Running Poorly and P0303 Error Code

A

AZ Curly

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As I am new to this forum and to all the new computer stuff related to Jeeps I have a general question that may have been addressed. I have a 2006 Jeep LJ with a little over 190,
000 miles. Recently I started getting engine codes and poor performance.

It started with codes for the O2 sensors, then a code for a bad cat. I did the sensors but not the cats. Then the crank and cam sensor, those were replaced. Now after reading some here, code P0303.

Prior to the code I began to loose power at freeway speeds. After some research I was told the cats may be plugged. With the loss of power I got the new P0303 code which some attributed to increased heat. Well, I do live in Phoenix and temps are well over 100 now.

With the cat isqsue would that increase the temp causing the code. When its first started it runs fine. I read about the Service Bulletin regarding a heat shield.

My remedy now was I ordered a direct fit cat system and will see if that affects it. Also I did have new plugs, coils, radiator, water pump and so on.

note: the head gasket seems to be fine, no steam in exhaust or oil in radiator.
 
The heat of phoenix doesn't have any affect on the heat of the cat, even though it seems like Phoenix is as hot as a cat sometimes.
It looks like p0303 is a number 3 plug misfire?

I am not sure where you got the cat idea, but it looks like there is a Technical Service Bulletin for your issue.
You might try this before replacing your cat. Probably much cheaper.

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

Looks like this TSB doesn't actually apply to your year. I will do some more poking around.

Welcome to the forum from Chandler.
 
Last edited:
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The cat did have a code prior to the 0303, and speaking to a couple jeep shops the consensus was restricted or blocked cats... I figured at this point with the summer temps and back pressure from cats related to heat I would try doing new cats and the heat shielding. There is 190k on engine so, except for the recent new items, its all original equipment.
 
ac_ said:
The heat of phoenix doesn't have any affect on the heat of the cat, even though it seems like Phoenix is as hot as a cat sometimes.
It looks like p0303 is a number 3 plug misfire?

I am not sure where you got the cat idea, but it looks like there is a Technical Service Bulletin for your issue.
You might try this before replacing your cat. Probably much cheaper.

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

Looks like this TSB doesn't actually apply to your year. I will do some more poking around.

Welcome to the forum from Chandler.
Click to expand...


Thanks
 
AZ Curly said:
The cat did have a code prior to the 0303, and speaking to a couple jeep shops the consensus was restricted or blocked cats... I figured at this point with the summer temps and back pressure from cats related to heat I would try doing new cats and the heat shielding. There is 190k on engine so, except for the recent new items, its all original equipment.
Click to expand...
Dont quote me on this it gets deeper than I can explain.
The metal used in the catalytic converter only works when it gets really hot. So at start up it takes it a while for the system to even start to work. Also the O2 sensor is also heat activated (with some electrical). That is why newer 02 sensors have heaters built in.
The outside heat wont affect the cat. Per say.

*********important ********
BTW. When you change the cat do not throw them away take you receipt and the cat to a recycling center. They will pay you for them. Anywhere from 10 to 40 bucks Depending on how much metal is left. But you have to have a receipt for new cats to sell your old ones. (Stops stealing and people removing theirs for cash)
 
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Boinked said:
Dont quote me on this it gets deeper than I can explain.
The metal used in the catalytic converter only works when it gets really hot. So at start up it takes it a while for the system to even start to work. Also the O2 sensor is also heat activated (with some electrical). That is why newer 02 sensors have heaters built in.
The outside heat wont affect the cat. Per say.

*********important ********
BTW. When you change the cat do not throw them away take you receipt and the cat to a recycling center. They will pay you for them. Anywhere from 10 to 40 bucks Depending on how much metal is left. But you have to have a receipt for new cats to sell your old ones. (Stops stealing and people removing theirs for cash)
Click to expand...

You are correct. About the 02's with heaters. The heaters are there to fool the computer to let it think that the exhaust is hotter than it actually is during warm up. They only heat for seconds on cold starts.
 
AZ Curly said:
As I am new to this forum and to all the new computer stuff related to Jeeps I have a general question that may have been addressed. I have a 2006 Jeep LJ with a little over 190,
000 miles. Recently I started getting engine codes and poor performance.

It started with codes for the O2 sensors, then a code for a bad cat. I did the sensors but not the cats. Then the crank and cam sensor, those were replaced. Now after reading some here, code P0303.

Prior to the code I began to loose power at freeway speeds. After some research I was told the cats may be plugged. With the loss of power I got the new P0303 code which some attributed to increased heat. Well, I do live in Phoenix and temps are well over 100 now.

With the cat isqsue would that increase the temp causing the code. When its first started it runs fine. I read about the Service Bulletin regarding a heat shield.

My remedy now was I ordered a direct fit cat system and will see if that affects it. Also I did have new plugs, coils, radiator, water pump and so on.

note: the head gasket seems to be fine, no steam in exhaust or oil in radiator.
Click to expand...

Ok, it's fixed...I obtained a Flowmaster Direct Fit Cat set and a Thrush performance muffler. It's in and it fixed the problems. More performance, a deeper sound and better mileage.

A downstream O2 sensor which I had replaced was severely damaged from pieces of the cat which did completely plug 1,2,3 exhaust pipe. It did create a higher heat level causing the code P0303.

The jeep runs great, next project will be the ATK 4.7. With over 190,000 on original engine its time.

My thoughts are to beef up the transmission and transfer case and I will be seeking thoughts from ya'll
 
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