Another 2001 4.0 P0306 issue
11-15-2010 | 01:52 PM
#46
Member
Joined: May 2010
Posts: 155
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From: southlake, TX
Year: 1996 Sport
Model: Cherokee
Engine: 4.0L H.O.
hey Membrain... where in dfw are you? .... i skimmed through the thread and didn't see any mention of checking your cat! how old is the cat? ... sometimes, a misfire on the rear cylinder could be the result of a plugged/plugging up cat (i.e. cyl 6 is the one at the rear of the block), if all else seems fine ... and it sounds like you've looked at/changed everything! ...good luck!
11-16-2010 | 06:57 AM
#47
Thread Starter
Junior Member
Joined: Oct 2010
Posts: 31
Likes: 0
From: DFW
Year: 2001
Model: Cherokee
Engine: 4.0
Howdy! I'm in the Grand Prairie/Arlington area. Sorry, but I have 5 dogs... no cats... 
We haven't seen any Cat or O2 sensor codes yet. I do know that an ongoing/extended misfire could damage a cat but this cyl 6 misfire just started this summer. If the cat was plugging up then I think I'd also see conditions flagged on cyls 4 & 5, too.
We did replace the water pump in Nov 09 but everything has been fine until this misfire condition that just wont clear.
Last edited by membrain; 11-16-2010 at 07:12 AM.
11-16-2010 | 11:49 AM
#49
Thread Starter
Junior Member
Joined: Oct 2010
Posts: 31
Likes: 0
From: DFW
Year: 2001
Model: Cherokee
Engine: 4.0
gonna try regapping plugs to .045 from OEM .035 first... and again resetting the computer... after this we have run out of options then will have to replace head after first of year... don't want to spend xmas money on a head just yet... still like the idea of doing the valve rotation just so I can say we tried that too. The #6 cyl compression value as compared to the others causes me some brain-pain.
If my son had a job we would just go trade it in on a new JK...
I didn't have these problems with my TJs...
My new JK is nice...
...
If my son had a job we would just go trade it in on a new JK...
I didn't have these problems with my TJs...
My new JK is nice...
...
Last edited by membrain; 11-16-2010 at 11:53 AM.
11-16-2010 | 11:55 AM
#50
Thread Starter
Junior Member
Joined: Oct 2010
Posts: 31
Likes: 0
From: DFW
Year: 2001
Model: Cherokee
Engine: 4.0
still in the search for it... but does anyone remember the post/threads that discussed a Tech Bulletin addressing where the computer code would not ever clear and therefore needed a reflash?
11-16-2010 | 12:50 PM
#51
Member
Joined: May 2010
Posts: 155
Likes: 0
From: southlake, TX
Year: 1996 Sport
Model: Cherokee
Engine: 4.0L H.O.
hey.... from my experience (i had an 87 cherokee as well) .... with the i6 (jeeps) and v6 (mercedes) .... i've had bad cats that i knew about (rattling a while), but no codes ... then, suddenly, no more rattling!, all's well ..... but, threw a misfire code on the rear cylinder (both i6 and v6 - the mercedes has four cats - two on each bank in series)!.... i cleared the code and still it came back ..... banged on the cat to dislodge the broken pieces and the misfire code did not reappear.... soon thereafter, i had the cat replaced and found out that the cat's innards, size of golf *****, had made their way to the muffler inlet, limiting the exhaust from exiting! ......
.... is the misfire random or on a regular basis? .... you can take out the o2 sensor before/after the cat to relieve pressure and see if that stops the misfire and to check if the cat or exhaust system is the culprit ... good luck!
.... is the misfire random or on a regular basis? .... you can take out the o2 sensor before/after the cat to relieve pressure and see if that stops the misfire and to check if the cat or exhaust system is the culprit ... good luck!
11-16-2010 | 01:54 PM
#52
Thread Starter
Junior Member
Joined: Oct 2010
Posts: 31
Likes: 0
From: DFW
Year: 2001
Model: Cherokee
Engine: 4.0
hey.... from my experience (i had an 87 cherokee as well) .... with the i6 (jeeps) and v6 (mercedes) .... i've had bad cats that i knew about (rattling a while), but no codes ... then, suddenly, no more rattling!, all's well ..... but, threw a misfire code on the rear cylinder (both i6 and v6 - the mercedes has four cats - two on each bank in series)!.... i cleared the code and still it came back ..... banged on the cat to dislodge the broken pieces and the misfire code did not reappear.... soon thereafter, i had the cat replaced and found out that the cat's innards, size of golf *****, had made their way to the muffler inlet, limiting the exhaust from exiting! ......
.... is the misfire random or on a regular basis? .... you can take out the o2 sensor before/after the cat to relieve pressure and see if that stops the misfire and to check if the cat or exhaust system is the culprit ... good luck!
.... is the misfire random or on a regular basis? .... you can take out the o2 sensor before/after the cat to relieve pressure and see if that stops the misfire and to check if the cat or exhaust system is the culprit ... good luck!
11-25-2010 | 09:08 PM
#54
Member
Joined: Nov 2010
Posts: 141
Likes: 0
From: Indy
Year: 2000
Model: Cherokee
Engine: 4.0
why bother replacing the head with a 2000/2001 head?
they are known to be poor quality heads, they are known to warp and crack.
the '95 head is ported better, probably the same price, and is cast properly. sure, you have to make a bracket to hold the coil rail/packs, but it's gonna net more power, better mileage, and less chance for failure.
that said, don't drop $150 on gaskets. you need an intake/exhaust gasket ($13), head gasket ($20), head bolts ($36), and t-stat gasket ($3), and a GOOD rubber valve cover gasket (which is NOT included in the $150 gasket set....they include a cork one...)...that is $44.
so, you get the new head, and spend $90 or so on gaskets, and are less out of pocket.
you don't need to pull the fuel rail, sensors, or throttle body off the intake to do this job...
they are known to be poor quality heads, they are known to warp and crack.
the '95 head is ported better, probably the same price, and is cast properly. sure, you have to make a bracket to hold the coil rail/packs, but it's gonna net more power, better mileage, and less chance for failure.
that said, don't drop $150 on gaskets. you need an intake/exhaust gasket ($13), head gasket ($20), head bolts ($36), and t-stat gasket ($3), and a GOOD rubber valve cover gasket (which is NOT included in the $150 gasket set....they include a cork one...)...that is $44.
so, you get the new head, and spend $90 or so on gaskets, and are less out of pocket.
you don't need to pull the fuel rail, sensors, or throttle body off the intake to do this job...
http://www.oreillyauto.com/site/c/de...ead+gasket+set
Why would you want to run an old head...the late model heads flow better and make more power pluss the intake and exhaust manifolds flow better.
Port shape is more important then size....the late model heads have smaller ports but flow almost the same numbers....really helps make low end power.
O'Reilly sells the good late model head for around 450.00
11-29-2010 | 07:39 AM
#55
Thread Starter
Junior Member
Joined: Oct 2010
Posts: 31
Likes: 0
From: DFW
Year: 2001
Model: Cherokee
Engine: 4.0
I'll take a look at the O'reilly head again... but after having some issues with their other parts I am hesitant... O'reilly crankshaft position sensor problem, O'reilly MAP sensor hole size problem...
So, it looks like a head
replacement is in order.
No, we have not replaced the O2 sensors as none of the codes point in this direction. The fact that the compression for #6 cylinder is different from the others is the only outstanding pointer. Could be a burnt/bent valve... we won't know until we replace the head.
So, it looks like a head
replacement is in order.No, we have not replaced the O2 sensors as none of the codes point in this direction. The fact that the compression for #6 cylinder is different from the others is the only outstanding pointer. Could be a burnt/bent valve... we won't know until we replace the head.
11-29-2010 | 07:46 AM
#56
CF Veteran
Joined: Nov 2008
Posts: 2,003
Likes: 4
Year: 1987
Model: Cherokee
Engine: 4.0
the 136.00 set comes with the rubber valve cover gasket.
http://www.oreillyauto.com/site/c/de...ead+gasket+set
Why would you want to run an old head...the late model heads flow better and make more power pluss the intake and exhaust manifolds flow better.
Port shape is more important then size....the late model heads have smaller ports but flow almost the same numbers....really helps make low end power.
O'Reilly sells the good late model head for around 450.00
http://www.oreillyauto.com/site/c/de...ead+gasket+set
Why would you want to run an old head...the late model heads flow better and make more power pluss the intake and exhaust manifolds flow better.
Port shape is more important then size....the late model heads have smaller ports but flow almost the same numbers....really helps make low end power.
O'Reilly sells the good late model head for around 450.00
I run mid 90's heads. I run them because, unlike some people here, I can rebuild them myself without issue. if I can rebuild them myself, that means that ALL late model heads are junk to me. I can't trust an 0331 casting, and I really didn't like how my '98 and '97 performed, so I'll stick with the '95 casting, rebuild it myself, and be out the cost of a head gasket set.
12-05-2010 | 09:07 AM
#59
Thread Starter
Junior Member
Joined: Oct 2010
Posts: 31
Likes: 0
From: DFW
Year: 2001
Model: Cherokee
Engine: 4.0
New head is on and we haven't started the engine yet. After we reassembled the head we noticed the rocker arms are not centered over the tops of the valves... wtf? How do we adjust or fix this?
