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Cylinder 3 misfire (2001 Cherokee Sport)


 
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broooooooce
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Joined: 09 May 2009
Location: Little Rock, Arkansas, USA

PostPosted: Thu Jun 25, 2009 11:27 am    Post subject: Cylinder 3 misfire (2001 Cherokee Sport) Reply with quote

Hi.

Recently, my jeep has been extremely rough starting and this caused the engine light to come on so I went and got the code checked. Cylinder 3 misfire it said. Well, 3000 miles ago, I had changed the plugs myself (but not the coils or the coil assembly). Well, I just decided to make sure the thing was gapped correctly and it was and I wiped off a tiny bit of build up on the spark plug, put it back in. I only did this for cylinder 3. I disconnected/reconnected the battery to get rid of the engine light and it drove and started fine for a while until today when it started rough again and low and behold, same thing cylinder 3 misfire.

Autozone troubleshooting ticket based on my code says it's probably:

Ignition system fault - plugs/ignition wires/coil
Vacuum leak
Injector Fault
high or Low fuel pressure.

I haven't changed the coils or the coil assembly thing. But it seems like the coils are just springs inside of a rubber "boot" and it strikes me as unlikely that these suddenly just failed? Who knows though.

150,000 miles on it and it idles just a tiny bit rough, but always has.

I don't know jack about vacuum leaks or how that would tie into things.

Could it be the injector on the 3rd cylinder?

What does high or low fuel pressure mean?

I would be very grateful if someone would suggest to me the most cost-effective path by which I can troubleshoot and eventually fix this.

Thanks,
Bruce
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broooooooce
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Joined: 09 May 2009
Location: Little Rock, Arkansas, USA

PostPosted: Sun Jun 28, 2009 1:36 pm    Post subject: Reply with quote

replaced coil pack and it ran fine for a couple days and then the light comes back on today. Get the code checked and its P0118 - Engine coolant temperature sensor input above maximum acceptable voltage. Also, the temp gauge goes out intermittently. I am fairly sure that this sensor may be the culprit of the misfires and stuff because it tells how rich a fuel mixture to shoot into the cylinders (I think....)

Will replace it tomorrow and report my results back here.

Bruce
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broooooooce
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Joined: 09 May 2009
Location: Little Rock, Arkansas, USA

PostPosted: Mon Jun 29, 2009 8:03 pm    Post subject: Reply with quote

with the new coil pack, my oil pressure is higher (?!) I don't know how or why but it would sit between 10 and 40 on the gauge usually and now it tends to be 10-50 but mostly above 30.

It also drives a LITTLE different in an unexplainable way, it just feels a bit different--not better, but not necessarily worse.

So far so good, the engine light actually went off of its own accord just before I changed the coolant temp sensor and so far everything is ahite.
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Cherokeeper
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Joined: 02 Mar 2009
Location: St. Paul, MN

PostPosted: Thu Jul 02, 2009 9:45 am    Post subject: Reply with quote

Broooooooooooooooce:

I replied to an OLD OLD post that you had posted to.
Hopefully it will help you answer the question of rough starts when hot.
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