P0300 code along with 3 seperate cylinders Renegade Liberty 2003 3.7

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GitEmSteveDave

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So Sunday after work I went out to leave and in between starting it up and running back inside to get my sunglasses, I had a CEL, first in months since the dealer fixed everything, and back then it was an 02 sensor.

I pulled the code with TorquePro and got this P0300, P0302, P0303 & P0305 IMG LINK. As soon as I could I googled, and of course, the advice from both here and elsewhere was all over the map. From a $8 ASD relay, to $2,000+ in multiple repairs, to "just clear the code and it will be A.O.K. b/c it was a bad fillup"

So when I got home I used my Harbor Freight scanner to clear the code. I had just put $20 in, so I figure it might have been a bad tank of gas, b/c how else can 3 spark plugs go bad all at once, and this was on startup after sitting for ~6 hours?

So far it's been three days of no codes, and the scan tool/Torque Pro's Emissions Tab finally reads green, b/c it was yellow for three full cycles, I guess b/c of the cleared code. Is there anything I can do to make her keep running OK? She doesn't feel like she's mis-firing, aside from a an occasional "shiver" when sitting at a stop light occasionally.
 

LibertyTC

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What brand model # of spark plugs are installed? Underhood sticker recommends NGK-ZFR 6F-11G (copper core)
Pull one or more of the plugs and inspect burn condition of plugs...are they clean no fouled?
Have you ever changed the coil packs or are they still the OEM's?
If bad gas is suspected, get a fuel conditioner, or some marine ethanol staybilizer like Star Tron-Starbrite.
Have you ever cleaned the throttle body with IAc cleaning & ports etc?
 

JasonJ

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Cylinders 2, 3 and 5... yeah that is random and multiple alright. If you had just fueled up.. it could be that. Would be interesting to know then why it wasn't all cylinders, although the way things work it could have only misfired on those cylinders, depending on about 3-dozen other variables.

If it's been fine since, I'd second the fuel treatment advice- even though there are cleaners and additives in refined gasoline, clearly something is off. Some Tech-ron or Berrymans B12 might be in order. Then keep an eye on it.

If I had to start blaming parts, coils would be a good one to start at. Of course, start by swapping suspected bad coils with ones that have no exhibited issues.. spark plugs- are they the proper NGK's and how old? I did get away with using Autolite copper plain-jane plugs for a number of years and miles, but the NGK's are much better running. Even on my original coils (fingers-crossed/knock on wood).

Let us know how it goes... does your Torque app show you injector duty cycle, fuel trims or anything like that? Might be something to keep an eye on to see if it fluctuates outside of normal.
 

GitEmSteveDave

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I've only had the Jeep for ~6 months, so I am not sure what's installed under the hood or it's service history prior to getting it.

Not sure everything that the app can show me, but I only use it to display voltage, coolant temp, intake temp, speed, RPM, and throttle percentage. I'm not sure how much info the 2003 computer gives up to an app though.
 

LibertyTC

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Ya start with the plugs. They run hot & can eat the gaps every 30k miles.
You can tell a lot by the burn/color/condition of the plugs themselves.
Post back some pics of the removed ones, & be ready with a new set to install.
The Jeep runs great with these.... check/set gap too.
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GitEmSteveDave

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Not sure about pulling the plugs. I had no problem on the Cutlass Supreme and the Sunbird, but the coils on top intimidate me. Any good YouTube videos to teach me? Are these the right plugs? https://www.amazon.com/NGK-ZFR6F-11G-V-Power-Spark-Plug/dp/B000GZGV3E

I topped her off this morning, parked,and after I got my coffee, I started her up and she gave me an Airbag light. I ran the scan for codes and p0300 came up as pending(was NOT present before fillup and when I started it 20 minutes earlier). I drove her to work and when I cycled the ignition, the air bag light disappeared but P0300 was still pending. After work(still showing pending p0300) I bought two bottles of Techron and one of SeaFoam when I stopped to buy dinner supplies. After dinner I put a bottle of Techron in, started up and scanned for codes after she hit operating temp(159F) and no p0300 code.
 
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JasonJ

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Not sure about pulling the plugs. I had no problem on the Cutlass Supreme and the Sunbird, but the coils on top intimidate me. Any good YouTube videos to teach me? Are these the right plugs? https://www.amazon.com/NGK-ZFR6F-11G-V-Power-Spark-Plug/dp/B000GZGV3E

Yes those are the correct spark plugs. Check your local stores as well though, I was able to get mine about a a dollar cheaper per plug locally.

As for the coils, don't let it bother you. It's stupid simple. A 10mm nut that holds them down, some have plastic clips on the studs sticking up that you pop off and set aside- those hold evac tubes and things like that. One or two have another 10mm nut under the plastic tube clips.

Then undo the electrical connector and pull straight up. Just make sure you have a one-piece socket extension.. or wrap tape around the connections if you're sticking a few 3" extensions together. It ***** when the separate and leave your socket at the bottom of the hole.

I also like magnetic spark plug sockets, instead of the rubber filled ones. It's not hard at all. Just be mindful of how the coils unplug, so you don't break the connectors.
 

GitEmSteveDave

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If there a guide on here about changing them? I live alone and don't have a 2nd vehicle, so I'd like to know I have everything before I start a job, so I don't end up needing a bottle of samoflange powder, when I have all the plugs out. Would replacing the coils be a good idea as well? Where's the best place to get those? Who makes the best ones? RockAuto goes from $15 to $35 each.

EDIT: I've tried checking the HowTo section, but it's not easy to find the best "guide", and I'm already 13 pages into the section. I'd like to know tips, like what sparkplug socket size to get, and also if I need dielectic grease and anti-sieze. I'm worried I'll find a great guide, but the picts and links will be out of date.
 
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LibertyTC

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10mm nut resides on the top of each coil pack remove it, & the electrical connector by pressing tab down and pull back see video at 4 min 30 sec aprox.
https://www.youtube.com/watch?v=DxsEOCqhHx8
Then pull up on coil pack to remove it. Use compressed air to ensure no debit or dirt is in the spark plug bore.
This photo may help..
62188[/ATTACH]"]
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Remove plugs when engine cool only!
I use electrical tape from the 5/8 spark plug socket to extension.
This ensures that when you pull up on the plug after loosening it, it will come up & not just leave the socket in the bore !!
I apply a very light sniff of anti-seize to the new spark plug threads, use a lint free towel to remove most of it leaving only a tiny bit in threads.
The die electric grease is used for the along the bottom of the coil pack boot.
I also use some on the coil rubber seal to keep it fresh.
Access to plugs is pretty good, I do move off to the side the coolant reservoir, by removing the nut only.
Some may feel the need to use a swivel on the passenger side rear plug, I've managed to do without one.
If you do use a swivel once again electrical tape to hold things together.
I can do all 6 plugs taking my time in 45 minutes.
Hope this helps.
 

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LibertyTC

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Oh & as far as replacement coil packs- OEM from Mopar is the best..but pricey.
I used Standard so far with good success, now 2 years later.
Many should consider new coil packs as part of a good tune up after 60-75k miles.
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GitEmSteveDave

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Oh & as far as replacement coil packs- OEM from Mopar is the best..but pricey.
I used Standard so far with good success, now 2 years later.
Many should consider new coil packs as part of a good tune up after 60-75k miles.

I'm looking on RockAuto right now and there are Standard UF270($15) and UF270T($10). T's are cheaper and they are described as "a fit whenever a commercially acceptable product is called for." I also notice NGK makes an ignition coil for $18 "NGK 48651 {#U5053}". Since they make the plug, I would think that their coils would probably be best matched, right?
 

GitEmSteveDave

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10mm nut resides on the top of each coil pack remove it, & the electrical connector by pressing tab down and pull back see video at 4 min 30 sec aprox.
https://www.youtube.com/watch?v=DxsEOCqhHx8
Then pull up on coil pack to remove it. Use compressed air to ensure no debit or dirt is in the spark plug bore.
This photo may help..
62195[/ATTACH]"]
You must be registered for see images attach

Remove plugs when engine cool only!
I use electrical tape from the 5/8 spark plug socket to extension.
This ensures that when you pull up on the plug after loosening it, it will come up & not just leave the socket in the bore !!
I apply a very light sniff of anti-seize to the new spark plug threads, use a lint free towel to remove most of it leaving only a tiny bit in threads.
The die electric grease is used for the along the bottom of the coil pack boot.
I also use some on the coil rubber seal to keep it fresh.
Access to plugs is pretty good, I do move off to the side the coolant reservoir, by removing the nut only.
Some may feel the need to use a swivel on the passenger side rear plug, I've managed to do without one.
If you do use a swivel once again electrical tape to hold things together.
I can do all 6 plugs taking my time in 45 minutes.
Hope this helps.

Thanks for the picture! Now I Know I need a 5/8" spark plug socket. I tried that video earlier, but turned it off when the guy was telling me there were spark plugs behind the steering wheel. I'll check my supply of extenders tomorrow.
 

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JasonJ

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Thanks for the picture! Now I Know I need a 5/8" spark plug socket. I tried that video earlier, but turned it off when the guy was telling me there were spark plugs behind the steering wheel. I'll check my supply of extenders tomorrow.

Your location is listed as Howell... in which state. There is a Howell in Michigan, where I live. If it's the same, I could help you in person.

Have you peeked under the hood yet to see what you're getting into? If you haven't do, and you'll see it's not bad at all. Honestly, i find it easier than changing the headlight bulbs in the KJ.

As far as tools, yes, 5/8" spark plug socket (again, I spent a bit more and got a magnetic one, which I've been using for 10+ years, it's worth it in my mind).

Also will need the 3/8" ratchet, of course. And at least 3, 3" extensions, or a single 8" will do as well.

A 10mm socket, deep well. I use my 3/8" drive ratchet and a deep socket here, because the socket needs to go over a few longer studs on some of the coils.

A tiny flat screwdriver may be needed for some of the coil connectors, if they stick a bit.. usually just push the tab and gently pull.

That should be it for tools. Not sure if it is just me, but for the passenger side I remove the coolant overflow tank as well, and use mechanics wire (or string) to hold it out of the way in order to get at the back cylinder. I also remove my intake tube to the throttle body- for more space to work.
 

GitEmSteveDave

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OK, replaced coils and sparkplugs. Starting up the first time I got a pending misfire on Cylinder 1, which cleared on it's own w/o lighting up the Check Engine Light. But over the past week, I have gotten two separate pending Cylinder 3's, which haven't triggered a CEL, but my tablet w/bluetooth OBDII adapter scans for pending codes every few minutes, and they pop up right after starting and eventually clear on their own. I don't really feel anything, except an occasional "shiver" when at stop lights sometimes.

Gonna add a bottle of seafoam the next time I fill up and maybe drive w/o OD to push it through. If not, any suggestions as to what it could be? I had someone help me gap the plugs, so I know they should be alright, but I'm not above pulling the coil and plug again and checking everything. Or should I just ignore it until it generates a CEL?
 

LibertyTC

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I've seen on a snap on scanner random misfires on my KJ and never set a engine light or code set. It can take up to 1000+ misfires before it may set a code....
Ya you can ignore it until it does set a code/s
This 3.7 engine offers a slight shake at idle, after all said.. it's an odd fire V-6.
If you ask me, contributing factors are injectors & put put city driving & carbon build up issues.
The other is quality of lower octane gasoline's & especially winter blends in general.
I run higher octane non ethanol Chevron 94 with a 2 bottle mix of chevron techron concentrate, and a solid long distance hwy boogie to blow the dust out.
Another consideration would also be new injectors or get em cleaned professionally or a dealer service, (emission service) where they use pro chemicals direct injected into fuel rail, and watch the carbon go bye bye!
Last weekend I had with the drivers door open at idle, noticeable shake happening again..
I added a half a bottle of Star-Tron and there was an immediate improvement !
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GitEmSteveDave

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Yeah, I put a bottle of Techron with my last half fill up, which I figured would be like adding 2 bottles to a full tank :) We will see what a complete fill up and treatment does to her tonight.

I love this Jeep, but every little thing worries me about her. I sometimes find myself cruising with the windows down enjoying myself, and then someone ahead of me will be burning coolant or pass me with squeaky belt or knock and I think it's me. Even though she's only ever had radiator leak, water pump seal leak, and a bad upper control arm, and I see how long a KJ can last if you just give it a little TLC, I just....worry.
 

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These KJ shake a small amount at idle. Mine was bad, replaced the OEM plugs (Horrifically worn down) and it was instantly at least 60%+ improved idle.

I run my KJ VERY hard and often floor it many times as the power is very mediocre. I do have a lift and larger tires which is less than ideal with the 3.73 gearing.

Ever since ive been flogging it its ran very well, no noticeable shaking or anything. Italian tune up is highly recommended. I also run EBC yellowstuff and EBC dimpled and slotted rotors for heavy breaking, as I brake very aggressively. HIGHLY recommend those brakes!
 

GitEmSteveDave

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Well, the pending P0300, P0301 & P0303 from this morning:
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Turned into a solid code after starting her up at work tonight:
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So what should I do? Should I pull the plugs and coils and re-check them?
 

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