Open loop/ Closed loop?
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Joined: Jun 2012
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From: Apollo, Pa
Year: 2000
Model: Cherokee
Closed loop can be reached within seconds of motor start-up or it can be a minute or so after start-up.....kinda depends on a number of variables. A misfire is either a momentary no spark at the plug (for several reasons) or an momentary insufficient injector squirt of fuel (for whatever reason).
Again, closed loop" is simply the O2 sensor joining in with the PCM and motor/other sensors. I wouldn't think closed loop has anything to do with a specific cylinder misfire (no spark/no fuel).
Is it always cyl #4? May want to revisit post #4. I think I remember tj suggesting a while back that if all of the ignition electrical is good (but still getting a misfire at #4), try switching injectors #3 and #4 or #4 and #5 to see if the misfire moves to #3 or #5. If the misfire moves, it's probably an injector, if it doesn't move, probably something causing no spark at #4.
Hope I didn't mis-quote tj.
Again, closed loop" is simply the O2 sensor joining in with the PCM and motor/other sensors. I wouldn't think closed loop has anything to do with a specific cylinder misfire (no spark/no fuel).
Is it always cyl #4? May want to revisit post #4. I think I remember tj suggesting a while back that if all of the ignition electrical is good (but still getting a misfire at #4), try switching injectors #3 and #4 or #4 and #5 to see if the misfire moves to #3 or #5. If the misfire moves, it's probably an injector, if it doesn't move, probably something causing no spark at #4.
Hope I didn't mis-quote tj.
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Joined: Jun 2012
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From: Apollo, Pa
Year: 2000
Model: Cherokee
No mention of checking under the valve cover.Check the casting # on the head.
Read the plug out of cyl #4. White, Black or Tan. Do you smell gas or coolant when you remove the plug.
It's only happening on one cylinder, so trouble shoot the one cylinder.
Open or Closed Loop shouldn't make any difference for just one cylinder.
I think valves or head.
Read the plug out of cyl #4. White, Black or Tan. Do you smell gas or coolant when you remove the plug.
It's only happening on one cylinder, so trouble shoot the one cylinder.
Open or Closed Loop shouldn't make any difference for just one cylinder.
I think valves or head.
CF Veteran
Joined: Apr 2012
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From: Wisconsin
Model: Cherokee
If the ECM counts too many misfires from a cylinder, it shuts the fuel off to that cylinder to avoid damaging the cat with raw gas. Re-starting the engine resets it.
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Joined: Jun 2012
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From: Apollo, Pa
Year: 2000
Model: Cherokee
The coil rail has 3 coils on it, each controlling 2 cylinders so its not likely that only one would screw up from a bad coil, but the one that was on it was a year old and I exchaged it for a new one, no help, but thanks
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From: Ringsted
Year: 1997
Model: Cherokee
Engine: 4.0 L
i have seen several ecu produce such a problem.
when it gets hot, it fails to activate the injector.
to test it, hook up a testlight on #4 injector and see if it stops firing when the misfired happens.
if so you either have some bad wiring or a bad ecu.
good luck with it
when it gets hot, it fails to activate the injector.
to test it, hook up a testlight on #4 injector and see if it stops firing when the misfired happens.
if so you either have some bad wiring or a bad ecu.
good luck with it
Thread Starter
Member
Joined: Jun 2012
Posts: 116
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From: Apollo, Pa
Year: 2000
Model: Cherokee
i have seen several ecu produce such a problem.
when it gets hot, it fails to activate the injector.
to test it, hook up a testlight on #4 injector and see if it stops firing when the misfired happens.
if so you either have some bad wiring or a bad ecu.
good luck with it
when it gets hot, it fails to activate the injector.
to test it, hook up a testlight on #4 injector and see if it stops firing when the misfired happens.
if so you either have some bad wiring or a bad ecu.
good luck with it
CF Veteran
Joined: Apr 2012
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From: Wisconsin
Model: Cherokee
Man, what an oddball thing. At this point I'd be tempted to check the continuity from the ECU to injector plug #4 while shaking the wiring harness, and the injector connector itself.
Maybe a leakdown test too to compare that cylinder against the others.
Maybe a leakdown test too to compare that cylinder against the others.
Thread Starter
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Joined: Jun 2012
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From: Apollo, Pa
Year: 2000
Model: Cherokee
Now I have a thought about the open loop closed loop. It seams like my jeep runs a little rough apon start up which would be in open loop, and i have been told that if the ecu sees a misfire it will prevent it from going to closed loop. So whats to so I dont have a crack in the intake or a bad valve or something that is making it miss and when I shut it off and resart, it goes straight to closed loop and the sensors are compensating for the root issue of a bad valve or crack somewhere?
All of this misfire issue started the day after I drove it 3.5 hrs in 95 degree weather, it never overheated or went above 210, but thats when it started
All of this misfire issue started the day after I drove it 3.5 hrs in 95 degree weather, it never overheated or went above 210, but thats when it started
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Joined: Nov 2010
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From: Salt Lake City, Utah
Year: 90
Model: Cherokee
I believe all possibilities must be eliminated to determine the actual cause.
0331 heads are known to be defective. So why not suspect it.
At this point in the troubleshooting/diagnosis the only part not closely inspected is the 0331 head.
It may completely improbable, but also may be the cause.
0331 heads are known to be defective. So why not suspect it.
At this point in the troubleshooting/diagnosis the only part not closely inspected is the 0331 head.
It may completely improbable, but also may be the cause.
Thread Starter
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Joined: Jun 2012
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From: Apollo, Pa
Year: 2000
Model: Cherokee
I believe all possibilities must be eliminated to determine the actual cause.
0331 heads are known to be defective. So why not suspect it.
At this point in the troubleshooting/diagnosis the only part not closely inspected is the 0331 head.
It may completely improbable, but also may be the cause.
0331 heads are known to be defective. So why not suspect it.
At this point in the troubleshooting/diagnosis the only part not closely inspected is the 0331 head.
It may completely improbable, but also may be the cause.
Yes I understand that it may be a cracked head but i have no plans on riping it off just to eliminate that possibility, ill just keep shutting it off till i can figure it out. Thanks for the input thou.