off and got an additional code P0203. We surely knew we had to open her up. We remove the engine and over the weekend he disassembled the engine to find out a rocker was floating around; seems that an adjuster gave.

I will go to an engine shop sometime Tue or Wed to get prices on all parts.

Code P306

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