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  #1  
Old November 24th, 2016, 08:52
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XJensen XJensen is offline
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Misfire cylinder 5

I have had a misfire on cylinder 5 and swapped out the coil. That seemed to help a lot but is getting worse again and just threw another code, I still need to scan the new code....

Just wanted to start a thread and get ideas rolling. I need this fixed soon to pass smog...
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Old November 24th, 2016, 08:53
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Re: Misfire cylinder 5

2001 xj hesco 4.5 Ford injectors everything else stock
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Old November 24th, 2016, 10:08
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Re: Misfire cylinder 5

How are your spark plugs? Are you feeling a jerking when it misfires?
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Old November 24th, 2016, 10:36
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Re: Misfire cylinder 5

What codes are you seeing ?

What brand/type spark plugs are installed ?

Have tested the injectors and injector wire harness ?
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Old November 24th, 2016, 10:46
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Re: Misfire cylinder 5

Fuel injector may be the problem mine keeps giving misfire on #2 changed that plug and wire keeps coming back .
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  #6  
Old November 24th, 2016, 11:54
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Re: Misfire cylinder 5

Not home now and will check the latest code this weekend. In the past it has been the random misfire and cylinder 5 misfire.

I figured I will swap in new plugs while I was at it. What brand do you guys recommend?

How can I test the injectors and the injector wires?
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Old November 24th, 2016, 12:26
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Re: Misfire cylinder 5

Random misfire could be from a bad crank sensor. It might be failing
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  #8  
Old November 24th, 2016, 13:40
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Re: Misfire cylinder 5

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Originally Posted by 90xj06 View Post
Random misfire could be from a bad crank sensor. It might be failing
Thanks I thought I heard something about that too.bany way to test it?

It this a sensor best to get from Mopar?
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Old November 24th, 2016, 19:49
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Re: Misfire cylinder 5

First things first. Do a compression test. What do the plugs look like?
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  #10  
Old November 24th, 2016, 21:27
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Re: Misfire cylinder 5

When you get a cylinder misfire, the ecu will always throw a P0300 too.

Now, a single cylinder misfire is easy to diagnose. It's either fuel, spark, or compression. Start with a simole compression test. Next, move around the ignition components. Move the #5 spark plug to the #4 spot. Drive it, see if the misfire moves. (Side note, always always always use OEM spark plugs) Next, swap the coil between cylinders 4 & 5. If it didn't move, swap the injector between 4 & 5. At this point, you should have only moved stuff and not spent superfluous money. When the problem moves to another cylinder, that's the component to change out.
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Old November 25th, 2016, 05:44
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Re: Misfire cylinder 5

Always buy genuine Jeep engine sensors. Regardless, the symptoms described do not suggest a Crankshaft Position Sensor (CPS) problem.


The Jeep 4.0 L runs best on basic Champion spark plugs. The 2000-01 runs well on those too, but runs a bit better on AutoLite APP-985. Confirm that the spark plug boots are not bunched up and that they are fully engaged on the spark plug body.

As suggested already, swap spark plugs first and injectors after a few days to see if the misfire follows either part.

Use your volts/ohms multi-meter to test the injector ohms, and to test the injector wire circuit continuity as you wiggle the wires.
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Last edited by Tim_MN; November 25th, 2016 at 05:49.
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  #12  
Old November 25th, 2016, 22:16
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Re: Misfire cylinder 5

Quote:
Originally Posted by old_man View Post
First things first. Do a compression test. What do the plugs look like?
Will do
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  #13  
Old May 14th, 2019, 10:59
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Re: Misfire cylinder 5

OK this has been a long while but is still an issue. I rolled the dice last I posted and passed SMOG then promptly blew up the front end on the first trip out. Front is finally all fixed up but I am still having trouble with the misfire in cyl #5.

I have completed the follow tests
compression, roughly 165 across all cyl
adjusted the CPS with a toothpick, it was slightly off
Fuel pressure - steady 45lbs
spark - seamed good
injectors - swapped and still an issue with #5
injector wires - pulse seamed normal
intake leaks - used carb cleaner and could not find anything
Cleaned up all grounds
Wrapped injectors with lava mat
Bought a new heat shield for the exhausts manifold - here later this week

I will test it out again this week but once the CPS was adjusted is seemed to run great cold the misfire when hot. I also bought the Torque Pro app but cant seem to connect to the Mode $06 misfire data. Any help there? I believe PID 06A6 data point C & B for the average and cycle counts.

Once warm would leave me to believe O2 sensor but would that cause an issue with only one cyl?
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  #14  
Old May 14th, 2019, 12:05
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Re: Misfire cylinder 5

What did the plugs look like? Was #5 the same as the others?

Since it was mentioned about swapping the coils, I guess it is a coil on cylinder setup. Is there a possibility somehow the coil drive got swapped sometime in the past. That would cause a similar problem.

From here, I would get a NOID light and see if you can detect any difference between cylinders. The same cylinder swap issue can happen on injectors as well. On a Renix, #5 and #6 leads are almost exactly the same length. Check the color codes with the manual.
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  #15  
Old May 14th, 2019, 19:08
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Re: Misfire cylinder 5

The plug looked a little discolored but not much different from the others. It still has the coil rail so no risk of switching those around.

I tested with a NOID and the pulse to the injectors all looked the same. If the plugs to 5 and 6 were switched wouldnt they both show a misfire? I dont think they are switched but will look
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