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Rockridge 4WD IS Taking Zone Offroad Suspension Lift Kits ZONE 4.25" combo lift for TJ available at Rockridge4wG2 Disc Brake Conversion Kit for Jeep Wrangler YJ TJ LJ Ch

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Unread 08-05-2014, 09:18 AM   #1
realvc
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1994 YJ Wrangler 
 
Join Date: Jul 2014
Location: Lake Norrell, Arkansas
Posts: 20
Sick Jeep

I've been reading a lot of threads trying to find out how to get my YJ running like it should.
I have found a lot of good information but I still need help.

I have 1994 2.5 that runs fine when cold.
When it is warmed up it runs ok at low rpms but when you need to go up a hill or get the rpms up to around 2500- 3000 like for passing gear it bogs down and if I keep on the gas it will continue to bog and will backfire.

It shows codes of 12, 13, 33, and 55.

The MAP sensor checks out with the vacuum test and the voltage test as described in some threads threads. Engine vacuum checks good too.

The vacuum lines are all in place.

The loss of power in the higher rpms like when passing gearing is needed the it is acting reminds me of when a catilytic converter or the exhaust is stopped up but there is not one on this jeep.

What happens when an O2 sensor is bad?
It seems like my jeep runs like it should until it is good and warmed up for several miles and or several minutes then the bogging starts up.
It will still run fine in the lower rpms and starts and idles just fine.

The plugs, wires, dist, cap and rotor were all changed and it was running great until this bogging started.

Intake gasket checks good.

Thanks for any help.

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Unread 08-05-2014, 09:37 AM   #2
grandboost98
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1989 YJ Wrangler 
 
Join Date: Aug 2010
Location: Durham/East Haven, CT
Posts: 3,224
Sounds like what I was experiencing a month ago. New fuel filter solved the problem for me
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Unread 08-05-2014, 10:01 AM   #3
Fozzybear42
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1993 YJ Wrangler 
 
Join Date: Jul 2012
Location: Englewood, Colorado
Posts: 234
+1 for fuel related. Mine was fairly similar although on mine it did it constantly. Ended up being a clogged fuel pump, but fuel filter could be it too. Go rent a fuel pressure tester from the parts store, and make sure you are seeing what happens to the pressure when the stumble happens. Personally, I just pulled the hood off and taped the gauge to my windshield.
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Unread 08-05-2014, 10:10 AM   #4
realvc
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1994 YJ Wrangler 
 
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Location: Lake Norrell, Arkansas
Posts: 20
Thanks for the heads up on fuel filter.
The fuel filter was changed not too long ago as in less than 500 miles.
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Unread 08-05-2014, 10:13 AM   #5
realvc
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I will follow up on the fuel pressure test.
Thanks
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Unread 08-05-2014, 11:25 AM   #6
Que89YJ
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1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 15,653
Check the fuel pressure first. If you don't have any luck then:
The map sensor fault needs to be cleared by disconnecting the battery for 10 sec.
It sounds like you have a meter which is good news. You need to check the ambient air temp sensor and if you have not replaced the O2 sensor, do it. The fuel can be an issue still but the cold/warm usually points to an issue with the O2 sensor.
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Unread 08-05-2014, 02:54 PM   #7
realvc
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1994 YJ Wrangler 
 
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Location: Lake Norrell, Arkansas
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Quote:
Originally Posted by Que89YJ View Post
Check the fuel pressure first. If you don't have any luck then:
The map sensor fault needs to be cleared by disconnecting the battery for 10 sec.
It sounds like you have a meter which is good news. You need to check the ambient air temp sensor and if you have not replaced the O2 sensor, do it. The fuel can be an issue still but the cold/warm usually points to an issue with the O2 sensor.
Fuel pressure checked out 40 with vacuum line removed and blocked off and 31 with the vacuum line hooked up.

I'll go a head and replace the O2 sensor now and then check the air temp sensor.

Thanks again
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Unread 08-05-2014, 05:06 PM   #8
realvc
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1994 YJ Wrangler 
 
Join Date: Jul 2014
Location: Lake Norrell, Arkansas
Posts: 20
Replaced the O2 sensor and there is no change.

Still bogs down when down shifting and trying to increase the rpms. When it is cold it will down shift and the rpms will go up past 4000. Then as it gets warmer the rpms decrease and bogs down when it down shifts to passing gear or downshifts for going up a hill. When it bogs down and you keep on the gas it will back fire.

Still need to check out the air temp sensor.
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Unread 08-05-2014, 05:15 PM   #9
Que89YJ
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Fuel pressure first. The air temp sensor is easy to check with a meter. Clear the codes.
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Unread 08-05-2014, 06:17 PM   #10
Luuca
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OK, ok... I'll say it.

Please fill out your Jeep's Profile here on the forums. It helps us all diagnose and learn from the issues you are having.

Welcome to the forum.
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05 LJ Rubicon "Ghost" 4" RE Lift 1" BL 33s
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Unread 08-05-2014, 06:27 PM   #11
realvc
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1994 YJ Wrangler 
 
Join Date: Jul 2014
Location: Lake Norrell, Arkansas
Posts: 20
Quote:
Originally Posted by Que89YJ View Post
Fuel pressure first. The air temp sensor is easy to check with a meter. Clear the codes.
I checked the fuel pressure and it was 40 with vacuum disconnected and 31 with vacuum connected.

After I checked the fuel pressure I replaced the O2 sensor and it made no difference.

The codes won't clear. When I disconnect the cables and reconnect them the same codes show up.

I will try leaving the cables off longer and see what happens.

I checked the air temp sensor with an ohm meter but I'm not sure if I did it right. I could get a reading of 365-390 but not close to 1000.

I pulled it out and it is coated with carbon.
I will pick one up tomorrow and see what happens.

The joy of old cars and getting to know them.
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Unread 08-05-2014, 06:31 PM   #12
Luuca
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Quote:
Originally Posted by realvc View Post
I checked the fuel pressure and it was 40 with vacuum disconnected and 31 with vacuum connected.

After I checked the fuel pressure I replaced the O2 sensor and it made no difference.

The codes won't clear. When I disconnect the cables and reconnect them the same codes show up.

I will try leaving the cables off longer and see what happens.

I checked the air temp sensor with an ohm meter but I'm not sure if I did it right. I could get a reading of 365-390 but not close to 1000.

I pulled it out and it is coated with carbon.
I will pick one up tomorrow and see what happens.

The joy of old cars and getting to know them.
Soon you will be diagnosing YJ issues based upon smell and sound young padawan. Que once diagnosed an electrical problem over the phone, on a plane, 3000 miles away just by a disturbance in the force - the guy with the problem was surprised when Que called him.
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05 LJ Rubicon "Ghost" 4" RE Lift 1" BL 33s
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Unread 08-05-2014, 06:41 PM   #13
realvc
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1994 YJ Wrangler 
 
Join Date: Jul 2014
Location: Lake Norrell, Arkansas
Posts: 20
Quote:
Originally Posted by Luuca View Post
OK, ok... I'll say it.

Please fill out your Jeep's Profile here on the forums. It helps us all diagnose and learn from the issues you are having.

Welcome to the forum.
I just filled it out as best I could with what I know about it.

I've had it on the lift now a couple of times but did not write down the transfer case name and numbers and don't know anything about the axles.
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Unread 08-05-2014, 10:13 PM   #14
DirtKar
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1993 YJ Wrangler 
 
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Location: Nor Cal Sierras
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Welcome to the forum.
You are currently in good hands. Que needs his own pay per minute number.
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Quote:
Originally Posted by Carlos14 View Post
What you see as not bad, and what I see as not bad, are two completely different not bads
YJOTM JULY 2014
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Unread 08-06-2014, 06:41 AM   #15
Que89YJ
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1989 YJ Wrangler 
 
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Location: Detroit, Michigan
Posts: 15,653
When you disconnect the battery the 13 code is still there? You should always see the 12,33,55 but not 13.
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