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Unread 05-10-2013, 07:08 PM   #1
fordguy101
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Join Date: Feb 2013
Location: manchester, TN
Posts: 25
Misfire Error!!!

took my 2005 jeep liberty 3.7 V6 4x4 to the dealer to have it tested got the p2302 and p2311 number 1 cylinder and number 4 ignition coil....got new coils and just changed cylinder 1 and 4(started raining) it didn't fix it but did test for spark on the first cylinder and got spark...gonna change all spark plugs and coils tomorrow to see if that fixes it...


just wondered if anyone has had to deal with these codes and if anything else i may wanna look at while im under the hood (dealer wanted to put a new pcm in "go figure" but truck drives fine at times then at other times its racing rpms and jerking going into second gear let off the gas then ease back into it goes fine


i figured pcm wasn't the issue thanks for the help and info!

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Unread 05-10-2013, 10:11 PM   #2
streetglideok
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2005 KJ Liberty 
 
Join Date: Jul 2011
Location: Colorado Springs, Colorado
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Ok, seeing your name is fordguy, you know that ford numbers their cylinders differently than chrysler, or well anyone else for that matter. Are you sure you replaced the correct coils? It never hurts to rule out simple mistakes that could cause you untold headaches. If you do replace the plugs, make sure you install the correct NGK copper plugs, gapped at the spec on your emissions sticker. Never assume they are gapped right out of the box. Also, it should go without saying, dont waste your hard earned money on the junk at autozone. Get your coils from a reputable place.
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Unread 05-11-2013, 07:01 AM   #3
DaveJKJ
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^^yeah, I agree.

Some things you are better off using OEM parts....like plugs and coil-paks, and electrical stuff, when you are trying to fix a problem and clear codes.
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Unread 05-11-2013, 07:15 AM   #4
Dvdjhooper
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2002 KJ Liberty 
 
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I'm not saying this advice is going to solve your problem so please take it with a grain of salt. I have had some codes (indicating one thing or another) that couldn't be resolved until after a vacuum leak was fixed. Sometimes these vacuum leaks show further down the list than the codes that cause the dealer to go into a state of alarm. Misfire and throttle position sensor error codes are caused on my 2002 KJ by both small and large vacuum leaks and sometimes by a hung evap solenoid (gently disassemble and clean). The solenoid can get dirty from a vacuum leak.
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Unread 05-11-2013, 11:00 AM   #5
fordguy101
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yup was sure i changed the right ones front right side and second on the left (standing in front of the motor) fixing to change spark plugs and coils right now....got the ngk copper gonna gap at .040 and change em out...worried that it maybe a wiring problem have heard there been alot of people with animals getting to the wiring this year...but then again seems like a fuel issue since it bucks and carries on when giving it gas...probly a dang fuel injector on that cylinder gonna look if this doesn't fix it thanks again!


tps wsa changed recently due to the racing of the rpms...i have noticed since changing the 2 coils out lastnight its not shaking as bad as it was when u start it so maybe on the right path to change em all out with plugs
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Unread 05-11-2013, 01:52 PM   #6
fordguy101
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Update..... replaced coils and spark plugs still misfire...would crackshaft and camshaft sensors be a issue....its got good fuel pressure.... jeep has 122k miles on it
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Unread 05-11-2013, 04:50 PM   #7
streetglideok
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2005 KJ Liberty 
 
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If the crank or cam sensors were causing a problem, you would likely have it stalling out completely. You may want to disconnect the pcm connector(s) that have pins going to the ignition coils, and measure resistance from the coil to the connector. Also verify you have battery voltage at the ignition coil. It is possible you had a bad coil and it took out the driver in the pcm.
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Unread 05-11-2013, 09:49 PM   #8
fordguy101
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ok will do that next...if the driver got taken out would need a new pcm i take it?....was wondering if something is wrong with the pcm would the car still be driveable or would it not start etc?
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Unread 05-12-2013, 08:17 AM   #9
streetglideok
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PCMs, though rare, can fail in some form or another. I've seen a Nissan that lost its driver for the #2 injector, and I've seen a few chrysler products with IACs that internally shorted to ground, and cooked the drivers for them. In all those cases, the engine ran in some form. While its possible the pcm is bad, I always go out and prove it is bad before I condemn it. You should have a test light, you can use that to verify that the pcm is attempting to fire the coil. Verify which pin of the coil connector has battery voltage, and the other wire is the control from the pcm(ground). Run the test light from the + of the battery, start the engine, and touch the ground side of that connector. You dont have to murder the thing by forcing it into the connector. If you do that, youll need a connector too, good luck with that headache. If the light flashes, the pcm is pulsing the coil as it should. If it just stays on, or doesn't come on, you have a problem.
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Unread 05-13-2013, 06:27 AM   #10
AVR2
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1993 ZJ 
 
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Get your battery load-tested. It's easily overlooked, but a battery that's on the way out can cause misfires.

I was getting a CEL for random misfire, misfire in cylinder 1 and also insufficient ionization in cylinder 5. Since my KJ is 8 years old and on its original factory coils I figured it wouldn't hurt to replace them all. So all-new coils and plugs, and after a couple of days I had pending codes for random misfire and cylinder 1 misfire which turned into hard codes within a week.

I was starting to think about possible wiring problems (or worse) when I watched Scotty Kilmer's YouTube video about fixing misfire codes. His final suggestion was to get the battery load-tested, because a weak battery can trigger misfires even though it's still cranking the engine OK.

I went and got an electronic load test, and it came up "Replace battery". Not only that, but the mechanic pointed out that I had a undersized battery. At some point years ago, a quick-change battery place had fitted the wrong size of battery, and I'd just been having it replaced with the same size every time it died - which, being undersized, it did once every 12 months or so. I'd just put it down to bad luck and the KJ being hard on batteries...

Dropped in a proper-sized battery, and the misfire codes are gone.
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