CEL - P0302
07-31-2015, 12:52 PM
#1
Newbie
Thread Starter
CEL - P0302
Hey guys, i picked up an overheated one owner 2000 XJ recently. Previous owner claimed it has been parked since it over heated. Getting a cylinder 2 misfire code.
What I Have Done
The cooling system was REALLY clogged. I did about 10 flushes, replaced themostat, hoses, and radiator. This fixed the cooling issues.
I then replaced the head gasket. The hole was right next to cylinder 2. I figured this would solve the problem, but it did not. I also cleaned up the head and did a visual inspection and didnt see anything.
I then moved on and did the neon fuel injector swap to rule out fuel. Nothing.
I have also tried both champion and now NGK plugs.
I have put 2 tanks with cleaner through it
What I Still Need To Do?
Get a compression tester and test again.
I have a leak down tester, but not sure how to determine TDC
Replace coil pack? (i might swap it with my TJs)
Thoughts?
I have driven it probably 800 miles. Does not overheat, and does not feel to lack power (feels like more power than my TJ!). It does sound a bit rougher perhaps under 2k RPM, but i also have the exhaust chopped at the downstream o2. Idle needle is ~700 rpm, with a minuscule bobble.
What do you guys think? Any help greatly appreciated
What I Have Done
The cooling system was REALLY clogged. I did about 10 flushes, replaced themostat, hoses, and radiator. This fixed the cooling issues.
I then replaced the head gasket. The hole was right next to cylinder 2. I figured this would solve the problem, but it did not. I also cleaned up the head and did a visual inspection and didnt see anything.
I then moved on and did the neon fuel injector swap to rule out fuel. Nothing.
I have also tried both champion and now NGK plugs.
I have put 2 tanks with cleaner through it
What I Still Need To Do?
Get a compression tester and test again.
I have a leak down tester, but not sure how to determine TDC
Replace coil pack? (i might swap it with my TJs)
Thoughts?
I have driven it probably 800 miles. Does not overheat, and does not feel to lack power (feels like more power than my TJ!). It does sound a bit rougher perhaps under 2k RPM, but i also have the exhaust chopped at the downstream o2. Idle needle is ~700 rpm, with a minuscule bobble.
What do you guys think? Any help greatly appreciated
Last edited by cdurth; 07-31-2015 at 12:56 PM.
07-31-2015, 12:56 PM
#3
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07-31-2015, 01:00 PM
#5
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07-31-2015, 01:26 PM
#6
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Join Date: Feb 2014
Location: Florida
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Year: 2000
Model: Cherokee(XJ)
Engine: Golen 4.6L
Not sure about your cylinder 2 misfire code, but regarding your overheating issues:
All 2000 and 2001 XJs came with the 0331 head that likes to crack between the #3 and #4 cylinders as a result of a casting flaw. If you search for "0331 head," you'll find lots of discussion about it. It sometimes does it for no reason at all, even on a well-maintained truck that has never been overheated. Overheating one is just asking for it to crack. Seems like we're now seeing three or four of these posts per month on the board where people are buying 2000 and 2001 XJs only to find the head is no good.
Sometimes (but not always) you can actually see the crack or see coolant weeping up by looking down into the oil filler hole. Sometimes they crack so that hot exhaust gas enters the cooling system and boils the water out of the coolant, leaving that red mud behind that sticks to everything. That stuff isn't rust. It's what's left behind when you boil water out of coolant, like a salt crust left behind if you boil seawater. That garbage not only clogs the radiator, but it will also eat a water pump in a matter of months. People overhaul their cooling system only to find it full of crud three months later because they didn't correct the source of the problem.
You can send off an oil sample to test for the presence of coolant. You can get a $50 kit to test for exhaust gas in your coolant system. You can do a compression test.
If you determine that the head is cracked, you can get a bolt-on replacement from Clearwater Cylinder Head that is not prone to cracking for about $450. Or you can replace it with a TUPY 0331 head from a later model 4.0L; the ones with "TUPY" cast into the top of the head between the #3 and #4 cylinders had the casting flaw corrected. Or you can rig up an earlier 0630 head, but it has different exhaust ports and no provision for the coil rail, so you have to rig some things up to make it work.
Personally, I would just plan to replace that head regardless of whether it's actually cracked, just for peace of mind.
All 2000 and 2001 XJs came with the 0331 head that likes to crack between the #3 and #4 cylinders as a result of a casting flaw. If you search for "0331 head," you'll find lots of discussion about it. It sometimes does it for no reason at all, even on a well-maintained truck that has never been overheated. Overheating one is just asking for it to crack. Seems like we're now seeing three or four of these posts per month on the board where people are buying 2000 and 2001 XJs only to find the head is no good.
Sometimes (but not always) you can actually see the crack or see coolant weeping up by looking down into the oil filler hole. Sometimes they crack so that hot exhaust gas enters the cooling system and boils the water out of the coolant, leaving that red mud behind that sticks to everything. That stuff isn't rust. It's what's left behind when you boil water out of coolant, like a salt crust left behind if you boil seawater. That garbage not only clogs the radiator, but it will also eat a water pump in a matter of months. People overhaul their cooling system only to find it full of crud three months later because they didn't correct the source of the problem.
You can send off an oil sample to test for the presence of coolant. You can get a $50 kit to test for exhaust gas in your coolant system. You can do a compression test.
If you determine that the head is cracked, you can get a bolt-on replacement from Clearwater Cylinder Head that is not prone to cracking for about $450. Or you can replace it with a TUPY 0331 head from a later model 4.0L; the ones with "TUPY" cast into the top of the head between the #3 and #4 cylinders had the casting flaw corrected. Or you can rig up an earlier 0630 head, but it has different exhaust ports and no provision for the coil rail, so you have to rig some things up to make it work.
Personally, I would just plan to replace that head regardless of whether it's actually cracked, just for peace of mind.
07-31-2015, 01:33 PM
#7
Newbie
Thread Starter
Not sure about your cylinder 2 misfire code, but regarding your overheating issues:
All 2000 and 2001 XJs came with the 0331 head that likes to crack between the #3 and #4 cylinders as a result of a casting flaw. If you search for "0331 head," you'll find lots of discussion about it. It sometimes does it for no reason at all, even on a well-maintained truck that has never been overheated. Overheating one is just asking for it to crack. Seems like we're now seeing three or four of these posts per month on the board where people are buying 2000 and 2001 XJs only to find the head is no good.
Sometimes (but not always) you can actually see the crack or see coolant weeping up by looking down into the oil filler hole. Sometimes they crack so that hot exhaust gas enters the cooling system and boils the water out of the coolant, leaving that red mud behind that sticks to everything. That stuff isn't rust. It's what's left behind when you boil water out of coolant, like a salt crust left behind if you boil seawater. That garbage not only clogs the radiator, but it will also eat a water pump in a matter of months. People overhaul their cooling system only to find it full of crud three months later because they didn't correct the source of the problem.
You can send off an oil sample to test for the presence of coolant. You can get a $50 kit to test for exhaust gas in your coolant system. You can do a compression test.
If you determine that the head is cracked, you can get a bolt-on replacement from Clearwater Cylinder Head that is not prone to cracking for about $450. Or you can replace it with a TUPY 0331 head from a later model 4.0L; the ones with "TUPY" cast into the top of the head between the #3 and #4 cylinders had the casting flaw corrected. Or you can rig up an earlier 0630 head, but it has different exhaust ports and no provision for the coil rail, so you have to rig some things up to make it work.
Personally, I would just plan to replace that head regardless of whether it's actually cracked, just for peace of mind.
All 2000 and 2001 XJs came with the 0331 head that likes to crack between the #3 and #4 cylinders as a result of a casting flaw. If you search for "0331 head," you'll find lots of discussion about it. It sometimes does it for no reason at all, even on a well-maintained truck that has never been overheated. Overheating one is just asking for it to crack. Seems like we're now seeing three or four of these posts per month on the board where people are buying 2000 and 2001 XJs only to find the head is no good.
Sometimes (but not always) you can actually see the crack or see coolant weeping up by looking down into the oil filler hole. Sometimes they crack so that hot exhaust gas enters the cooling system and boils the water out of the coolant, leaving that red mud behind that sticks to everything. That stuff isn't rust. It's what's left behind when you boil water out of coolant, like a salt crust left behind if you boil seawater. That garbage not only clogs the radiator, but it will also eat a water pump in a matter of months. People overhaul their cooling system only to find it full of crud three months later because they didn't correct the source of the problem.
You can send off an oil sample to test for the presence of coolant. You can get a $50 kit to test for exhaust gas in your coolant system. You can do a compression test.
If you determine that the head is cracked, you can get a bolt-on replacement from Clearwater Cylinder Head that is not prone to cracking for about $450. Or you can replace it with a TUPY 0331 head from a later model 4.0L; the ones with "TUPY" cast into the top of the head between the #3 and #4 cylinders had the casting flaw corrected. Or you can rig up an earlier 0630 head, but it has different exhaust ports and no provision for the coil rail, so you have to rig some things up to make it work.
Personally, I would just plan to replace that head regardless of whether it's actually cracked, just for peace of mind.
EDIT: overlooked your first sentence. Overheating issue seems to be resolved now
Last edited by cdurth; 07-31-2015 at 02:42 PM.
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