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-   -   still getting a misfire.. why? (http://www.jeepgarage.org/f181/still-getting-a-misfire-why-54719.html)

paroxysym 02-13-2013 01:16 PM

still getting a misfire.. why?
 
So a couple weeks ago I got a CEL for a misfire on cylinder 2. Cleared it with my SC and did alittle research. Ran a bottle of techron and a full tank of gas through the jeep, followed it up with a second bottle of chevron injector cleaner with techron and still the CEL came back. So this past weekend I swapped the cylinder 1 coil pack with cylinder 2 and replaced the spark plug in cylinder 2. I also threw a bottle of seafoam in the tank and took a drive out of state. Tonight it's back and I don't know where to go from here.

Thoughts fellas? I keep clearing it with my SC, is that bad?

brentwoodkris 02-13-2013 02:47 PM

Re: still getting a misfire.. why?
 
Is the misfire for the same cylinder as before? Or did it follow the coil pack? If it followed the coil pack, it's probably a bad pack. I noticed that you didn't say you pulled the plug, and it could just be a fouled/bad/wrong gapped plug. I know with my 5.7L, they're picky about plugs...If you have a lot of miles, might be a time for a full tune up. Also noted that you didn't mention the age of the wires and if they're OEM, etc. Be sure to checkk those too. Have you done any work to it recently that would have affected the ignition system?

paroxysym 02-13-2013 04:39 PM

Re: still getting a misfire.. why?
 
well the plugs maybe have 15k on them and i pulled the plug from cylinder 2 and replaced it with a new one and properly gapped it. the code stayed with cylinder 2 after changing coil packs. also what wires are you talking anout? i was thinking of running a can of seafoam through the brake booster as well, but wouldnt that require me to change all my plugs afterwards?

this is frustrating, i hate CELs

brentwoodkris 02-13-2013 04:51 PM

Re: still getting a misfire.. why?
 
Oh whoops I see you have a 08 4.7. My 05 5.7 has a wire loom or shorties if people replace them. You probably just have 8 plugs, and I have 16...a few differences. Regarding the seafoam, I ran 1/2 a can through my booster and didn't swap plugs afterwards with no performance loss.

CELs can be tricky. Hopefully someone with more knowledge about your specific motor will chime in soon.

DannyVtCa 02-13-2013 04:55 PM

Re: still getting a misfire.. why?
 
Check compression in that cylinder to see if your valves and rings are alright. You have any coolant loss? Those 4.7 are notorious for sludging the oil drain backs and causing head gasket failures. My brothers blew the head gasket on a '02 high output and my father in law blew one on his '01 durango. Coolant will misfire a cylinder. But, I'd lean more towards ignition and compression first, wires, injectors, coil pack. If the swapping of coil pack didn't solve it. Get a new injector, hemi injectors are 40-50 bucks... Yours must be less. It's not hard at all to take the rails off and pop a new injector in. If your compression is wrong, well... New valves will be needed and that I don't know about.

DannyVtCa 02-13-2013 05:04 PM

Re: still getting a misfire.. why?
 
Leak down tests are a bit more complicated and tell you more. To do a compression pop the fuel pump fuse out. Remove all the spark plugs from one side, thread compression gauge in and crank her over. Hopefully it's not the problem and just a bad fuel injector, but its good to know if you have any cylinders starting to lose compression. I find it pretty relaxing working on my jeep, I think of it as a little bit of garage therapy. :-)

paroxysym 02-13-2013 10:20 PM

Re: still getting a misfire.. why?
 
It went out today. I'm thinking the seafoam probably ran its course. I filled her up with a fresh tank of premium so lets see how this pans out.

paroxysym 02-18-2013 11:29 AM

Re: still getting a misfire.. why?
 
meh its back again... damnit!

robpp 02-18-2013 01:05 PM

Re: still getting a misfire.. why?
 
egr?

paroxysym 02-18-2013 01:57 PM

Re: still getting a misfire.. why?
 
Quote:

Originally Posted by robpp (Post 762281)
egr?

ehhh i had the dealer change that around 75k? they could have not, i wish i stayed with the jeep when they did it.

ill have to take a look.

is there any foreseeable damage if i just continue to clear the code and continue on with it? its not running rough or anything- it does get alittle jumpy/rough when i lug her in OD, but i usually give her some gas and kick her down a gear.

ALPINEST4RS 02-18-2013 02:03 PM

Re: still getting a misfire.. why?
 
if you replaced the plug and swapped coils and it still on two.. sounds like carbon build up on the valve gap. leakdown test is the way to go..

if you continue to run the car misfiring, you can melt the converter down costing you big down the road.

paroxysym 02-18-2013 02:56 PM

Re: still getting a misfire.. why?
 
Quote:

Originally Posted by ALPINEST4RS (Post 762306)
if you replaced the plug and swapped coils and it still on two.. sounds like carbon build up on the valve gap. leakdown test is the way to go..

if you continue to run the car misfiring, you can melt the converter down costing you big down the road.

Is it worth running a can of seafoam through the brake booster? would i need to replace all the plugs afterwards?

leak down test?


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