info to start will help -
YOUR jeep is STOCK - no modifications (exclude tires, lift) ?
What plug - brand and plug #? ie ZFR6F - 11G ?
Do you have a SCANNER - able to see live data?
Does the engine reach correct temp?
Post ALL codes ....



2003 KJ 3.7L

 

My jeep is completely stock, the only thing done to it that I know of was done by the previous owner and it was a EGR delete. According to the temp on my gauge it does get it up to temp. But the exact plug numbers idk, I've put NGK Iridium IX and Champion Coppers in the car. Both with the same issue. And my scanner sadly cannot read live data but the code was just for misfire on #6 at the moment I believe it was P0306. Thank you for the reply

 

An EGR on a 2003 ? You got my attention now...something's not kosher.
Post ALL codes.
A thought - If your CEL is on take advantage of FREE scans at auto part stores.
I am wondering if you have a code reader not a scanner.

The plugs solid core thats good.

2003 KJ 3.7L

 

That's what I was told at purchase. I don't know if it was something just said to sell it to me. I've been told deleting the EGR was a good way to help prolong engine life so I didn't think much of it. I'm gonna mess with the scanner at the orielly I work at again and see if I can find a live scan function. Is there something to look out for on the live scan? But I did double check and the only code up that I can see at the moment is a P0306 I will look further into it

 

Sounds like something is fouling the plugs. What does the misfire one look like when you remove it?

 

They look kinda fouled out but not terrible usually. I currently can't pull cylinder 6 to check because I'm working right now. But they usually are a bit fouled but nothing to the point I think that would cause a misfire. But I did do an all module scan and found P0325 and P0330.

 

Those codes are knock sensor types.

Code:
P0330
Definition:
KNOCK SENSOR 2 CIRCUIT
Description:
Knock is the spontaneous auto-ignition of the remaining fuel/air mixture in the engine combustion chamber that occurs after normal combustion has started. It can occur under extreme vehicle operating conditions such as; excessive spark advance for the given engine operating conditionshigh engine temperaturehigh Manifold Absolute Pressure (MAP) Sensor valuelow humidity and heavy loads to the engineSevere, continuous knock may be caused by any of the following, but not limited to; carbon depositsbad gasoline and/or low octane fuel
Cause:

• KNOCK SENSOR 2 SIGNAL CIRCUIT SHORTED TO VOLTAGE
• KNOCK SENSOR 2 SIGNAL CIRCUIT OPEN
• KNOCK SENSOR 2 RETURN CIRCUIT OPEN
• KNOCK SENSOR 2 SIGNAL CIRCUIT SHORTED TO THE KNOCK SENSOR 2 RETURN CIRCUIT
• KNOCK SENSOR 2 SIGNAL CIRCUIT SHORTED TO GROUND
• KNOCK SENSOR
• POWERTRAIN CONTROL MODULE (PCM)

Code:
P0325
Definition:
Knock Sensor 1 Circuit
Description:
Knock is the spontaneous auto-ignition of the remaining fuel/air mixture in the engine combustion chamber that occurs after normal combustion has started. It can occur under extreme vehicle operating conditions such as high engine temperature, high MAP, low humidity and heavy loads to the engine. Knock is caused by excessive spark advance for the given engine operating conditions. Severe, continuous knock may be caused by carbon deposits, bad gasoline and/or low octane fuel. Avoiding light audible knock is important for customer satisfaction while preventing excessive knock is important to protect engine components. The output voltage from the knock circuit represents the strength of the engine knock and is read by the engine controller. The knock system output voltage is not zero due to engine background noise, even when knock is not present. When the engine is operated under high load conditions where knock is possible, the knock voltage is tested to decide if it exceeds the knock voltage threshold. Knock has occurred when the knock voltage is at or above this knock threshold. When knock is detected a calibrated short term knock spark retard to be subtracted from the spark advance is calculated. The amount of retarded spark advance is based off a calibrated severity of the knock event. This retarded spark advance is used in the next ignition event to prevent further knock events. If knock continues, an additional amount of short term spark advance retard is added. When knock stops, short term knock spark retard is eliminated, the long term knock spark retard is reduced by a calibrated amount to recover some previously retarded spark advance. This decreases spark retard to improve engine performance.
Cause:

• KNOCK SENSOR SIGNAL CIRCUIT SHORTED TO VOLTAGE
• KNOCK SENSOR SIGNAL CIRCUIT OPEN
• KNOCK SENSOR RETURN CIRCUIT OPEN
• KNOCK SENSOR SIGNAL CIRCUIT SHORTED TO THE KNOCK SENSOR RETURN CIRCUIT
• KNOCK SENSOR SIGNAL CIRCUIT SHORTED TO GROUND
• KNOCK SENSOR
• POWERTRAIN CONTROL MODULE (PCM)

There is also a TSB: https://static.nhtsa.gov/odi/tsbs/2020/MC-10176538-9999.pdf

 

the EGR on a 2003 still seams wrong.
removing the EGR is ILLEAGL.
Removing the EGR will not increase ENG life.
The missing component would set several codes. And you are not showing any.

Your using solid core plugs, new coils (did you use OEM) they are 1st suspects so we need more testing -.
This being a random and changing code is tough - I am thinking your going to need a scanner, check the freeze frame, and live data.
Other than a scanner I can only think of FUEL PRESSURE what is the PSI?

The 2 codes P0325 and P0330 - are they current ?

Do not erase codes..

 

Yeah, you need to look at live O2 sensor data. The engine could be running in a marginal condition thats eventually fouls a plug. When you replace one, the misfire just moves on to the next worse plug as it degrades. You could also be using poor fuel quality. If the P0325 or P0330 codes are current, there could be carbon buildup or low octane fuel.

 

Would you recommend trying to use a higher octane fuel? The P0325 and P0330 codes atleast just said stored, so I'm not positive if they're current or just old that never cleared themselves. But for the coils I didn't have them at my work so I went with the best coils we normally carry which were standard ignition coils. I did do a live scan last night and it said fuel sys 1 & 2 are CL I'm not sure what that means though. The 02 sensor B1 S1 said it was at 0.540 (v), sensor B1 S1 is 0.200 (v), B2 S1 was at 0.540 (v), B2 S1 is 0.160. Atleast according to the live scans I did.

 

as for the P0325 P0330 with the scanner Look in HISTORY, try to see if they are in freeze frame.

The CL indicates Cosed Loop . opposite of Open Loop - in closed loop engine is warm and sensors & computer are managing system. In open loop the system follows a program until warmed up and able to go into CL, the open loop will limit some performance anf MPG considerations.

The o2 sensors wil sweep ie .3v to .8v - seeing a fixed voltage is either a snapshot OR a malfunction that will generate a code.
YOU posted "B1 S1 said it was at 0.540 (v), sensor B1 S1 is 0.200 (v) " seams to indicate swing .200v to .540v
simply swinging .2v to .5v and that is LOW. the other sensor B2S1 is lOW also.

I would want to look at fuel pressure, or with the scanner look at Long Term Fuel Trim, it will have a - or + before a number that is important.
ALSO the Short Term Fuel trim same readings +or - post that...

 

The STFT B1 is sitting at anywhere from 1.6% to -0.8. LTFT B1 is staying at -1.6. STFT B2 is going from 1.6 to -0.8 and then dropped to -100 randomly. I have the car warmed all the way if that makes a difference and it's idling at about 600rpm

 

Experiance tells me fuel trims only go to + or- 33.

I have not seen -100 readings, I will try to figure that and low o2 voltages low out. I'll Post back later

Post the temp when warmed up.
Post ALL codes.

2003 KJ 3.7L