Open loop/ Closed loop?
Junior Member
Joined: May 2008
Posts: 15,016
Likes: 11
From: +34° 25' 35.67", -81° 21' 12.04"
Year: 1993
Engine: 4.0
I wouldn't pull the head off for that either.
It has to be something simple.
You may have already said this but...
how do you know it's only cylinder 4? Code?
When you start it and it begins to run rough... how long does it run rough? Until you cut it off? Does it clear back up over time without cutting it off?
It has to be something simple.
You may have already said this but...
how do you know it's only cylinder 4? Code?
When you start it and it begins to run rough... how long does it run rough? Until you cut it off? Does it clear back up over time without cutting it off?
Thread Starter
Member
Joined: Jun 2012
Posts: 116
Likes: 0
From: Apollo, Pa
Year: 2000
Model: Cherokee
I wouldn't pull the head off for that either.
It has to be something simple.
You may have already said this but...
how do you know it's only cylinder 4? Code?
When you start it and it begins to run rough... how long does it run rough? Until you cut it off? Does it clear back up over time without cutting it off?
It has to be something simple.
You may have already said this but...
how do you know it's only cylinder 4? Code?
When you start it and it begins to run rough... how long does it run rough? Until you cut it off? Does it clear back up over time without cutting it off?
always get p0304 code and yes if I let it sit there and idle for awhile you can hear it clear up, but i always just start it up, let oil presure biuld up then im off.
one of my last post about open/ closed loop and the sensors compensating for some issue seams more and more true because i found out the it goes back in forth from open to closed loop and sometime the cel will flash on some driving conditions when it flips back to open but my driving changes and it flips to closed before it cut the #4 injector to go back to limp mode.
Junior Member
Joined: May 2008
Posts: 15,016
Likes: 11
From: +34° 25' 35.67", -81° 21' 12.04"
Year: 1993
Engine: 4.0
always get p0304 code and yes if I let it sit there and idle for awhile you can hear it clear up, but i always just start it up, let oil presure biuld up then im off.
one of my last post about open/ closed loop and the sensors compensating for some issue seams more and more true because i found out the it goes back in forth from open to closed loop and sometime the cel will flash on some driving conditions when it flips back to open but my driving changes and it flips to closed before it cut the #4 injector to go back to limp mode.
one of my last post about open/ closed loop and the sensors compensating for some issue seams more and more true because i found out the it goes back in forth from open to closed loop and sometime the cel will flash on some driving conditions when it flips back to open but my driving changes and it flips to closed before it cut the #4 injector to go back to limp mode.
1 minute? 10 minutes?
Reason I ask I had a similar issue. It ran like crap for a minute or so when you first start it. Once it cleared up it ran great for the rest of the trip. It only ran bad when you started it up if it was cold. A warm start didn't cause the issue.
Upstream O2 sensor fixed the issue. You've already replaced them tho...
Junior Member
Joined: May 2008
Posts: 15,016
Likes: 11
From: +34° 25' 35.67", -81° 21' 12.04"
Year: 1993
Engine: 4.0
always get p0304 code and yes if I let it sit there and idle for awhile you can hear it clear up, but i always just start it up, let oil presure biuld up then im off.
one of my last post about open/ closed loop and the sensors compensating for some issue seams more and more true because i found out the it goes back in forth from open to closed loop and sometime the cel will flash on some driving conditions when it flips back to open but my driving changes and it flips to closed before it cut the #4 injector to go back to limp mode.
one of my last post about open/ closed loop and the sensors compensating for some issue seams more and more true because i found out the it goes back in forth from open to closed loop and sometime the cel will flash on some driving conditions when it flips back to open but my driving changes and it flips to closed before it cut the #4 injector to go back to limp mode.
1 minute? 10 minutes?
Reason I ask I had a similar issue. It ran like crap for a minute or so when you first start it. Once it cleared up it ran great for the rest of the trip. It only ran bad when you started it up if it was cold. A warm start didn't cause the issue.
Upstream O2 sensor fixed the issue. You've already replaced them tho...
It's just strange that it's always Cylinder 4.
Seasoned Member
Joined: Jun 2012
Posts: 427
Likes: 0
From: Ronceverte WV
Year: 1998
Model: Cherokee
Engine: 4.0 I6
I think that was directed towards all of us.
Did you check the gap on the spark plug? I had a misfire in my XJ and I replaced the plugs,wires,cap&rotor and it cleared up for me. But you don't have wires,cap&rotor idk.
Just throwing check the gap out there. .035 If I remember correctly.
Did you check the gap on the spark plug? I had a misfire in my XJ and I replaced the plugs,wires,cap&rotor and it cleared up for me. But you don't have wires,cap&rotor idk.
Just throwing check the gap out there. .035 If I remember correctly.
Newbie
Joined: Oct 2019
Posts: 19
Likes: 0
Year: 1993
Model: Cherokee (XJ)
Engine: 4.0
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