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  #16  
Old August 12th, 2017, 20:52
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alexgalexg alexgalexg is offline
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Re: Bad Transmission?

My other Xj is a 99 and has done 300k downshifting at the same speeds and conditions this 98 does but didnt buck. I still think its worth my time to investigate but as I said it has always shifted this way and so has my 99 with no bucking. But yes it very much feels like the transmission is what is bucking not the engine. I can feel it coming from that area and not the engine not to mention the engine always runs smooth.
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  #17  
Old August 12th, 2017, 22:39
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Re: Bad Transmission?

Quote:
Originally Posted by Ecomike View Post
If the TC is not locked, the TC fluid slippage should not allow it it to buck, at all.

There is a difference between an engine miss-shake, and an entire drive train bucking. It feels very different.

If it is in gear with a clutch engaged or the AW4 TC is locked, yes an engine miss can cause bucking.
I was merely giving an option based on my experience...you wouldn't believe how many customers use the term "buck" to describe a misfire.

This is the problem with Internet diagnosis...everyone describes symptoms differently.
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  #18  
Old August 12th, 2017, 22:47
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Re: Bad Transmission?

Have you considered making a video of what's happening? Post it on YouTube and we could check it out?

Also, if it downshifts similarly to your other jeep...then it seems unlikely that downshifting is an issue.

Am I correct in assuming you do not have a check engine light on? Do you have access to a scantool that can check misfire counters? That would be an easy way to rule out one possibility.
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88 MJ on 40's. 98 XJ on 35's. 98 Dodge, 52psi of boost. 94 Miata LS4. 70 Buick GS455. 01 Harley, been to 46 states. 05 KTM, 576cc. 06 Husky, girls need bikes too. 2011 R6, girls need sport bikes too. 99 Toyota Avalon, daily. 97 Miata, girls apparently need miatas too.
And everything fits in the garage!
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  #19  
Old August 12th, 2017, 23:11
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Re: Bad Transmission?

I can borrow a scan tool hopefully tomorrow to check it out. I can make a video for you all. In fact I recently started making repair videos for Jeeps in my spare time so I can just upload it to that channel. It is likely not going to show on video when it is "bucking" though because the engine runs smooth and as it should the entire time. But I can show you the speed and rpm so it may help.

Likely unrelated but favor needed
Someone noted that the brand new o2 upstream could be bad despite no check engine light and the fact that it is only a matter of months old. I really doubt it is bad because it seems like a quality sensor however I only replaced it because the wire had gotten torn off the sensor after off roading. Driving with a non working o2 sensor feels more like a hesitation or a car with a small carb issue feels like but only on occasion. It felt nothing like what I am talking about here. I only bring it up because the plastic connector was broken. I was very careful to make sure the o2 four pins got installed the correct way when I put it all together. But if anyone has detailed pics of the connector on a 97-99 xj for me to be sure just email me alexbg123@gmail.com

Last edited by alexgalexg; August 12th, 2017 at 23:19.
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  #20  
Old August 13th, 2017, 04:59
Jeep Driver Jeep Driver is offline
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Re: Bad Transmission?

Quote:
Originally Posted by alexgalexg View Post
I can borrow a scan tool hopefully tomorrow to check it out. I can make a video for you all. In fact I recently started making repair videos for Jeeps in my spare time so I can just upload it to that channel. It is likely not going to show on video when it is "bucking" though because the engine runs smooth and as it should the entire time. But I can show you the speed and rpm so it may help.

Likely unrelated but favor needed
Someone noted that the brand new o2 upstream could be bad despite no check engine light and the fact that it is only a matter of months old. I really doubt it is bad because it seems like a quality sensor however I only replaced it because the wire had gotten torn off the sensor after off roading. Driving with a non working o2 sensor feels more like a hesitation or a car with a small carb issue feels like but only on occasion. It felt nothing like what I am talking about here. I only bring it up because the plastic connector was broken. I was very careful to make sure the o2 four pins got installed the correct way when I put it all together. But if anyone has detailed pics of the connector on a 97-99 xj for me to be sure just email me alexbg123@gmail.com
Now I'm even more convinced it's your O2

NTK only.
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  #21  
Old August 13th, 2017, 10:12
macgyver_7_6 macgyver_7_6 is offline
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Re: Bad Transmission?

I know you have said it doesn't feel like a misfire...but I never rule out any possibilities until the problem is fixed. Have you ever broken any tabs on the injectors? Long shot, but maybe one is causing an issue under load. And, how do you know your fuel pump is operating correctly under load? I had an 86 XJ that ran fine up to a certain rpm range, then puky at higher rpms.

I'm pro-maintenance...so if your fluid isn't red....I would change filter & fluid.
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  #22  
Old August 13th, 2017, 13:26
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Re: Bad Transmission?

Fuel pump is new, injector tabs are all in good shape, o rings on injectors are new both sides of injectors, fuel pump is brand new and designed for high performance, engine does not run poorly at any rpm. Trans fluid is on my list to do after diff fluid. I just have to find the time because I work two jobs and college starts soon.
I am not disagreeing with you about the misfire, I am definitely taking it all into account in order to trouble shoot this
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  #23  
Old August 13th, 2017, 16:23
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Re: Bad Transmission?

Ok update I checked trans fluid levels (the proper way) and still came back at good levels. However on my ride home today I was diving up an incline at 45 maybe 47 and got a big jolt from the transmission. I was trying to record but it is very hard to do in traffic so I didnt catch it
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  #24  
Old August 13th, 2017, 21:53
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Ecomike Ecomike is offline
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Re: Bad Transmission?

Just to be clear, under a load, like climbing a grade, with the TC locked, all it takes is enough misfires to make them buck. But if the TC is unlocked a misfire should not make it buck, IMHO. But with a TC not unlocking, with more load than the engine can handle (at low rpms), that can cause misfires that then cause it to buck. I hope that clarifies what I was trying to say.

Quote:
Originally Posted by JohnX View Post
Have you considered making a video of what's happening? Post it on YouTube and we could check it out?

Also, if it downshifts similarly to your other jeep...then it seems unlikely that downshifting is an issue.

Am I correct in assuming you do not have a check engine light on? Do you have access to a scantool that can check misfire counters? That would be an easy way to rule out one possibility.
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  #25  
Old August 13th, 2017, 22:10
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Re: Bad Transmission?

Quote:
Originally Posted by Ecomike View Post
Just to be clear, under a load, like climbing a grade, with the TC locked, all it takes is enough misfires to make them buck. But if the TC is unlocked a misfire should not make it buck, IMHO. But with a TC not unlocking, with more load than the engine can handle (at low rpms), that can cause misfires that then cause it to buck. I hope that clarifies what I was trying to say.
Respectfully , I'm not too sure what you mean. I don't think we're really in disagreement here, just saying things differently.

Even on older vehicles, without lockup converters, it's pretty easy to feel a mis, and a lot of people describe it as bucking.
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88 MJ on 40's. 98 XJ on 35's. 98 Dodge, 52psi of boost. 94 Miata LS4. 70 Buick GS455. 01 Harley, been to 46 states. 05 KTM, 576cc. 06 Husky, girls need bikes too. 2011 R6, girls need sport bikes too. 99 Toyota Avalon, daily. 97 Miata, girls apparently need miatas too.
And everything fits in the garage!
Quote:
Originally Posted by mako my day View Post
Johnx is #1
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  #26  
Old August 14th, 2017, 13:54
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Re: Bad Transmission?

It is a miss. I got home today and before I shut off the vehicle I could feel the miss. I got out of the vehicle with it still running and you could clearly hear the miss. I opened the hood to see what was going on, touched one lead and got shocked... so tomorrow I am going to buy new leads. Not sure how one year old leads are already causing problems but oh well. If that doesn't fix it I will look into o2 sensor wiring, fuel pump wiring and fuel line leaks
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  #27  
Old August 14th, 2017, 14:21
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Re: Bad Transmission?

Since the miss is now occurring even at idle I was able to record it
https://youtu.be/CjR1shGqK88
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  #28  
Old August 14th, 2017, 17:09
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Re: Bad Transmission?

Another sure fire way to check plug wires especially.....mix up a solution of salt water in a spray bottle. Then mist it onto the wires, a leaking wire will be very obvious...and do it at night without a flashlight, you'll see the spark jump from the bad wire.
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88 MJ on 40's. 98 XJ on 35's. 98 Dodge, 52psi of boost. 94 Miata LS4. 70 Buick GS455. 01 Harley, been to 46 states. 05 KTM, 576cc. 06 Husky, girls need bikes too. 2011 R6, girls need sport bikes too. 99 Toyota Avalon, daily. 97 Miata, girls apparently need miatas too.
And everything fits in the garage!
Quote:
Originally Posted by mako my day View Post
Johnx is #1
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  #29  
Old August 14th, 2017, 18:44
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Re: Bad Transmission?

Haha I will keep that in mind. Never touching a lead while a vehicle is running again
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  #30  
Old August 14th, 2017, 19:46
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Re: Bad Transmission?

Quote:
Originally Posted by alexgalexg View Post
Haha I will keep that in mind. Never touching a lead while a vehicle is running again
its okay to do if you don't become the ground, just don't lean on the fender
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