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Unread 08-18-2010, 11:19 AM   #1
straty1987
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WJ giving a code, need advice

its a 2002 GC limited 4.7

was driving someone this morning and noticed the malfunction indicator lamp (mil) light was on. so after i drooped them off i went to auto zone to get it scanned and came up with the P0300 code.

came home and looked up how to to the trick with the key and came up with P0300 and P0308.

some more info:
i changed all 8 spark plug with anti-size and dielectric grease.
i only put a little dielectric grease on the coil o-ring and smooth it around with your my finger. same thing with the anti-size on the threads. also checked all the gaps before putting them in the plugs and they were good.
that was done on 7/22/10 at 44211 miles and now around 44680 miles (over 450 miles). took a trip that was mostly highway and driving has been good. its driving good now too just i need to clean the TB and sensors at some point

i know P0308 manes the 8th spark plug, just is that the last one on the driver or passenger?
i believe the coils are numbered.
the one on the passenger side is a pain to get but i changed it after some workaround. i think it might be loss and need a tightening.

engine is warm but all the plugs are on the coils good and coils are in good. guess i will have to wait till it cools
down to get to the 8th cylinder looked at.
but anyone have any advice on what to do for the P0300 code?
should i recheck all the plugs and coils and clear the code or see if it clears it itself?

thanks for your time and any info on it


Last edited by straty1987; 08-18-2010 at 12:14 PM..
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Unread 08-18-2010, 11:57 AM   #2
99JGCWJ
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The misfire detection monitor, a software strategy built into the computer, is designed to detect an engine misfire. The computer can also normally identify the specific cylinder in which the misfire has occurred. A misfire is nothing more than a lack of combustion, which can be caused by poor fuel quality or metering, low compression, lack of spark or unmetered air entering the engine. There are other possible, less obvious causes as well, such as uncommanded Exhaust Gas Recirculatin (EGR), flow. When the misfire monitor detects a misfire, it will trigger the check engine light with the specific cylinder number as the last digit in the P030X code. For instance cylinder 1 misfire is P0301, cylinder 2 is P0302 etc. In this case we are left with a P0308 in the computer memory.

Possible Causes:

Fuel injectors, related wiring, sensors and computer issues
Running out of gas, or poor fuel quality
Evaporative emissions system (EVAP) concerns: fuel vapors leaking into engine
Incorrect Fuel Pressure
EGR system concerns: leaking EGR valve or restricted ports
Base engine concerns: low compression, valve train problems and timing issues
Ignition system concerns including, but not limited to:
Faulty spark plugs
Faulty coil or related wiring
Ignition module or related wiring issues
Ignition related sensor faults or wiring issues

Hope this helps.
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Unread 08-18-2010, 12:04 PM   #3
straty1987
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Quote:
Originally Posted by 99JGCWJ View Post
The misfire detection monitor, a software strategy built into the computer, is designed to detect an engine misfire. The computer can also normally identify the specific cylinder in which the misfire has occurred. A misfire is nothing more than a lack of combustion, which can be caused by poor fuel quality or metering, low compression, lack of spark or unmetered air entering the engine. There are other possible, less obvious causes as well, such as uncommanded Exhaust Gas Recirculatin (EGR), flow. When the misfire monitor detects a misfire, it will trigger the check engine light with the specific cylinder number as the last digit in the P030X code. For instance cylinder 1 misfire is P0301, cylinder 2 is P0302 etc. In this case we are left with a P0308 in the computer memory.

Possible Causes:

Fuel injectors, related wiring, sensors and computer issues
Running out of gas, or poor fuel quality
Evaporative emissions system (EVAP) concerns: fuel vapors leaking into engine
Incorrect Fuel Pressure
EGR system concerns: leaking EGR valve or restricted ports
Base engine concerns: low compression, valve train problems and timing issues
Ignition system concerns including, but not limited to:
Faulty spark plugs
Faulty coil or related wiring
Ignition module or related wiring issues
Ignition related sensor faults or wiring issues

Hope this helps.

thanks for the post, read that on engine-light-help.com but nothing that is new to me, every thing in books or online says the same thing
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Unread 08-20-2010, 08:23 PM   #4
straty1987
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finally had time to get to the jeep. as soon as it cooled down on Wednesday started to rain and Thursday i had to help a freind.

i cheeked the 8th plug and it was gaped right and nothing looked odd. but i put a new on in since i bought 2 extra in case one broke when i instated them. so i check all the other plug and their gaped good too. the anti size i put on made it allot easier to take out the plugs compared to when i changed them a while ago.

code is gone since i disconnected the battery but will see if it comes back in a few days after driving around. but is idling good

I also cleaned the IAC and the end was dirt, now i can see the metal on the end. cleaned the throttle body mounted as best as i could but got allot of dirt off with a towel.

can the TPS be cleaned?
i know it can effect the idle or cause a odd shift from reading around.

the 5.25oz bottles of Lucas Fuel Treatment is on sale for $5 at auto zone so will put one in during my next fill up might buy an extra for another time and see if it helps.
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Unread 08-20-2010, 10:01 PM   #5
freakinheep89
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the TPS should not need to be cleaned, as it does not intake any air, just sends a signal based on how much the throttle body is open. if its faulty, replace it.
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[QUOTE=slayercr23;12630497]How would i go about Stroking it?[/QUOTE]
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Unread 08-20-2010, 10:28 PM   #6
straty1987
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Originally Posted by freakinheep89 View Post
the TPS should not need to be cleaned, as it does not intake any air, just sends a signal based on how much the throttle body is open. if its faulty, replace it.
ok that's what i thought.
a few times the jeep has a odd jerk were it fells like its shifting and though t could be form the TPS guess will look into dealer and aftermarket
Thanks
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Unread 08-20-2010, 10:54 PM   #7
freakinheep89
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if its a sudden jerk it sounds more like a coil. that would also explain the misfire
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[QUOTE=slayercr23;12630497]How would i go about Stroking it?[/QUOTE]
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Unread 08-20-2010, 11:30 PM   #8
straty1987
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Quote:
Originally Posted by freakinheep89 View Post
if its a sudden jerk it sounds more like a coil. that would also explain the misfire
when the jeep had the light i had the jerk of a misfire 2 times on Wednesday and the idle was crazy. nothing like the one i mentioned above.
all the coils look fine and good but if it comes back will look into a replacements.
i see at auto zone there $33 each so might talk to a part out guy.

the coil looks to be just a tube of plastic with a spring that touched the top of the plug and the connection at the top which is just 2 wires.

i cleaned the extra connection that attach to the coil mounts bolts since they had some dirt.

will see what happens tomorrow when i drive around,
if i have a misfire can anything be damaged?
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Unread 08-21-2010, 08:36 PM   #9
freakinheep89
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yes eventually. each misfire is a failure to combust in a cylinder. the motor runs on the principle that there will be an explosion to propel the cylinder down. when it misfires, the other cylinders working and the torque from the crank have to pull that cylinder down and actually can damge the rings if it is done for a while. one of the coil wires popped off a 2010 camaro at work and it actuall spun a rod bearing due to the constant misfire
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[SIZE="1"][B]95 ZJ 5.2[/B]- D30/XJ shafts/D35 Yukon alloys,249, 2"BB, 30x9.5"Wildcat EXT,lots of motor mods, rancho shocks & stabilizer.[/SIZE]

[QUOTE=slayercr23;12630497]How would i go about Stroking it?[/QUOTE]
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Unread 08-21-2010, 09:42 PM   #10
myjeeplovesmud
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Quote:
Originally Posted by freakinheep89 View Post
the TPS should not need to be cleaned, as it does not intake any air, just sends a signal based on how much the throttle body is open. if its faulty, replace it.
couldn't agree more... yeah it sucks to stick 100 bucks on something so tiny but at the same time, its really worth it. i'd tell anyone with a jeep over 100k to to replace it. you will see the mpg jump, a better idle and performance hike.
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Unread 08-21-2010, 09:58 PM   #11
freakinheep89
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Quote:
Originally Posted by myjeeplovesmud View Post
couldn't agree more... yeah it sucks to stick 100 bucks on something so tiny but at the same time, its really worth it. i'd tell anyone with a jeep over 100k to to replace it. you will see the mpg jump, a better idle and performance hike.
100 what? that better be pesos. i paid $36 from the mopar dealer for my TPS
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[SIZE="1"][B]95 ZJ 5.2[/B]- D30/XJ shafts/D35 Yukon alloys,249, 2"BB, 30x9.5"Wildcat EXT,lots of motor mods, rancho shocks & stabilizer.[/SIZE]

[QUOTE=slayercr23;12630497]How would i go about Stroking it?[/QUOTE]
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Unread 08-22-2010, 02:28 AM   #12
straty1987
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Quote:
Originally Posted by freakinheep89 View Post
yes eventually. each misfire is a failure to combust in a cylinder. the motor runs on the principle that there will be an explosion to propel the cylinder down. when it misfires, the other cylinders working and the torque from the crank have to pull that cylinder down and actually can damge the rings if it is done for a while. one of the coil wires popped off a 2010 camaro at work and it actuall spun a rod bearing due to the constant misfire
thanks for the info good to know a bit more on it.
i only drove the jeep for a bit under 5miles so i dont think i did much damged


Quote:
Originally Posted by myjeeplovesmud View Post
couldn't agree more... yeah it sucks to stick 100 bucks on something so tiny but at the same time, its really worth it. i'd tell anyone with a jeep over 100k to to replace it. you will see the mpg jump, a better idle and performance hike.
my jeep is just a bit under 45K so i have soem time to go but i know parts wear after some time

for my 02 4.7 TPS at auto zone is $32 with 2 year warranty so idk how much it would be at the dealer. but i have notiec jeep/Chrysler cars dont like aftermarket parts sometimes
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Unread 08-22-2010, 02:35 AM   #13
straty1987
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well did a 100 miles on the jeep mixed highway 60% and city 40% and was all good. no funny shift or odd idles, but i had tools and parts with me if need.
i took the same tools and parts with me on my on my 450 mile trip and a few days after i took them out i got the codes, so i dont know if the jeep is messing with me lol.

i dont know if its the plug in the 8th spot that had something wrong with it since looks just the the other when i pulled them, but switched it anyway to make sure. but this seams odd to me so will see what happens.

is getting used coils a good idea?
i can get 8 used (part out) for the same price of a new one at auto zone
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Unread 08-22-2010, 07:46 AM   #14
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Wj

It wouldn't hurt to have them, but you would need to install a couple of them and run them for a while to see if they are good, otherwise your troubleshooting will be compromised.

I don't know if it got mentioned earlier but, swap the #8 coil and/or plug with one of the others and see if the problem follows the swapped part or not. Make sure your connectors are not damaged as well.
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Unread 08-22-2010, 02:53 PM   #15
straty1987
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Originally Posted by jtcnj View Post
It wouldn't hurt to have them, but you would need to install a couple of them and run them for a while to see if they are good, otherwise your troubleshooting will be compromised.

I don't know if it got mentioned earlier but, swap the #8 coil and/or plug with one of the others and see if the problem follows the swapped part or not. Make sure your connectors are not damaged as well.
the reason why i did not switch the coil is to see if it the plug, if it comes back will swap the coil. all the cables are good when i looked.
the coil looked fine but something could be messed up inside i guess.
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