P0455 Problems Fixed, Now its P0306 #6 Misfire

jsc7002 · **Posted:** Tue Jun 09, 2009 11:20 am

My check engine light has been on for a little while and it has been the P0455 and I havent had any problems with it until now. I was driving earlier today and I thought it was going to die when I pulled onto the road. And it seemed like it shifted a little late and it sounds like it is idling a little rough also.

any ideas what would be causing this??

tommudd · **Posted:** Tue Jun 09, 2009 11:38 am

0455 leak detected in the evaporative system, have you checked any of the lines or anything lately?

tjkj2002 · **Posted:** Tue Jun 09, 2009 12:39 pm

EVAP codes do not effect engine operation,purely emission related(in 99% of all cases).

BennyMigs · **Posted:** Tue Jun 09, 2009 1:06 pm

I had same problem last week check your gas cap. Here is the link to the thread only a few down from your.
http://www.lostjeeps.com/forum/phpBB3/vie ... hp?t=43830

jsc7002 · **Posted:** Tue Jun 09, 2009 1:52 pm

tjkj2002 wrote:

EVAP codes do not effect engine operation,purely emission related(in 99% of all cases).

what do you think it is?

BennyMigs wrote:

I had same problem last week check your gas cap. Here is the link to the thread only a few down from your.
http://www.lostjeeps.com/forum/phpBB3/vie ... hp?t=43830

its not the gas cap, I know for sure. I crawled under the KJ and I found 2 hoses that were cracked and I replaced one already but I will have to run to town to get the other hose.

also I noticed while I was driving the check engine light was flashing, Ive never seen it actually flash, normally it just comes on and stays lit

tjkj2002 · **Posted:** Tue Jun 09, 2009 3:10 pm

jsc7002 wrote:

tjkj2002 wrote:

EVAP codes do not effect engine operation,purely emission related(in 99% of all cases).

what do you think it is?

BennyMigs wrote:

I had same problem last week check your gas cap. Here is the link to the thread only a few down from your.
http://www.lostjeeps.com/forum/phpBB3/vie ... hp?t=43830

its not the gas cap, I know for sure. I crawled under the KJ and I found 2 hoses that were cracked and I replaced one already but I will have to run to town to get the other hose.

also I noticed while I was driving the check engine light was flashing, Ive never seen it actually flash, normally it just comes on and stays lit

Flashing check engine light is a serious misfire or other serious engine malfunction.If the light is flashing shut the engine down ASAP before engine damage occurs(50/50 shot there),a steady "on" MIL is not a serious problem that will lead to damage.

BennyMigs · **Posted:** Tue Jun 09, 2009 3:28 pm

YA I would not start it till all the lines are replaced.

tjkj2002 · **Posted:** Tue Jun 09, 2009 5:44 pm

BennyMigs wrote:

YA I would not start it till all the lines are replaced.

EVAP codes will not make the MIL flash,only misfire/knock codes can.

Prospect62 · **Posted:** Wed Jun 10, 2009 12:53 am

tjkj2002 wrote:

BennyMigs wrote:

YA I would not start it till all the lines are replaced.

EVAP codes will not make the MIL flash,only misfire/knock codes can.

Yeah, sounds like you might have something else going on besides the 0455. I would still replace those cracked rubber EVAP lines...but read those codes again and see what else comes up, if anything.

jsc7002 · **Posted:** Wed Jun 10, 2009 2:43 pm

okay I replaced the lines and took off the gas cap and put it back on and then I disconnected the battery but when I got in I tested it and no codes came up so I started it and drove it around the block and no check engine light came on but it still is running funny, under acceleration it doesnt really just go it just kind of putters and slowly goes faster.

now what is it??

jsc7002 · **Posted:** Wed Jun 10, 2009 2:49 pm

yellocoyote wrote:

Have the symptoms been around for more than one tank of gas? You getting fuel at the same place all the time? I wonder if it's bad fuel...

thats kind of what I was thinking. I fill up all over the place but I usually only use certain stations that I know and like, which if it is bad gas thats no good because I still have a full tank, I only drove it 20 miles after filling up.

any other ideas?? or do I just need to suck it up and drain it? and what about the flashing CEL?

jsc7002 · **Posted:** Wed Jun 10, 2009 10:31 pm

I was talking to a local mechanic and he said that since I cleared the P0455 by disconnecting the battery it would have cleared all of the codes and he said I just need to get the motor/ computer to cycle and he said I can do that by going 60mph slow down speed back up to 60 slow down and speed back up to 60 and it should complete its cycle and look for anything wrong. So I did it and nothing came up so I keep doing it, I think I did it about 5 times and then I just got on the highway so I could really get it up higher and I went about 1 miles going about 70mph and got out to check some of the tubes and it sounded like it was running right so I got back on the highway to head home and it was running like nothing had happened, it sounded right and shifted right and accelerated right. So I dont know what it was but it seems to be fixed.

Edvalencia · **Posted:** Thu Jun 11, 2009 11:09 am

jsc7002 wrote:

I was talking to a local mechanic and he said that since I cleared the P0455 by disconnecting the battery it would have cleared all of the codes and he said I just need to get the motor/ computer to cycle and he said I can do that by going 60mph slow down speed back up to 60 slow down and speed back up to 60 and it should complete its cycle and look for anything wrong. So I did it and nothing came up so I keep doing it, I think I did it about 5 times and then I just got on the highway so I could really get it up higher and I went about 1 miles going about 70mph and got out to check some of the tubes and it sounded like it was running right so I got back on the highway to head home and it was running like nothing had happened, it sounded right and shifted right and accelerated right. So I dont know what it was but it seems to be fixed.

While I was getting different codes (p0123 and p1299) my KJ was doing something very similar to what you describe. After I disconnected the battery, it ran fine for a couple of weeks, then it started doing it again and got progressively worse to the point where it would just stall. I narrowed the problem down to the Throttle Position Sensor, which took all of 5 minutes to change. If you get the CEL again, make sure you get all the codes read before disconnecting the battery.

jsc7002 · **Posted:** Thu Jun 11, 2009 11:55 am

okay I got in it today and the CEL came back flashing and I checked it as P0306 Cylinder 6 Misfire Detected, what do I need to do to fix it?

thanks

jsc7002 · **Posted:** Thu Jun 11, 2009 1:53 pm

I pulled the #6 coil pak and then the spark plug to check it and they both looked clean so then I also pulled the one in front of it #4 I believe and it was oily.

Also the #4 coil pack and spark plug not only came out with a slight drip of oil on them but the little rubber piece on the bottom of the coil pack is loose

#6 and #4 coil packs and spark plugs

#4 Spark Plug

#6 Spark Plug

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

Was searching the forums and came across this old post...

To the OP... did you ever get this issue resolved? I'm having similar issues on my wifes '03 3.7 KJ. It's had the CEL of P0306 for a while now... I've changed the Coil Pack (#6), changed plugs, replaced the Pass Valve Cover gasket to fix the oil leak, Checked the engine Compression and all cylinders are w/in spec, replaced busted Vacuum lines on both Cylinder sides to Air Intake ... (I have not changed any of the O2 Sensors, Cat Converters, Fuel Injectors) ... Up until yesterday the CEL was constantly ON. Yesterday it started sputtering when at a stop and the CEL was flashing. She drive it home ~ 2 miles.

When at home I pulled the Throttle Body and Idle Air Control Valve off to clean them and remove all the carbon. Checked all the vacuum lines in the Engine bay and they were all in good shape. I cleared the CEL codes and took it for a drive. It idled much better and ran fine. Only drove it around for about 2 miles and did a lot of sudden stops, quick acceleration, sudden stops type of cycles. All was fine. No stumbling or stuttering.

One other thing I've noticed is that there is an unusual amount of white smoke coming out the tailpipe on the KJ especially when it's cold outside. Not the normal slight white puffs until it warms, but lots of white smoke. She also looses a bit of coolant and it's nowhere to be found in the engine bay. No leaks f/the radiator, water pump or thermostat housing. I'm really concerned about a leaking or blown head gasket. Wouldn't that reveal itself on the Compression Test I ran? I'm at a loss... don't want my wife to be driving around in a ticking time bomb.

Oh, and the KJ has 124k miles on the Odometer, Auto Tranny, 4x4.

Thanks...

P0455 Problems Fixed, Now its P0306 #6 Misfire

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