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Unread 09-28-2013, 12:22 PM   #1
karren
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Cylinder 4 Misfire/CEL on - can I still drive it?

My CEL came on and the dealer got the P0304 code but they can't look at until Monday (only do oil changes on Sat) - is it safe to drive? I need to go on a 160m roundtrip tomorrow...Help!

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Unread 09-28-2013, 12:58 PM   #2
Spank
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It's probably okay to drive in the short term. Disconnect the battery for a few minutes to reset the computer and see what happens. If it doesn't come back on immediately, you're fine for now, but should certainly get it looked at.
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Unread 09-28-2013, 01:03 PM   #3
karren
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Thanks for the response Spank
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Unread 09-28-2013, 01:13 PM   #4
222Doc
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I was told Yes, by our service manager. the day before our trip to Cali on a Thursday. went to the dealer, he said do the trip come back and bring it in. This trip was like 1k+round trip miles and some off road. Though at high altitude it was running rough at about 9k feet. it was then tossing multi mill codes for rich left bank and miss fire. made it home. took about week to get a head on it.

I would be it can very place to place. It took a week in all. Though I wish they would have done both sides. well this one ticked out at 20k. Trouble is from what I am reading on the net in other related forums is. this issue seems bigger than reported. I am seeing people code on 2013's from other forums and plat forms. If so then is this new head any better? by the time anyone knows the warranty will be over anyway. From what I can see in other plat forms they are coding later in life than in Jk's. Like most Jk's that show it early its from 5k-30k. But in other its more the 40+. To me this is not a good sign of what's to come.

Good thing to me, my Jeep is like a rifle. There are many like it but this one is mine, its my third and last. Once the warrants done and the pentaticker ticks its last breath. I'll go Chevy Ls nothing special might even go with a 6L80 for the mpg. though I like the W580 and as I PRIDICTED it was the best part of the new Jk's. At least it has not broke.(bazzinga).
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Unread 09-28-2013, 01:19 PM   #5
222Doc
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Quote:
Originally Posted by karren View Post
Thanks for the response Spank
DONT clear it. save it for the dealer.

Here is how it goes...for many, some may skip a step.

you code, they check it, reflash it if it has not been, send you on your happy a$$ way.

It codes again. They may do a Leak down test. It will fail as the exhaust valves are toast. they replace it, send you an you happy......
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Unread 09-28-2013, 07:50 PM   #6
Neo1130
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If the light is solid, then it's intermittent and not too big of an issue to drive. When it starts to flash while you're driving, stop the vehicle... This is a hard failure and when it's a hard fail, gas isn't getting burned and it all goes out the exhaust and can cause the cat to get excessively hot and melt down or can get in your muffler and literally blow it up like a balloon...

Solid - Keep driving
Flashing - Stop drivin' foo!
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Unread 09-28-2013, 08:35 PM   #7
tjkj2002
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Quote:
Originally Posted by Neo1130 View Post
If the light is solid, then it's intermittent and not too big of an issue to drive. When it starts to flash while you're driving, stop the vehicle... This is a hard failure and when it's a hard fail, gas isn't getting burned and it all goes out the exhaust and can cause the cat to get excessively hot and melt down or can get in your muffler and literally blow it up like a balloon...

Solid - Keep driving
Flashing - Stop drivin' foo!
X2...........

Flashing = 's cat damage or internal engine damage is occurring,not "it may damage" but is damaging.
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Unread 09-28-2013, 08:48 PM   #8
mello
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Flashing means there is a cylinder misfire above threshold. A solid light can be a hard fault code just as much as not. Most things will not even turn the light on until they fail so many ignition cycles. A OBD II engine can have a misfire that can be easily be felt by driver but not bad enough to turn light on. A lean condition is one of the main things that will burn up a cat and it will have a solid light not a flashing one.
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Unread 09-29-2013, 08:20 AM   #9
jwmbishop
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So the JK is opposite all other on board systems?

Where intermittent flashing occurs while writing a soft (pending) code - some softies can hit three or four times before they hard code (one misfire will not light the light - it takes a few pending codes to equal a hard code) and keep it illuminated. Of course I have never seen a constant flash.
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Unread 09-29-2013, 08:30 AM   #10
Neo1130
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Quote:
Originally Posted by jwmbishop View Post
Of course I have never seen a constant flash.
You've never driven a VW or Audi with bad coil packs then huh?!
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Unread 09-29-2013, 09:03 AM   #11
jwmbishop
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Quote:
Originally Posted by Neo1130 View Post
You've never driven a VW or Audi with bad coil packs then huh?!
True - I've never driven anything with bad packs - I tend to tow (thank God for AAA) and fix em - not drive em - when things go bad.

But ford 4.3 (08 towncar) and GMLS1 (04 GTO) with bad packs flashed the light at least three different times before going solid went solid (at solid the mis was noticeable.. 4.3 in Merc flashed four times, never went solid and had a mis fire pending (heater core leak had caused overheat - reset and no code repeated).

Good to know constant flash does not mean unable to write the code successfully - usually from a bad pRom (which I recall was the message from my days in school - when OBD1 was then current platform).
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Unread 09-29-2013, 09:07 AM   #12
222Doc
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Jeep wishes it was just a bad spark pack. Those are cheep to replace compared to heads.

No the Jeep will just hard code. If it gets to a point Limp mode could come to play? never has from what I have read anywhere. BUT again the OP Question is can he go 300 miles. Well no one can say 100%, murphy is a bit**. But I know mine had no trouble going well over1K miles on our wheeling trip this year. with the leaky valves. the wheeling trip was more important to me, as long as the dealer said go.

The Op may well not code again right away depends how bad the leak is at the Valve. I did notice though. My first trip to the dealer. all they did was record the code/check then reflashed the Jeep. I think they change the parameters of these codes. my next code 2 days later was P300, multi miss fire. I never seen the first ones again p302.
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Unread 09-29-2013, 11:16 AM   #13
tjkj2002
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Quote:
Originally Posted by jwmbishop View Post
So the JK is opposite all other on board systems?

Where intermittent flashing occurs while writing a soft (pending) code - some softies can hit three or four times before they hard code (one misfire will not light the light - it takes a few pending codes to equal a hard code) and keep it illuminated. Of course I have never seen a constant flash.
No such things as "soft codes",there is pending codes.Flashing means damage to cats is happening.


All engines misfire all the time just not enough to make it run rough or cause any issues.
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Unread 09-29-2013, 01:44 PM   #14
73azbronco
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Drive it like you stole it, don't reset it, welcome to the club.
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Unread 10-07-2013, 07:52 PM   #15
karren
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A quick update...dealership fixed it by replacing whatever it was that needed replacing. Was able to drive it prior to repair with no problems. I am just thankful that the CEL came on while under warranty....
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