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Unread 03-07-2013, 09:30 PM   #1
Sweetjackal
Registered User
1999 XJ Cherokee 
 
Join Date: Dec 2007
Location: St. Pete, FL
Posts: 161
4.7 Misfire P0305

Basic info
4.7
135k miles
No known overheating issues
I have only owned this Jeep for 9 months, have only driven it 6k miles since

Problem
2 days ago parked it, started it 3hrs later to a really rough idle. Even under load you could feel the misfire. Drove for 10 mins cylinder fire returend to normal, once normal operating temp was reached. It has been this way for the last 72hrs.

Rough idle, feel the misfire until at operating temp... Then runs normal.
on day 2 it threw a code, cylinder 5 misfire P0305
Searching all over the forums everyone goes through the normal checks... Plugs, coil pack, injectors, compression.
I have done none so far, because i still cannot figure out why it misfires until it reaches temp... then STOPS and runs normal.
Any of the traditional culprits listed abouve would be present no matter the temp or duration of use. A faulty coil pack will misfire from ignition on to ignition off... and like wise for the other components.

Is the PCM shutting down that cylinder to correct the timing/spark/fire?

Does the issue correct itself with heat... i.e. explanding valve seat/seal, vaccume hose leak, et all.

Faulty CPS?

Any thoughts or input would be accepted.
I already understand the spark/coil/injecotr troubleshooting tips and plan to try those this weekend, i aldready expect the issue to persist.

I am more concerned with why it stops at temp and possible valve/head issues.

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99 XJ Classic - SOLD :(

00 WJ Limited - 4.7L Quadra-Crap, 3" IRO lift kit, JK Sahara 32's. Urban Wheeler / Daily Driver
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Unread 03-08-2013, 04:38 PM   #2
speedjunky1
Registered User
2000 WJ 
 
Join Date: Nov 2011
Location: breinigsville, pa
Posts: 96
had the same problem. Replaced the TPS and cleaned the IAC.
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Unread 03-08-2013, 05:36 PM   #3
WJEEPSMASS
Registered User
2003 WJ 
 
Join Date: Feb 2013
Location: Boston, MA
Posts: 80
Bad plug, cold plug. head warms up expands misfire goes away. Once the PCM detects operating temp PCM goes from open loop to closed loop... Is your check engine blinking?
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