NAXJA Forums -::- North American XJ Association  

Go Back   NAXJA Forums -::- North American XJ Association > NAXJA Unibody Jeep Technical Forums > Jeep Cherokee XJ (1984 - 2001) > OEM Tech Discussion
HOME Member FAQ Sponsor Info Rules Bylaws E-Mail

OEM Tech Discussion Forum for OEM (Original Equipment) or stock XJs and MJs.

Reply
 
Thread Tools Display Modes
  #1  
Old December 18th, 2019, 08:52
gearwhine gearwhine is offline
NAXJA Member
 
Join Date: Jun 2002
Location: Denver, CO
Posts: 974
Help with diagnosing rattling noise under light load

I'll try to be as complete as possible. I feel it's all required to provide some input

I bought a 1996 Jeep Cherokee I-6 AW4 NP231 with ~135,000 a few months back.

Starting off....everything runs great, no stuttering, no rumbling, no shifting issues. It's all tight and doesn't feel under-powered. No OBDII codes are present.

I changed the oil to NAPA Synthetic 10w-30 with a NAPA/Wix Platinum Filter. I changed the air filter with it.

A week or two later, I noticed a slight rattling sound. I'm not necessarily saying it started at that point...I'm just saying I noticed it. It happens under extremely light load and up when moving or not moving. I can re-created it with my e-brake on and a press on the accelerator. It's pretty much unrecognizable at idle. It does become prevalent (to me) when I lightly place my foot on the accelerator....so light that the RPMs don't even go up. I feel that detail might be important...maybe?

I first checked all the basics...fluid levels etc. Recognized I forgot to connect my air intake back in the throttle body, so I essentially ran ~200 miles bypassing the air filter. Whoops...likely a non-issue from my diagnosing at this point.

I then looked at the shop information from the previous owner, and it was always maintained with 5w-30 Amsoil synthetic for the 5 years of back data I received.

I have now driven it around 5-600 miles since that time. The sound has not appeared to get worse. It's hard to hear if I have HVAC on medium to high....but my ears are tuned so perfectly to hear the rattling now.

My current diagnosing-

I have gotten nearly everywhere with a stethoscope (stethoscope diagnosing is new to me, so I don't know what sounds are normal). It does sound like the bottom end has a more metallic sound at idle. Not ticking, not thumping...just sounds like the crank bearings are dry or something similar. I take it that's a normal sound...but throwing that out there. I'm likely going to change back to 5w-30 this weekend to see if that sound changes.

Valve cover sounds great even when applying gas with my hand at the throttle body lever. Head sounds smooth.

I have have tried 85, 87, and 91 octane fuels...no change....so very likely not pinging.

I am not seeing any issues with exhaust....but that doesn't mean it's not a leak or a metal contact I'm missing.

I have placed the transmission into neutral with no accelerator during cruise speed. The rattle is still there, but it's not as loud.

I have used sound deadening tape at many interior plastic contact points...my interior is pretty damn noiseless.

Any other thoughts on potential causes? I'm beginning to think it's a non-issue.

Thanks!

-Nick
Reply With Quote
  #2  
Old December 18th, 2019, 09:56
MickeyS MickeyS is offline
NAXJA Forum User
 
Join Date: Apr 2018
Location: Pasadena
Posts: 103
Re: Help with diagnosing rattling noise under light load

sure it's not exhaust? maybe drop by an exhaust/muffler shop just to be sure. they can look for any metal on metal contact points you may have missed? had this issue with rattle at the gas tank skid plate that I couldn't see from the ground with my untrained eye.
Reply With Quote
  #3  
Old December 18th, 2019, 10:13
asymptonic asymptonic is offline
NAXJA Member
 
Join Date: Jul 2012
Location: Austin, Texas
Posts: 263
Re: Help with diagnosing rattling noise under light load

Could be lifter tick, which is sensitive to oil thickness.
__________________
1998 4.0 I6, AX15, NP231
Reply With Quote
  #4  
Old December 18th, 2019, 13:47
emx721 emx721 is offline
NAXJA Forum User
 
Join Date: Jan 2017
Location: wisconsin
Posts: 42
Re: Help with diagnosing rattling noise under light load

See if it's coming from the purge solenoid (like mine does for years now)
Reply With Quote
  #5  
Old December 18th, 2019, 20:24
Runnin'OnEmpty's Avatar
Runnin'OnEmpty Runnin'OnEmpty is offline
NAXJA Forum User
 
Join Date: Apr 2003
Location: Southeast USA
Posts: 1,109
Re: Help with diagnosing rattling noise under light load

Quote:
Originally Posted by gearwhine View Post
...........
A week or two later, I noticed a slight rattling sound. I'm not necessarily saying it started at that point...I'm just saying I noticed it. It happens under extremely light load and up when moving or not moving. I can re-created it with my e-brake on and a press on the accelerator. It's pretty much unrecognizable at idle. It does become prevalent (to me) when I lightly place my foot on the accelerator....so light that the RPMs don't even go up. I feel that detail might be important...maybe?.............
My 96 has the same rattle. After checking the torque converter bolts, I've just about isolated it to the catalytic converter. It's louder on the passenger side and can be heard when laying on the ground next to the cat.

There was a recall on the cats for the 96 model year. It seems the honeycomb material was breaking loose from the case and rattling around on the inside...
Reply With Quote
  #6  
Old December 18th, 2019, 22:12
MickeyS MickeyS is offline
NAXJA Forum User
 
Join Date: Apr 2018
Location: Pasadena
Posts: 103
Re: Help with diagnosing rattling noise under light load

Quote:
Originally Posted by Runnin'OnEmpty View Post
My 96 has the same rattle. After checking the torque converter bolts, I've just about isolated it to the catalytic converter. It's louder on the passenger side and can be heard when laying on the ground next to the cat.

There was a recall on the cats for the 96 model year. It seems the honeycomb material was breaking loose from the case and rattling around on the inside...
can confirm this is also true, and when mine finally bit the dust it failed smog. I was worried there was some other issue causing the cat to fail like there usually is but fuel trims are good and as soon as the cat was replaced it passed ca smog easily.

I'm betting it's exhaust related
Reply With Quote
  #7  
Old December 19th, 2019, 06:18
gearwhine gearwhine is offline
NAXJA Member
 
Join Date: Jun 2002
Location: Denver, CO
Posts: 974
Re: Help with diagnosing rattling noise under light load

Thanks everyone.

To answer MickeyS's original question....definitely not sure about anything!

With that...I'll scour the entire exhaust system thoroughly before anything else. I'll bring it to a shop if I find nothing. It did pass Denver air emissions and inspection when I bought it though...so it's likely not entirely toast even if the sound is from the cat.

I do recall now that my previous 96 had a cat issue. When I pulled it off, it basically had a clump rolling around in it. That happened with only around 50k miles on it.

If I find nothing, I'll go back to 5W-30 and see if anything changes with lifters or bottom end noises.

I'll then check purge solenoid. Appreciate the input so far!

-Nick
Reply With Quote
  #8  
Old December 19th, 2019, 10:41
Anak's Avatar
Anak Anak is offline
Stranger
 
Join Date: Sep 2013
Location: In a strange land
Posts: 3,537
Re: Help with diagnosing rattling noise under light load

Another possible source would the timing chain. There is a factory dampener inside the timing cover. It was originally a piece of rubber. By now it is hard as plastic. Perhaps under the right conditions something is going on between that dampener, the chain and the cover.

IIRC that dampener is on the passenger side of the timing cover, meaning it is behind the AC/Alternator brackets where they mount to the cover. IOW, it will be a PITA to try to get to that area with a stethoscope/wooden rod.
__________________
Project "Scope Creep": 1996 4wd 4.0L, AX15
....

Baby it's cold outside.
Reply With Quote
  #9  
Old December 19th, 2019, 11:39
emx721 emx721 is offline
NAXJA Forum User
 
Join Date: Jan 2017
Location: wisconsin
Posts: 42
Re: Help with diagnosing rattling noise under light load

You can just disconnect the purge valve solenoid for a few minutes and drive around. If you don't hear the rattle you know the solenoid is the cause.
Reply With Quote
  #10  
Old June 22nd, 2020, 20:53
Runnin'OnEmpty's Avatar
Runnin'OnEmpty Runnin'OnEmpty is offline
NAXJA Forum User
 
Join Date: Apr 2003
Location: Southeast USA
Posts: 1,109
Re: Help with diagnosing rattling noise under light load

I finally got around to replacing my catalytic converter, because of the rattle.
Once removed, it's obvious where the noise is coming from. The honeycomb
material had broken loose from the housing and was rattling back and forth
inside the converter shell.

Because of the U-clamp Jeep used to connect the cat to the intermediate pipe,
it's necessary to cut a slit in the pipe in order to slide it over the bulge created
by the U-clamp. I used a cut-off wheel but it still took a long time cutting through
the stainless steel of the cat pipe...
Reply With Quote
  #11  
Old June 26th, 2020, 18:57
gearwhine gearwhine is offline
NAXJA Member
 
Join Date: Jun 2002
Location: Denver, CO
Posts: 974
Re: Help with diagnosing rattling noise under light load

Hey all,

Just following up since a new post has come in...and it seems Runnin' has fixed their problem, which is great!

No repair or diagnosis yet on mine. I did just recognize a slight head gasket leak (visible off the front), so that's going to be what I attack next. I'll be able to check the timing chain then. I'll absolutely post as things come to fruition.
Reply With Quote
  #12  
Old June 26th, 2020, 22:43
Agreen Agreen is offline
NAXJA Forum User
 
Join Date: Nov 2016
Location: Charleston
Posts: 41
Re: Help with diagnosing rattling noise under light load

I had a rattle on light acceleration that drove me nuts. You can read the thread below, but I'll save you the time. It was the engine mounts. Your mileage may vary.

https://www.naxja.org/forum/showthread.php?t=1134969
Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Diagnosing a noise SolarBell Colorado Chapter 53 March 12th, 2013 15:34
Strange Noise and Need Help Diagnosing 98NWCherokee OEM Tech Discussion 7 July 29th, 2012 14:53
Need help diagnosing noise XJSlater OEM Tech Discussion 3 August 17th, 2008 22:42
Need some help diagnosing a noise 01_XJ OEM Tech Discussion 17 March 13th, 2007 08:25
Rattling noise when under load. SDxjsport OEM Tech Discussion 5 July 11th, 2005 20:24


All times are GMT -7. The time now is 04:44.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
NAXJA and NAXJA logo's Copyright NAXJA. All content/images Copyright NAXJA 1999-2014