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Engine missing

20K views 33 replies 11 participants last post by  imrustee 
#1 ·
We just acquired a 2007 wrangler, I have replaced the coil pack, plugs and wires and still have a pretty good miss. Getting random misfire codes. What would be the next thing to check or replace in this frustrating process of elimination. Any help is much appreciated. 3.8 L
 
#4 ·
Don't misunderstand, I'm not saying that is what it is, This is just a stab in the dark just as any parts swap diagnosis is.
I assume you do not have a full fledged diagnostic tool that you would be able to monitor the sign wave/pulse of the CPS to confirm there is a skip in its function, so until we are all equipped with this sort of diagnostic equipment it's either parts swap diagnosis or bring it to a shop and pay for their equipment.
For the most part it's what I am left with also when things don't function as they should, Good Luck.
 
#6 ·
I bet if you look under the hood you'll find the engine. :p

Seriously though, it could be any of a number of things.

I had a bad batch of gas cause multiple random misfires. It had some water in it. And water doesn't burn as well as gas.

It could be spark plugs or wires. It could be a bad connection at the coil. It could be a bad coil.
 
#9 ·
Happy to be of service. :)

My trouble with the bad gas showed up the day after I filled up. The water settled overnight and caused the "multiple random misfires" code to show up the next day as soon as I got on the freeway a few blocks from the house.

Just one more thing to look into.
 
#10 ·
We just acquired a 2007 wrangler, I have replaced the coil pack, plugs and wires and still have a pretty good miss. Getting random misfire codes. What would be the next thing to check or replace in this frustrating process of elimination. Any help is much appreciated. 3.8 L
Can you provide the codes?
Without the them, any 'help' would really just be a guessing game with you footing the bill (in parts).
 
#13 ·
Sounds like a fuel delivery issue. Could be clogged injectors or crap in your fuel line. I'd start with a fresh fuel filter and run a tank of fuel system cleaner through the Jeep. That might fix it and doesn't cost much at all.

If not, you may need to replace injectors or the fuel pump.
 
#17 ·
Lean and Misfire would point me to fuel as well. If it were misfiring on the ignition end, it damn sure would not be lean on that bank as it would be dumping raw/unburnt fuel from that cylinder that didn't burn at ignition.

That's my $.02. Other things could be a compression issue ($$$) or a bad CPS as mentioned as well, but I think it would be a constant issue if either of those were going on.
 
#18 ·
Overly lean conditions can also lead to misfires if you get them lean enough.

A clogged injector could be all that's wrong and a bit of cleaner may be all it takes.

It's likely to be more but trying out the cheap and easy thing first is best when its on your dime. You never know. It may just solve the problem. And if not, you've still run cleaner through the fuel system and on an 8 year old vehicle, that's not a bad thing to do anyway.
 
#20 ·
Here is what I am facing now, I replaced the injector put everything back together and the engine started right up... But tons of smoke out of the exhaust and because of a exhaust leak I noticed raw fuel seepage. Did I not do something I should have, I am so frustrated and have no clue what to do now
 
#27 ·
Can you drive it? I would suggest running it to Autozone or someplace and have them clear the codes. While there, pick up a new set of spark plugs and change them right in the parking lot. See if the problem rears its head again.

You could check the resistance on the plug wires too in order to see if you're getting adequate spark.

I wish I were right there with you to look at it. Nothing beats seeing stuff in person.
 
#28 ·
Let me say I am not a pro mechanic either, nor do I have a large wallet that is why I am trying to fix this myself. I replaced the spark plug on the #1 cyl but still have the same problem. There is spark at the coil and brand new plug wires. Could the new injector be doing to much fuel? And I REALLY AM THANKFUL for all the advice everyone is giving me.
 
#30 ·
I would have removed all of of the injectors and had them cleaned and flow tested, vs. replacing one injector. It makes for a much better job, since they will all be flowing at the same rate. The injector you replaced could be bad too, it happens. Having the set or injectors cleaned and flow tested assures you that they are all working properly and up to spec.

I don't want to violate board rules but I have a friend who runs a fuel injector cleaning service, and might be able to advise you. PM me for details and I can give you more info if you're interested.
 
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