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Thread: Need Help Diagnosing Problem

  1. #1
    Join Date
    Jan 2014
    Location
    Maricopa
    Posts
    1,393

    Need Help Diagnosing Problem

    Basics: 2005 TJ Unlimited, 151,264 on odometer, 4L with 6 speed manual (NSG370)

    Problem: My daily is in the shop and I was driving the jeep to work today when it went into what can only be described as limp mode. I was less than 3 miles from the house when it stopped accelerating, downshifting did not help. I pulled off to the side of the road, turned on the hazards, and checked for codes - there were none and CEL was not illuminated. There was the strong scent of exhaust in the cabin.

    I limped back home, I do not believe mph exceeded 20, RPM rarely (if ever) exceeded 2000. I was trying to watch both the tachometer and speedometer but with traffic whizzing by me at 75+ mph, my attention was on the road and not getting hit!

    Backstory (as complete and detailed as possible):

    Starting last June, I would get an intermittent CEL. It was P0421, Warm up catalyst efficiency below threshold. I got the code several times, sometimes it would clear on its own, sometimes I'd clear it with my bluetooth OBDII reader/Torque (lite) app on my phone.

    At the end of January, the jeep developed an annoying squeal. I was on my way to a wrenching party and the noise went away once the engine was up to normal operating temp. I let it cool back down then had everyone at the wrenching party listen and help me find the issue.

    The sound was not a belt or pulley squeal, it had a much different sound and I had also installed new pulleys and serpentine belt when I replaced the radiator. All (or nearly all) parts were replaced between the radiator and thermostat. It turned out that the sound was coming from the OPDA.

    The jeep was driven very minimally (2-4 times a month) between that wrenching party and last weekend. I did run Log Corral on March 24th and on the way to airdown, the jeep was not holding speed going uphill, even in 4th and 5th gear.

    OPDA was changed out this weekend, I followed the directions found on YouTube exactly - plastic pin was pulled from new unit, motor was cranked by hand until the pin could be inserted in unit currently installed. Once the old unit was pulled, the pin was placed back in the new unit and it was installed. I also reused the old sensor as advice found on forum posts re: OPDA mentioned the Crown unit was a better design than OEM but the OEM sensor worked better than the Crown. After install, the jeep was run until up to operating temp then I drove it for 5-10 min. I drove approx 5 miles and was able to get it up to 65. When shifting between (I believe) 3rd and 4th, I felt some hesitation but was able to get up to 6th and drive at 65 for approx 1 mile before turning around and heading home. On my way home, I did not notice the hesitation and was again able to drive 65 for approx 1 mile.

    Solution: Here is where I need your help!
    Timing off? Catalytic converter/s need to be replaced?

    I don't want to just throw parts at it nor do I want to have it towed all over the valley chasing down theories! Has anyone seen or run into this before? I know there's a wealth of knowledge here that can help me pinpoint what's causing the problem.

    Sent from my SM-G950U using Tapatalk

  2. #2

    Re: Need Help Diagnosing Problem

    or take it to a shop, pay them to figure it out, you would be dollars ahead

  3. #3
    Join Date
    Feb 2013
    Location
    Peoria, Arizona, United States
    Posts
    514

    Re: Need Help Diagnosing Problem

    I just went through my own situation in the last week. I wont tell you what mine was because I dont think it pertains to your situation.

    However, this is my second Jeep and I have learned the hard way many times that it is very simple to just start throwing money at them. From sensors to gaskets, etc.. You can waste a lot of energy and money on things that make no difference even though to a good machanic the theory was mechanically sound. Then you find out it wasnt the problem after turning wrenches for the entire weekend. Now your left with out a Jeep, few hundred $$, out of beer, and your have ran out of wrenches and cuss words to throw.

    My best advice is to find a good shop that will diagnose. Dont let the shop scare you and dont let them feed you the "crap". Tell them exactly whats happening and have them look it over. Before you give them the key get a confirmation from them on pricing to look it over and make sure they arent going to charge you for some guy to just stare at the motor.

    After throwing money and sensors at mine last week thinking I new the problem I drew the line and had a mechanic buddy look at it who had been in the industry for 30+ years. It stumped him after a day or so and I towed it to a shop with bigger and better machine. All in all my diag cost me $90 and I had a clear cut answer which gave me more time to find a new solution.

    This is purely my $.02 but want to help support what Wiley was stating.

  4. #4
    Join Date
    Feb 2013
    Location
    Peoria, Arizona, United States
    Posts
    514

    Re: Need Help Diagnosing Problem

    On a side note:

    If it it maybe a cat problem, or an exhaust leak issue (hole somewhere not seen?) maybe try a can of seafoam through the intake and see where smoke comes out? The seafoam will also help clean the cat as the blows through as well. Just a thought.

  5. #5
    Join Date
    Jan 2014
    Location
    Maricopa
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    Re: Need Help Diagnosing Problem

    I live in Maricopa, there are not many options here. I figured I'd ask if anyone else has experienced what's going on before calling AAA and having it towed somewhere.

    It's not critical that this be fixed NOW, it's not my daily. If it were critical, I would have been on the phone making arrangements, not a forum post. The timing was not ideal, with the daily being in the shop . At least I have PTO so today wasn't a total loss!

    I found a local mobile mechanic I might try. His reviews are all excellent, even those not recommended by Yelp. Called to see if I could make an appointment and he's on vacation this week. Another option is to have it towed to the same shop where the daily is getting work done.

    If anyone has a trusted mechanic in the Maricopa, SW Chandler, S Tempe area, I'm open to recommendations.


    Sent from my SM-G950U using Tapatalk

  6. #6
    Join Date
    Jan 2012
    Location
    Buckeye, Az.
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    7,956

    Re: Need Help Diagnosing Problem

    I may have a good cat you can have, should you decide to change it. I misdiagnosed mine, thought it was the cat and it was severe leaks in the exhaust manifold. I'll look tonight.
    Non-College Educated Working Class White Deplorable....

  7. #7
    Join Date
    Jan 2014
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    Maricopa
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    Re: Need Help Diagnosing Problem

    Quote Originally Posted by OTR-93YJ View Post
    I may have a good cat you can have, should you decide to change it. I misdiagnosed mine, thought it was the cat and it was severe leaks in the exhaust manifold. I'll look tonight.
    Thank you! I'll update once I'm able to have the jeep diagnosed by a professional. I will keep watching for any new posts though.

    I may wait at least a week or 2, this month has been VERY costly!

    Sent from my SM-G950U using Tapatalk

  8. #8
    Join Date
    Mar 2015
    Location
    Dewey
    Posts
    71

    Re: Need Help Diagnosing Problem

    I have had a couple jeeps with really clogged cat the exhaust manifold/header would glow red hot at the collector,if your cat is plugged that bad to restrict that much power check it at idle with some rpms flowing through it check the temperatures at the collector and on down the exhaust past the cat might help your diagnoses


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  9. #9
    Join Date
    Nov 2010
    Location
    Ahwatukee
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    6,056

    Re: Need Help Diagnosing Problem

    My Jeep is at Interstate Auto right now getting a CEL taken care of. They have always been good to me and are in S Tempe. I should have mine back soon if you need a DD, just let me know and its yours. You have my cell #.

  10. #10
    Join Date
    Aug 2006
    Location
    Gilbert
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    2,314

    Re: Need Help Diagnosing Problem

    Your symptoms definitely line up with a bad cat. I'd say replacing that is a safe money bet.

  11. #11
    Join Date
    Jan 2012
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    Buckeye, Az.
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    Re: Need Help Diagnosing Problem

    I'm 99% sure I have the cat. didn't get a chance to look for it last night, but will tonight.
    Non-College Educated Working Class White Deplorable....

  12. #12
    Join Date
    Jan 2007
    Location
    East Mesa
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    2,046

    Re: Need Help Diagnosing Problem

    05-06 LJ's have 3 cats. I think the 04's do as well but be sure to check that. There are two that are part of the lower exhaust manifold assembly right up next to the engine. The third is before the muffler. You should be able to pull the third cat out without an CEL's, I don't remember an 02 sensor back there. Would be fine for a quick check to just unbolt there and go for a drive.

    When my OPDA went out on my 06, It ran find till about 3K RPM and then fell on its face. It did throw a code, but took a few times above 3K to register. I wouldn't count that out yet. I had to have the sensor adjusted after replacement even though I followed all the directions. Basically, I didn't get it back to where it was originally and the computer was not getting the correct signal.
    It's like an LJ... only bigger.

  13. #13
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    Maricopa
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    Re: Need Help Diagnosing Problem

    Quote Originally Posted by Estrada View Post
    My Jeep is at Interstate Auto right now getting a CEL taken care of. They have always been good to me and are in S Tempe. I should have mine back soon if you need a DD, just let me know and its yours. You have my cell #.
    Thank you for your generous offer! I had the daily back from the shop so I'm good, just jeep-less!

    Sent from my SM-G950U using Tapatalk

  14. #14
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    Nov 2010
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    Re: Need Help Diagnosing Problem

    Quote Originally Posted by greyst View Post
    Thank you for your generous offer! I had the daily back from the shop so I'm good, just jeep-less!

    Sent from my SM-G950U using Tapatalk
    Good to hear. LMK if you need any help. Cats in newer TJs suck. They are expensive!

  15. #15
    Join Date
    Dec 2003
    Location
    North Phoenix
    Posts
    8,409

    Re: Need Help Diagnosing Problem

    My vote is clogged cat.
    Loosen bolts at cat input, creating a leak and eliminating back pressure. If cat was clogged, it should run better. This is for diagnosis only. You would probably get O2 sensor code doing this.
    Quote Originally Posted by amber.hodge View Post
    Steve is so innocent. Its really cute, actually. Ah to be a kid again....
    "anyone who says they know everything about anything is either a fool or a liar"

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