CEL, 4LO, Trac off. Code P0308

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jeep2cruiser

jeep2cruiser

Joined
Jun 20, 2019
Messages
174
Location
Houston, TX
Hey fellas!

Getting a misfire on cylinder 8. CEL, 4LO and Trac off on the cluster. Code is P0308 which is misfire on cylinder 8. I’m thinking coil pack or spark plug? I know this was an a common issue on the old 4.7 but haven’t seen anything on it on the 5.7. Thoughts?

-Pat
 
#8 is passenger side rear. How many miles On the plugs? Do you have the tools to pull the plug and take a look?
 
Sandroad said:
#8 is passenger side rear. How many miles On the plugs? Do you have the tools to pull the plug and take a look?
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I don’t have a socket long enough sadly, but that will be my next guess. I went ahead and swapped the coil pack between 6 & 8. Definitely not the coil pack. 51k on a 2014.
 
I also had a flowmaster muffler on there for a bit, just had the stock muffler put back on this week. Noticed a lower idle speed since then. Chances that the muffler swap messed with the O2 sensor, thus causing a misfire?
 
I had this exact thing happen. It was the spark plug. Spark plug would not come out at first and the dealer initially said they might have to remove the head. Luckily it they were able to get it out.
 
kcjaz said:
I had this exact thing happen. It was the spark plug. Spark plug would not come out at first and the dealer initially said they might have to remove the head. Luckily it they were able to get it out.
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ok cool. Looks like an Autozone trip is in my future.
 
Someone was saying the stock tool kit has a tool to remove spark plugs??
 
Ok. So the issue is intermittent, usually happens after I start up the car for the second time in the day. I clear the code and it's gone for the rest of the drive. I ran my tank basically dry and put some new gas in (my thought being maybe bad gas). I start up and it runs smooth. But then it came back last night... So my thoughts are maybe O2 sensors, something in the evap system, a wiring issue on cylinder 8 or maybe I just got some s*** gas. I know a common issue is the soy based wiring insulation underneath the intake manifold attracts rodents so maybe it's that?

Again, thoughts anyone?
 
Just wanted to check to see if you ever made any more progress on this issue? Had the exact thing happen this afternoon. Like to the tee. First the CEL was flashing, so I shut it off and restarted and the next time the CEL was just on solid. Scanned it and it was the same P0308 code. Cleared the code and drove home without issue.

Due to the myriad of seemingly unrelated circuits, My normal assumption would be a ground issue, rodent damage or just the stars misaligned on the Land Cruiser front i.e. no real issue at all and just transient electrical gremlins…
 
I just had same issue while my wife was driving. She did not notice anything abnormal other than the lights mentioned here. Ran the code check and get P0308. I reset it and will drive it myself to see if I can replicate before I do anything else…
 
dcs111 said:
I just had same issue while my wife was driving. She did not notice anything abnormal other than the lights mentioned here. Ran the code check and get P0308. I reset it and will drive it myself to see if I can replicate before I do anything else…
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update to the P0308 code - I drove the truck for about a week and the P0308 tended to occur at cold startup and would generally remedy itself within a few seconds. Towards the end of that week, the problem seemed to be more persistent and would occur around both warm and cold starts. I started to swap the coils to determine if that was the issue, but ran out of time... so off to the local Toyota dealer. I was not exactly sure what steps they took to determine, but dealer maintenance rep called after having the truck a couple hours and noted the #8 coil was bad and suggested to also replace the #8 plug as it was fouled... They also went ahead with induction/injector cleanings. Truck was returned to me next day and started up fine - no codes/ no misfires... two days later and I am getting P0308 again. One of a few things is happening and I am not sure exactly what I want to do:

- Dealer did not troubleshoot to the actual problem (and just replaced coil/plug)
- Dealer replaced bad coil with another bad coil (doubtful)
- Dealer replaced bad coil with good coil, but truck has multiple issues with #8 cylinder (seems unlikely)
- Dealer did not actually replace coil and just took my $

I called to speak with the service rep this morning and he was off and so spoke with service manager (who i am not a fan of). I asked him to check with tech to determine what steps were taken to troubleshoot the misfire issue - after "speaking with the tech" he noted that the #8 plug was moved to #6 cylinder and the #8 coil was moved to the #4 cylinder. Upon starting the misfire followed both the plug and coil... i suspect that to be suspect at best and I say that because when I initially spoke with the service rep prior to dealer performing maintenance, he said the coil was bad and that the plug "should be replaced" because it was fouled... a slight nuance to the story between the two recounts...

I guess I am going to have to troubleshoot this myself in order to figure it out. Truck has 139k and I manage all maintenance according to Toyota specified... no obvious oil or coolant issues... no apparent issues with the ignition harness at the coils or anywhere else... no recent maintenance or disturbances to the motor.

I am speculating, but wonder if i really only had a fouled plug which could have been caused by an injector issue (which has yet to be troubleshot and discovered)... e.g. dealer just replaced stuff and really did not attempt to fix the problem? or worse... could my coil/plug issue cause what could now be a head gasket issue (seems really unlikely)?

I appreciate any thoughts here!
 
jeep2cruiser said:
Ok. So the issue is intermittent, usually happens after I start up the car for the second time in the day. I clear the code and it's gone for the rest of the drive. I ran my tank basically dry and put some new gas in (my thought being maybe bad gas). I start up and it runs smooth. But then it came back last night... So my thoughts are maybe O2 sensors, something in the evap system, a wiring issue on cylinder 8 or maybe I just got some s*** gas. I know a common issue is the soy based wiring insulation underneath the intake manifold attracts rodents so maybe it's that?

Again, thoughts anyone?
Click to expand...
I am curious what was the resolution for your issue? thx!
 
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