Intermittent Fast Fluttering Sound on Acceleration

[RH2001TJ]

Hi Fellow Jeepers, new to posting but have found many answers from the collective genius here. I have a 2001 TJ Sport, 4.0L, Automatic (I know, but she don't stall in low range jaunts). I am experiencing an intermittent issue that I hope someone out there will have some ideas on what it may be: When accelerating under load between 2,000-2,500 rpm I sometimes get a loud fluttering noise. I have read some other posts on fluttering noises, but they always seem to veer off course and talk about blower switches and such. My issue is just fluttering/v-r-r-r-r-ing on acceleration and sometimes on kick-down while passing. Also, after such an event she seems to idle rough until the next run cycle. Some type of intake or exhaust thing? New coil pack, new O2 sensors (NTK), dreaded K&N CAI. The first time this happened was just after transmission rebuild, but I think that was coincidental. Not sure if charcoal canister (?) or vacuum (?) may be suspect. Idles perfect and runs great, other than the occasional gremlin growl... Any ideas?

 

[D M]

If I were to take a guess, I have heard that some cold air intakes make a little noise, such as k&n, bbk, etc. They make a deep vacuum like sound under acceleration. Maybe it could be a placebo now that your just noticing it? Im not quite sure. Does it idle well and does it accelerate smooth?

 

[RH2001TJ]

If I were to take a guess, I have heard that some cold air intakes make a little noise, such as k&n, bbk, etc. They make a deep vacuum like sound under acceleration. Maybe it could be a placebo now that your just noticing it? Im not quite sure. Does it idle well and does it accelerate smooth?

Hi Dylan. She runs great. You are right, sounds like a 737-100 on start up with the choke closed... but otherwise idles perfect and drives fine. This issue only happens occasionally, and only under acceleration load. I still have my stock airbox and will try that change to see if it could be the CIA. Hope not as she certainly has more power (perceived) with the CIA...

 

[D M]

Hi Dylan. She runs great. You are right, sounds like a 737-100 on start up with the choke closed... but otherwise idles perfect and drives fine. This issue only happens occasionally, and only under acceleration load. I still have my stock airbox and will try that change to see if it could be the CIA. Hope not as she certainly has more power (perceived) with the CIA...

As many others will tell you, cold air intake kits maybe add 0-3 hp which really isnt noticable. Most CAI kits just let in more dirt and are actually worse at filtering in cold air because its still coming under the hood.

 

[Chris]

Not even the slightest clue with this one.

I'm not sure what the noise would have to do with a rough idle either. It's not throwing any check engine lights?

 

[RH2001TJ]

As many others will tell you, cold air intake kits maybe add 0-3 hp which really isnt noticable. Most CAI kits just let in more dirt and are actually worse at filtering in cold air because its still coming under the hood.

Hi Dylan, agreed. Will be putting the stock box back on. Thanks for your replies.

 

[RH2001TJ]

Not even the slightest clue with this one.

I'm not sure what the noise would have to do with a rough idle either. It's not throwing any check engine lights?

Hi Chris, yep it’s a mystery. No codes, no real drive problems except when it flaps/vrrrrs, significant power loss. Restart and she is a happy Jeep again...

 

[RH2001TJ]

Hi Chris, yep it’s a mystery. No codes, no real drive problems except when it flaps/vrrrrs, significant power loss. Restart and she is a happy Jeep again...

179k on the clock and haven’t done much replacing under hood yet except coils and O2s. Of course the K&N...

 

[Chris]

I'd personally keep driving it. It sounds like a check engine light will come on soon, in which case that will point you in the right direction. Because right now, this is a hard one to diagnose.

 

[Not_Invented_Here_]

Can you elaborate on fluttering or flapping sound a bit?

If you were ever a kid riding a bike and you stuck a playing card or something between your wheel spokes to get that rapid ticking sound, sometimes I get a light version of that when accelerating and I'm wondering if that's what you mean ha.

Really just curious more than anything, don't know that it's indicative of a problem ha. I pulled all my carpets for the summer and am quickly becoming acquainted with the many sounds I had previously tuned out or hadn't noticed when carpet was still in.

 

[RH2001TJ]

Can you elaborate on fluttering or flapping sound a bit?

If you were ever a kid riding a bike and you stuck a playing card or something between your wheel spokes to get that rapid ticking sound, sometimes I get a light version of that when accelerating and I'm wondering if that's what you mean ha.

Really just curious more than anything, don't know that it's indicative of a problem ha. I pulled all my carpets for the summer and am quickly becoming acquainted with the many sounds I had previously tuned out or hadn't noticed when carpet was still in.

Good sound effect description! My mystery noise is like a VRRRRRRRRRing sound, with a loss of power. Only does it occasionally and once it’s doing it I can repeat with peddle mashing. Next run cycle, no issue...

 

[RH2001TJ]

I'd personally keep driving it. It sounds like a check engine light will come on soon, in which case that will point you in the right direction. Because right now, this is a hard one to diagnose.

Hi Chris, agreed. Will put the stock air box back on this weekend and see if that resolves things. Otherwise wait to see if she throws a CEL. Thanks!

 

[Chris]

Hi Chris, agreed. Will put the stock air box back on this weekend and see if that resolves things. Otherwise wait to see if she throws a CEL. Thanks!

Sounds like a solid plan. Let us know if you uncover anything new

 

[RH2001TJ]

Hi Fellow enthusiasts, thanks for all of your suggestions. Here’s what I’ve found so far;
Mystery noise solved- Bendix gear return spring failure in starter allowing engagement and spinning the motor, new starter and no more noise!
Additional issue was bad tranny repair shop put the inspection cover on with wrong bolts and not aligned with the tabs, contacting flex plate on acceleration. Dumb-bubs used wrong bolts everywhere, had to have another shop resolve for $400, but now all good.
Finally got some CEL codes, P0300, 0301, etc. New crank and cam sensors resolved most, but still had the random P0300 and flashing CEL on deceleration from 65 mph at around 50-52 mph. New plugs got P0300, 0303, and 0306 and limp home mode. Compression test found cylinder 3 at 60psi... Valve job scheduled. Shop owner who only works on our beloved Jeeps had a lot to say about cylinders 3 and 6 having valve issues.
I think our TJ PCM’s set the P0300 code as a default when they can’t really figure out what is wrong. Running home to momma in confusion. Anyway, will post results after valve job and hoping all will be well under the hood. Take care and Jeep On!

 

[Ledfoot Lou]

Hi Fellow enthusiasts, thanks for all of your suggestions. Here’s what I’ve found so far;
Mystery noise solved- Bendix gear return spring failure in starter allowing engagement and spinning the motor, new starter and no more noise!
Additional issue was bad tranny repair shop put the inspection cover on with wrong bolts and not aligned with the tabs, contacting flex plate on acceleration. Dumb-bubs used wrong bolts everywhere, had to have another shop resolve for $400, but now all good.
Finally got some CEL codes, P0300, 0301, etc. New crank and cam sensors resolved most, but still had the random P0300 and flashing CEL on deceleration from 65 mph at around 50-52 mph. New plugs got P0300, 0303, and 0306 and limp home mode. Compression test found cylinder 3 at 60psi... Valve job scheduled. Shop owner who only works on our beloved Jeeps had a lot to say about cylinders 3 and 6 having valve issues.
I think our TJ PCM’s set the P0300 code as a default when they can’t really figure out what is wrong. Running home to momma in confusion. Anyway, will post results after valve job and hoping all will be well under the hood. Take care and Jeep On!

Thank you soooo much for reporting back when you found the issue. I think i might have a similar issue and can't wait to check it out.

 

[RH2001TJ]

Hey there Jeep-nuts, flashing CEL with P0300, etc. codes solved!
Had the valve job done, found #3 and #6 exhaust valves burnt, lots of carbon build-up on the head surfaces. My new go-to guys at BIKINI OFFROAD here in San Antonio did everything but an exorcism to find the problem: Overdrive lock-up solenoid harness wires bare and shorting, causing the PCM to not see the signal to change fuel mapping on deceleration from highway speed, which overloads the fuel ratio and causes the misfires. This is also the probable cause of the carbon build up.
Just another issue from the crap tranny shop dumbos... I do recall they advised some bare wires that they “fixed”, and that lead Master Tech Mike to look there. The “fix” the dumbos did was to just wrap some tape around the bare wires, not individually mind you!!!
Long story short, my beast is back, no more CEL, and she runs smooth and strong.
Thanks again to all for your thoughts and advice. I hope my experience may help one of you some day. Jeep On!

 

[RH2001TJ]

Thank you soooo much for reporting back when you found the issue. I think i might have a similar issue and can't wait to check it out.

Good luck Ledfoot, my new Master Tech, Mike, has advised many trouble spots on our aging wire lumes; back of the valve cover where it all comes together to go to PCM, many injector and other sensor issues. A lot of our Jeep’s are missing the plastic lume support tray that is supposed to be there keeping it off the back of the engine. Left side branch that goes to cam shaft sensor and alternator, timing and misfire codes, plus a bunch of power related stuff. Anyway, a close inspection of the wiring may yield some resolution to those mystery issues. Jeep on!

 

[06TJX]

Hi Fellow enthusiasts, thanks for all of your suggestions. Here’s what I’ve found so far;
Mystery noise solved- Bendix gear return spring failure in starter allowing engagement and spinning the motor, new starter and no more noise!
Additional issue was bad tranny repair shop put the inspection cover on with wrong bolts and not aligned with the tabs, contacting flex plate on acceleration. Dumb-bubs used wrong bolts everywhere, had to have another shop resolve for $400, but now all good.
Finally got some CEL codes, P0300, 0301, etc. New crank and cam sensors resolved most, but still had the random P0300 and flashing CEL on deceleration from 65 mph at around 50-52 mph. New plugs got P0300, 0303, and 0306 and limp home mode. Compression test found cylinder 3 at 60psi... Valve job scheduled. Shop owner who only works on our beloved Jeeps had a lot to say about cylinders 3 and 6 having valve issues.
I think our TJ PCM’s set the P0300 code as a default when they can’t really figure out what is wrong. Running home to momma in confusion. Anyway, will post results after valve job and hoping all will be well under the hood. Take care and Jeep On!

I have the same fluttering noise during low rpm, minimal throttle around 30-40mph... my wrangler is showroom stock with 36k miles. would love to resolve the issue. Confirming, replacing the starter fixed it??

 

[06TJX]

Good sound effect description! My mystery noise is like a VRRRRRRRRRing sound, with a loss of power. Only does it occasionally and once it’s doing it I can repeat with peddle mashing. Next run cycle, no issue...

did it sound like this?? my 06 TJ with a 4.0 auto. makes this noise intermittently with 25-30mph lite acceleration.