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Unread 01-11-2009, 09:23 PM   #1
fastbird
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check engine p0303

I replaced plugs and coils and still little mistfire when I start up my jeep.It only does whene engine is hot and last just 10 seconds.
Does anybody have any sugestions what should I check?
Thank you.

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Unread 01-12-2009, 05:02 AM   #2
tjwalker
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Gotta post your year/engine for best troubleshooting advice. My manual shows P0303 to be a cylinder 3 misfire. Depending on what year your XJ is, you may be suffering the "heat soak" problem. There is a technical service bulletin on it; here you go. I had it on my 99 and this was the fix. Does this match up with your vintage/symptoms?

TSB
1803103 - 4.0L ROUGH ENGINE IDLE AFTER RESTART FOLLOWING A HOT SOAK
Date: 09/05/03 (supercedes 1802702 dated 09/06/02)
Model Year(s): 1999-2004

Description: NOTE: This bulletin applies to vehicles equipped with a 4.0L engine. This bulletin involves the installation of a fuel injector insulator sleeve.

Details: Customers may describe a 20 to 30 second rough idle following the restart of a heat soaked engine. This condition may be most noticeable when the engine is restarted following a prior 10 to 20 minute heat soak in hot ambient conditions of approximately 32 C (90ºF) or higher. This condition may be consistent with short city stop-and-go driving trips and can be aggravated by the use of fuel with a high ethanol content. Depending upon various conditions a MIL may occur due to DTC P0303 - Cylinder #3 Misfire.

This condition may be caused by heat from the exhaust manifold that following engine shut down migrates to the area around injector #3 and causes fuel vapor to form within the injector. This in turn may cause a momentary misfire of cylinder #3 until the fuel vapor is cleared of injector #3. The insulator sleeve lowers the injector #3 temperature to a point below which the fuel will not normally vaporize.

If vehicle exhibits a rough idle, and if a misfire of cylinder #3 is observed following a 10 to 20 minute hot soak, perform the Repair Procedure.

Parts required:
56028371AA Ignition Wire Shield

Repair procedure:
1. Cut insulator sleeve, p/n 56028371AA, to make two (2) insulator sleeves about 25-30 mm (1 in.) in length. See diagram.
2. Install one sleeve around injector #3, with the slit on the upward facing side of the injector. Install the other sleeve with the slit on the downward facing side of the injector.
3. Confirm sleeve is flush to intake manifold surface around injector.
4. Check injector #3 wire and ensure that the injector is rotated to a 2 o'clock position.


TSB for the cold start rough idle and P0303 code: TSB 18-010-01
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Unread 01-12-2009, 01:11 PM   #3
fastbird
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Yes,that is my problem.
Where do I get ignition wire shield? Dealership?
Thanks
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Unread 01-12-2009, 04:38 PM   #4
tjwalker
It's the crank sensor!
 
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Yes, purchase the fix kit at any Jeep dealership; the part number is included in the TSB above. It's only a few bucks. Good luck and let us know if this fixes your symptoms!
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Unread 01-18-2012, 07:28 AM   #5
decarolis
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hey guys my jeep has the P0303 code if i clear the code i can drive all day with it, but when i get home and park it up in the garage.....go inside for about half hour to and hour and come back out as soon as i turn it on BOOM the P0303 code comes back

it sounds like im having the heat soak issue so i went and bought some heat sheild from my local auto parts store and covered the cylinder #3 fuel injector, but that hasent solved my issue.....what im thinking is maybe im covering the wrong part with my heat shield....are you ment to cover the wires from the fuel injector plug on cylinder #3 or...... a picture of someone who has done this TSB would help heaps as i havent been able to find one

if this doesnt work im gonna swap the connection plugs from the injectors to see if the missfire follows that plug....but if all else fails im lost atm

jeep in australia wants 50bucks for the heat sheild mentioned in the TSB which is the reason why i havent gone to them for that yet....i might just buy it over the internet but if its a simple fix with the heat sheild iv already got its worth a try

cheers

dan
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Unread 01-18-2012, 08:02 AM   #6
Oregon187
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http://www.jeepforum.com/forum/f9/he...04/index2.html

This thread has some good pics of it. There is also a pic in my build thread of what I did to mine. It seems to have worked for me so far but it's winter right now and the engine cools off pretty quickly anyway.
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Unread 01-18-2012, 08:24 AM   #7
XJnoob2012
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Fastbird,

I am having the same issue on my 2001 XJ. Bought the "fix" kit from the dealership...did not solve the problem. Added heat tape to cylinder 3...did not solve the problem. Insulated the entire fuel rail with heat tape...still not solved. Thinking about stepping up to the that heat sheath shown in Oregon187's posted link.

Just some food for thought, you might want to skip the items I did first and step straight to the beefy heat sheathing.
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Unread 01-18-2012, 09:09 AM   #8
decarolis
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Quote:
Originally Posted by Oregon187 View Post
http://www.jeepforum.com/forum/f9/he...04/index2.html

This thread has some good pics of it. There is also a pic in my build thread of what I did to mine. It seems to have worked for me so far but it's winter right now and the engine cools off pretty quickly anyway.
man you are a legend! i have my heat shield on the wrong spot so thats the reason why i still have the code appearing ill fix it tomorrow and see what comes from it
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Unread 01-18-2012, 09:52 AM   #9
Millermagic
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Shim the hood, add a switch to the e-fan.

I've been able to completely alleviate the problem in the summer. Shut the jeep off, flip the key to on, turn on fan for 30 seconds and then leave
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Unread 01-18-2012, 08:16 PM   #10
Oregon187
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Quote:
Originally Posted by decarolis

man you are a legend! i have my heat shield on the wrong spot so thats the reason why i still have the code appearing ill fix it tomorrow and see what comes from it
I've had the same problem and have done lots of research, which is how I found that thread. I'm not sure about the kit from the dealer that a lot of people talk about, I just used some heat shielding from AutoZone. Good luck, Mate.
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Unread 01-19-2012, 03:44 PM   #11
XJnoob2012
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Question for you guys and gals:

Anybody know if switching out the XJ injectors for mustang 5.0 injectors will solve the P0303 issue?
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Unread 01-19-2012, 04:42 PM   #12
Oregon187
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I doubt that it would help. It would improve your fuel flow but the heat soak issue results from the fuel in the injectors vaporizing. The injectors can't inject vapor so they sputter until the fumes are replaced by liquid fuel. The sputtering then creates the misfire in that cylinder. If you do change the injectors that woud be a good time to wrap them with heat shield.
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Unread 10-20-2012, 01:43 PM   #13
1rfninja
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I've got an "04 4.0. While I was towing a trailer (yesterday) up over a mountain the engine power dropped and the check engine light started flashing. I pulled over to check the engine code and it was a P0303. I was still 200 miles to my destination with no cell phone service so I continued on. It proceeded to get worse I had to go 20 -30 miles an hour up the hills/mountains. Before the trip my check engine light was on with the error code for the o2 censor but now that code does not come up only the P0303 error does. I took it out again today without the trailer attached and it has no power. If I put the pedal to the floor the rpm's rev up but it doesn't take off like it used to. Any help trouble shooting this would be much appreciated. I've read the other post on P0303 but my situation sounds a little different.
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Unread 10-20-2012, 04:24 PM   #14
tjwalker
It's the crank sensor!
 
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Quote:
Originally Posted by 1rfninja View Post
I've got an "04 4.0. While I was towing a trailer (yesterday) up over a mountain the engine power dropped and the check engine light started flashing. I pulled over to check the engine code and it was a P0303. I was still 200 miles to my destination with no cell phone service so I continued on. It proceeded to get worse I had to go 20 -30 miles an hour up the hills/mountains. Before the trip my check engine light was on with the error code for the o2 censor but now that code does not come up only the P0303 error does. I took it out again today without the trailer attached and it has no power. If I put the pedal to the floor the rpm's rev up but it doesn't take off like it used to. Any help trouble shooting this would be much appreciated. I've read the other post on P0303 but my situation sounds a little different.
Gotta start with basics:

1. Fresh plugs. Gapped to .035. I like NGK for your vintage

2. Even though it is not likely related, resolve the code that you had for a check engine light for oxygen sensor. If you would like to post the exact code, we can help you as codes for oxygen sensors can sometimes be difficult to interpret, not always the oxygen sensor itself. Never let a code go unresolved. It makes troubleshooting things more difficult the next time you have a symptom as you will wonder if it is related.
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Unread 10-27-2012, 07:12 AM   #15
1rfninja
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Quote:
Originally Posted by tjwalker View Post
Gotta start with basics:

1. Fresh plugs. Gapped to .035. I like NGK for your vintage

2. Even though it is not likely related, resolve the code that you had for a check engine light for oxygen sensor. If you would like to post the exact code, we can help you as codes for oxygen sensors can sometimes be difficult to interpret, not always the oxygen sensor itself. Never let a code go unresolved. It makes troubleshooting things more difficult the next time you have a symptom as you will wonder if it is related.
Did both with no success. The spark plugs I removed were in near perfect condition. 1 plug showed signs of running rich.
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