07 Rescue Green

I have an 07 JK with cold air intake and viper TB, getting P0301. I changed the plugs to Champions Double Platinum from the NGK's. After 30 miles or so, code is back. Wires are next, I was going to go with some performance wires (just to add color) but don't think the gain is worth the extra money so they will be stock. My question is, what should I look at after that if it persists? I've only had this rig for about 3 weeks, heater core went out and now this, not very happy so far. Thanks!!

ronjenx

Multi-cylinder misfire, and each individual cylinder misfire, all have nearly the same list of possible causes. It's probably the longest list in the troubleshooting charts.

Here it is:

P0300-P0306 CYLINDER MISFIRE
· When Monitored:
Any time the engine is running, and the adaptive numerator has been successfully updated.
· Set Condition:
The threshold to set the fault is application specific; it is tied to the level of misfire that will cause emissions to increase to 1.5 times the standard or in some cases 1%. It is always a two trip fault above the calibrated RPM. It takes 1 soft fail to set a malfunction and two trips to set the MIL. Three good trips to turn off the MIL.
[TABLE="class: MsoNormalTable"]
[TR]
[TD] [/TD]
[/TR]
[TR]
[TD="width: 452"] ASD RELAY OUTPUT CIRCUIT

[/TD]
[/TR]
[TR]
[TD="width: 452"] INJECTOR CONTROL CIRCUIT

[/TD]
[/TR]
[TR]
[TD="width: 452"] COIL CONTROL CIRCUIT

[/TD]
[/TR]
[TR]
[TD="width: 452"] IGNITION WIRE

[/TD]
[/TR]
[TR]
[TD="width: 452"] SPARK PLUG

[/TD]
[/TR]
[TR]
[TD="width: 452"] IGNITION COIL

[/TD]
[/TR]
[TR]
[TD="width: 452"] FUEL PUMP INLET STRAINER PLUGGED

[/TD]
[/TR]
[TR]
[TD="width: 452"] RESTRICTED FUEL SUPPLY LINE

[/TD]
[/TR]
[TR]
[TD="width: 452"] FUEL PUMP MODULE

[/TD]
[/TR]
[TR]
[TD="width: 452"] FUEL PRESSURE LEAK DOWN

[/TD]
[/TR]
[TR]
[TD="width: 452"] FUEL INJECTOR

[/TD]
[/TR]
[TR]
[TD="width: 452"] ENGINE MECHANICAL

[/TD]
[/TR]
[TR]
[TD="width: 452"] POWERTRAIN CONTROL MODULE (PCM)

[/TD]
[/TR]
[/TABLE]

VISUAL INSPECTION
NOTE: Anything that affects the speed of the crankshaft can cause a misfire DTC.
NOTE: When a Misfire is detected for a particular cylinder, the PCM will shut down that cylinder's Injector Control circuit.
Turn the ignition off.
- Visually inspect the engine for any of the following conditions.
- Worn serpentine belt
- Binding Engine-Driven accessories: A/C Compressor, P/S Pump, Water pump.
- Misalignment of the Water pump, P/S Pump and A/C Compressor pulleys
- Corroded PCM power and ground circuits.
- Improper CKP, CMP, MAP, and TP Sensor mounting
- Poor connector/terminal to component connection. i.e., CKP sensor, Fuel Injector, Ignition coil, etc.
- Vacuum leaks
- Restricted Air Induction system or Exhaust system.
- Internal engine component failures.



SPARK PLUG
Turn the ignition off.
Remove the Spark Plug.
Inspect the Spark Plug for the following conditions.
- Cracks
- Carbon Tracking
- Foreign Material
- Gap size out of specifications
- Loose or broken electrode
NOTE: Lightly tap the bottom of the spark plug on a solid surface. The electrode in the spark plug should not move.

ENGINE MECHANICAL
Check for any of the following conditions/mechanical problems.
ENGINE VACUUM - must be at least 13 inches in neutral
ENGINE VALVE TIMING - must be within specifications
ENGINE COMPRESSION - must be within specifications
ENGINE EXHAUST SYSTEM - must be free of any restrictions or leaks.
ENGINE PCV SYSTEM - must flow freely
TORQUE CONVERTER STALL SPEED - must be within specifications
POWER BRAKE BOOSTER - no internal vacuum leaks
FUEL - must be free of contamination
CAM LOBES - must not be worn excessively
CYLINDER LEAKAGE TEST - must be within specifications
VALVE SPRINGS - cannot be weak or broken

POWERTRAIN CONTROL MODULE (PCM)
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the related Sensor, Coil, Injector, and the Powertrain Control Module (PCM).
Look for any chafed, pierced, pinched, or partially broken wires.
Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the related Sensors, Coils, Injectors, and the Powertrain Control Module connectors.
Refer to any Technical Service Bulletins that may apply.

JK_Crawler

Try swapping the plug wire on cylinder 1 and 6, see if it follows. If not I wouldn't worry about the plug wires, They aren't the problem. Try swapping the coil on cylinders 1 and 6 and see if the misfire follows, if misfire doesn't move the ignition system is fine and there is something going on with that cylinder. Next move would be to perform a compression test and cylinder leak down test.

Good luck.

Also how many miles are on the jeep and was the CAI and TB already installed on the jeep when you bought it or were they on there already?

ronjenx

#6 plug wire won't reach #1 plug; way too short.
Swapping #1 and #6 coils will through the ignition out of time.

JK_Crawler

Use the next closest wire then.. Or go out and spend the money on a spark tester

07 Rescue Green

Thanks for the replies, I have 122k miles on her, the CAI and TB were already installed. From what I read on here, the wires should be changed at 102k miles so I'm hoping that's what it is. I will be so pissed off if it's an issue with the cylinder/head. I think I would trade it in at that point. Thanks again!

JK_Crawler

No need to trade, just do a Hemi or LS conversion. Cheaper then paying on another jeep or vehicle with a note for 5 or 6 yrs. from what I've read the 3.8L engines aren't 2XX,XXX mile engines, im already planning/saving for my LS conversion. I already have the engine and transmission so it should be a down ward slope from here.

07 Rescue Green

I hear ya on the engine swap, the issue is that I just bought this 3 weeks ago from a private party and I am making payments on it for 5 more years. I got a pretty good deal price wise but these repairs could eat that up quick (I'm having the heater core replaced next week). I noticed tonight that when I start it up when it's cold outside (low 30's) it tends to idle a little rough for about 20-30 seconds then smooths out. Everytime the check engine light comes on is when it's at idle right after start up. My question is could the CAI or the Viper TB be an issue? Thanks.

TWilson77

I am at 125k and had a similar issue. I changed out itens in this order

Plugs and wires (once removed noticed they were in really bad shape, especialy the plugs)
Cleared code but this time came back as p0300 and ran rough with intermitent smooth idle. Perplexed, I read alot of forums and troubleshooting that made me believe there was major issues. Thought about it and came to the conclusion that the code is no specific to a cylinder but a misfire is found.
Replaced coil with a refurbished as a test. About 5 min to install and have not had a p030x code since.

Since then I purchased a screamin demon coil and live wires. Def overkill but live wires are very very nice and with the ability to open plug gap to .65, I figured I already have a RIPP charger why not get the biggest hottest spark since I was already changing parts.

07 Rescue Green

Thanks TW, that's what I'm thinking, I'll do the wires, then the coil then??????????? I'll check out the live wires and screaming demon coil. My plugs were in really bad shape, thought for sure that would take care of it. I'm also going to fill up at a name brand station (I think its Texaco), where I live there is only one option for gas, a little no name mom and pop station, you have to drive 20 minutes to get Name brand gas.