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Vibration at idle and around 2000rpm under acceleration
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Author:  MACKJ [ Tue May 12, 2009 11:12 pm ]
Post subject:  Vibration at idle and around 2000rpm under acceleration
Guys I need some help with the possible cause(s) for this very annoying vibration…

A vibration and “drumming” noise in the cabin is apparent when in drive or reverse with the brake on, such as when at traffic lights. Pop the transmission into neutral or park and the vibration almost disappears. Note that my perception is that the vibration is coming from the drivers side (right) of the vehicle and comes up through the floor and into the dash to create the drumming sensation.
A similar vibration and harshness results as the engine passes through 1800 to 2200 rpm during acceleration. Take your foot off the go peddle and it is quiet as a mouse when coasting.
When the engine is cold the vibration is much less (for a diesel). This problem develops as the engine warms up and is particularly annoying/worrying after about 20 minutes driving in city traffic.
The vibration is made worse by driving in full time 4WD, that is, when more torque is applied to the front axles and engine. However selecting 4WD FT only affects the vibration whilst driving through the 1880 to 2200rpm range but has no affect on the (at) idle vibration intensity.
Loading the engine up by using the air con makes no change to the noise or vibration.
My EGR is blocked off and I religiously clean/check the MAP sensor. I haven’t really had to clean the MAP for about a year since blocking off the EGR.
When the vehicle was under warranty Jeep had replaced the engine mounts (twice) and gearbox mount, replaced the front pump in the trans (twice) and installed the Suncoast TC when the second trans pump was installed, No change after all this work. The vibration has actually worsened over the last six months or so.
I have had some fantastic support from Ranger1 offline with this problem but both he and I have run out of ideas. Thus the reason for pleading to the wider LOST community.
Possible root causes I have identified from discussions, experience and some reading on various other forums are;


1. Engine mounts (don’t think so as there have been two new sets)
2. Gearbox Mount (at least one replacement has had no affect)
3. Torque converter (don’t think so as Suncoast has had no affect)
4. Exhaust mounts (replaced rear set as they were a little sloppy)
5. Front prop shaft (don’t think so as I have removed it and no change to the 2WD vibration)
6. Front axle CV joints (boots all good and no discernable movement)
7. Rear prop shaft uni joints (replaced both a couple of months ago with greasable units. No change to the at idle vibrations)
8. CCV Valve (read about this somewhere but the Provent has a built in pressure vent…not sure on this one?)
9. Alternator Pulley (seems OK ,checked operation. Free wheels one direction and can feel the spring resistance in the other direction. Serpentine belt does not bounce at all)
10. Engine (Harmonic Balancer) pulley (this one is difficult to fault find as it is so bloody hard to get at)
11. Injectors (they were checked about two years ago to see if there was any excessive return flow, that is, leaking. All good)
12. Injector Timing (this is controlled by the ECU?)
13. Valve timing (?)
14. Transfer case (?)
15. Crank position sensor (?)
16. Power steering (?)

All comments greatly appreciated.
Author:  BlackLibertyCRD [ Wed May 13, 2009 9:15 am ]
Post subject: 
engine miss? you need to do a cylinder balance test to see if all is equal.
Author:  nursecosmo [ Wed May 13, 2009 1:34 pm ]
Post subject: 
If the problem has been worsening I would first check:
#1 Unbalanced/deformed tire(s)
#2 Bent wheel rim
#3 Recheck motor mounts for tightness
#4 Bent/unbalanced drive shaft
#5 Balance shaft(s) jump a tooth

If you still can't find the problem, you could just imagine that you have a Cummins 4BT under the hood. Image
Author:  ChesterCRD [ Wed May 13, 2009 2:59 pm ]
Post subject: 
MACKJ,

I have been chasing a problem similar to this for about a year now and haven't found it. I'm wondering how similar.

1. How noticeable is the sound outside the vehicle? Mine is really hard to hear unless you're inside.

2. Have you probed around the engine bay with a listening tool? I use a long pry bar with the handle against my ear to try to localize the noise better. I hear it best in the cross member just forward of the oil pan. I haven't been able to figure out what's causing it though.

Mine also comes and goes....some days it's louder than others. I took it in the dealer to have them look at it (out of warranty, but this has been frustrating me) and that particular day it didn't do it at all. Other days my wife (who notices nothing) actually asked me what it was...so I know it's not just me.
Author:  CRDMiller [ Wed May 13, 2009 4:01 pm ]
Post subject: 
MACKJ, Are you sure this is not normal? My engine Lugs when on the break and in drive or R . such as when at a stop light. This is especially loud when in 4wd, the front end transfers the lugging harmonic much more.

The noise while driving is not so normal, i would seriously look at getting the balance of your REAR drive shaft checked (including the slip yoke), OR pull the shaft and drive in 4 FT and see if it reproduces.

I'm sorry your having so much trouble! As another user here asked, do you hear it outside?

The idle noise (when trans engaged) could just be the normal lugging with a interior item rattling?

Can you be more clear about what it sounds like?
Is it a base drum or a snare? is it louder than a average clap?
Does it sound like metal or plastic?
Is it more of a sound you can feel or one you can hear? or both?
(like a real vibration (a problem) is moving somethig that makes noise (not a problem)

I've had similar issues but it was clearly drive shaft related, i ended up buying another slip yoke and having my ds rebuild.

Good luck!
Author:  MACKJ [ Wed May 13, 2009 9:59 pm ]
Post subject: 
Thanks guys for all the feedback and ideas.

BlackLiberty
What could cause an engine miss? I thought it would be a blocked or faulty injector and that is why I had the return flows checked. Are you suggesting it is mainly caused by a compression imbalance?

Nursecosmo
I have basically ruled out tyres and wheels as the vibration is directly related to engine rpms not speed…I may be wrong here but I have had two wheel balances and a wheel alignment.
Yes I will recheck the motor mount tightness.
Yes I will remove the rear shaft and go for a drive.
And I prefer not to imagine I have a Cummins 4BT under the hood!!

ChesterCRD
I cannot hear/feel the vibration outside over the normal diesel clatter.
I have actually had a very high tech vibration analysis (accelerometers and a multi channel analyser) carried out by senior vibration engineers from my work. They have said that the vibration is not normal for a diesel, in fact up to three times the vibration level they would expect for a similar output engine.
The only caveat I have on this data is that the reference standard does not mention four cylinder engines, mostly six cylinders and above. The only bit of data that they have put forward to try to determine the root cause is that the ratio of the high frequency vibration to crank speed is about 147:1. I have been racking my brain as to what could be spinning or firing(?) 147 times faster than crank speed.

CRDMiller
The vibration you can definitely feel, as previously mentioned at idle and a specific rev range.
The noise is more of a low frequency hum, definitely a harmonic being setup through the chassis/body. If I try to hear it with my head around the driver’s feet (not when I am driving, of course!) it is almost imperceptible. The noise is amplified somehow and can best be heard at driver/passenger head level…if that makes sense.
Author:  BlackLibertyCRD [ Wed May 13, 2009 10:40 pm ]
Post subject: 
Just a silly thought, I wonder if the flow control valve flap can hum like a reed with the rush of air going through it when it's wide open. :?: Get a mechanic stethoscope and listen right at the inlet to the intake where the flow control valve is.

BTW Where I work at we had a run on early 4.6 L Crown Vic Police cars that the MAF would Moo Moo like a cow. :-)r
Author:  GoodCRD [ Thu May 14, 2009 12:03 am ]
Post subject:  Engine vibration
If the vibration seems to be coming from the engine first check for a fuel dilution condition. If the engine oil is diluted with fuel have the vehicle towed to a shop and repaired. I'm bringing this up due to my experience with the larger 50 series detroits this little engine shares it design. When you have contaminated engine oil you will damage the bushings in the balance shaft assembly which also contains the oil pump. These bushings fall out due to excessive ware and drop into the oil pan. Signs of this are low oil pressure, overheating, and "vibration". I hope this is not the problem. The assembly is not cheap but is easy to replace.

Good Luck
Author:  ATXKJ [ Thu May 14, 2009 5:36 am ]
Post subject: 
147 times crankshaft speed - sure sounds like a turbo -
but I don't see how a turbo could cause that kind of vibration
Author:  MACKJ [ Thu May 14, 2009 5:37 am ]
Post subject: 
BlackLibertyCRD wrote:
Just a silly thought, I wonder if the flow control valve flap can hum like a reed with the rush of air going through it when it's wide open. :?: Get a mechanic stethoscope and listen right at the inlet to the intake where the flow control valve is.

BTW Where I work at we had a run on early 4.6 L Crown Vic Police cars that the MAF would Moo Moo like a cow. :-)r


Sorry mate, FCV plate has been removed when I blocked off the EGR about 18 months ago.
Author:  mackruss [ Thu May 14, 2009 5:38 am ]
Post subject: 
MACKJ

Good to have you back now let me share what may be a similar experience.

I changed oils from a synthetic to a dino and had this noise appear which i thought perhaps was a turbo bearing. I changed oil back to Mobil 1 Syn and noise has disappeared. I think my problem was lifter related and not very happy with the dino oil.
Author:  MACKJ [ Thu May 14, 2009 5:50 am ]
Post subject:  Re: Engine vibration
GoodCRD wrote:
If the vibration seems to be coming from the engine first check for a fuel dilution condition. If the engine oil is diluted with fuel have the vehicle towed to a shop and repaired. I'm bringing this up due to my experience with the larger 50 series detroits this little engine shares it design. When you have contaminated engine oil you will damage the bushings in the balance shaft assembly which also contains the oil pump. These bushings fall out due to excessive ware and drop into the oil pan. Signs of this are low oil pressure, overheating, and "vibration". I hope this is not the problem. The assembly is not cheap but is easy to replace.

Good Luck


Hi GoodCRD,
Thanks for the input however fortunately I don't have that problem. Just finished a full service with all lubes and the engine oil was just that lovely black colour we all love. Not a hint of any fuel and clean as a whistle...except for the soot.

Hey Mackruss,
How are things with you...yep I haven't been around a while because I have been trying to track down this issue. On the subject of oil I have been running full synthetics since the first oil change four years ago.

BTW this is the best forum I have seen anywhere and I appreciate the wealth of knowledge you all can contribute and I understand it is extremely difficult to diagnose a problem for someone thousands of miles away...but keep the ideas coming :D
Author:  MACKJ [ Thu May 14, 2009 6:07 am ]
Post subject: 
ATXKJ wrote:
147 times crankshaft speed - sure sounds like a turbo -
but I don't see how a turbo could cause that kind of vibration

Yes I was worried about that too but I can't detect any radial or end float outside normal specs...?
It spools up really well. I have no noticeable horsepower loss.
Author:  BlackLibertyCRD [ Thu May 14, 2009 7:13 am ]
Post subject: 
MACKJ wrote:
BlackLibertyCRD wrote:
Just a silly thought, I wonder if the flow control valve flap can hum like a reed with the rush of air going through it when it's wide open. :?: Get a mechanic stethoscope and listen right at the inlet to the intake where the flow control valve is.

BTW Where I work at we had a run on early 4.6 L Crown Vic Police cars that the MAF would Moo Moo like a cow. :-)r


Sorry mate, FCV plate has been removed when I blocked off the EGR about 18 months ago.


Did you just remove the plate and leave the shaft. Is the shaft slotted or is it flat on one end. Maybe remove the whole shaft if it is the problem. I rather see it be a silly problem like this than something serious like a balance shaft. You did say it appear most on driver side lower level. I would probe around that area in the engine bay first.
Author:  Uffe [ Thu May 14, 2009 7:29 am ]
Post subject: 
MACKJ wrote:
Thanks guys for all the feedback and ideas.

ChesterCRD
I cannot hear/feel the vibration outside over the normal diesel clatter.
I have actually had a very high tech vibration analysis (accelerometers and a multi channel analyser) carried out by senior vibration engineers from my work. They have said that the vibration is not normal for a diesel, in fact up to three times the vibration level they would expect for a similar output engine.
The only caveat I have on this data is that the reference standard does not mention four cylinder engines, mostly six cylinders and above. The only bit of data that they have put forward to try to determine the root cause is that the ratio of the high frequency vibration to crank speed is about 147:1. I have been racking my brain as to what could be spinning or firing(?) 147 times faster than crank speed.


147 times crankspeed at 2,000rpm is 4900Hz - that sounds like PWM switching territory to me. That vibration is really at an annoying frequency (at Vestas we use PWM at 5kHz and it is a bugger listening to it.

Do you know the frequency which the guys reported? 147 times crank sounds like turbo, but that could nearly not make such heavy vibrations are you're seeing there. Turbo would also be running at different ratios to crank speed depending on engine load. Turbos are air-pressure driven not belt driven so the ratio of 147 can't be true at all RPMs IF it is the turbo...
Author:  MACKJ [ Thu May 14, 2009 7:31 am ]
Post subject: 
BlackLibertyCRD wrote:
MACKJ wrote:
BlackLibertyCRD wrote:
Just a silly thought, I wonder if the flow control valve flap can hum like a reed with the rush of air going through it when it's wide open. :?: Get a mechanic stethoscope and listen right at the inlet to the intake where the flow control valve is.

BTW Where I work at we had a run on early 4.6 L Crown Vic Police cars that the MAF would Moo Moo like a cow. :-)r


Sorry mate, FCV plate has been removed when I blocked off the EGR about 18 months ago.


Did you just remove the plate and leave the shaft. Is the shaft slotted or is it flat on one end. Maybe remove the whole shaft if it is the problem. I rather see it be a silly problem like this than something serious like a balance shaft. You did say it appear most on driver side lower level. I would probe around that area in the engine bay first.

The shaft is slotted and still there because you have to strip the valve down to remove and I am not sure whether it is just an extension of the motor.
I have and will continue to concentrate on the right hand side of the engine (the drivers side for us Aussies) and the drive train unless someone can throw me in another direction.
I am with you on this one, and I am sure (hoping!) this is something relatively simple. I just can't find it right now :x
Author:  MACKJ [ Thu May 14, 2009 7:41 am ]
Post subject: 
Uffe wrote:
MACKJ wrote:
Thanks guys for all the feedback and ideas.

ChesterCRD
I cannot hear/feel the vibration outside over the normal diesel clatter.
I have actually had a very high tech vibration analysis (accelerometers and a multi channel analyser) carried out by senior vibration engineers from my work. They have said that the vibration is not normal for a diesel, in fact up to three times the vibration level they would expect for a similar output engine.
The only caveat I have on this data is that the reference standard does not mention four cylinder engines, mostly six cylinders and above. The only bit of data that they have put forward to try to determine the root cause is that the ratio of the high frequency vibration to crank speed is about 147:1. I have been racking my brain as to what could be spinning or firing(?) 147 times faster than crank speed.


147 times crankspeed at 2,000rpm is 4900Hz - that sounds like PWM switching territory to me. That vibration is really at an annoying frequency (at Vestas we use PWM at 5kHz and it is a bugger listening to it.

Do you know the frequency which the guys reported? 147 times crank sounds like turbo, but that could nearly not make such heavy vibrations are you're seeing there. Turbo would also be running at different ratios to crank speed depending on engine load. Turbos are air-pressure driven not belt driven so the ratio of 147 can't be true at all RPMs IF it is the turbo...

Hi Uffe,
Glad to see you are still hanging around. The frequency was measured at 1867 Hz. (Frequency of engine at idle was 12.67 Hz =760rpm)
Here are the accelerometer readings also;
Location Vibration level – velocity (mm/s)
Longitudinal Lateral Vertical
Front of sump 2.9 32.7 4.7
Rear of sump 2.2 31.2 2.5
Engine head 0.9 24.3 3.5
Bell housing 1.7 25.6 2.8
Transmission 0.7 22.0 1.1
Transfer case 1.4 9.9 13.9
Author:  MrMopar64 [ Thu May 14, 2009 2:30 pm ]
Post subject: 
I would try to disconnect the exhaust from the turbo and remove from the vehicle. I would also remove all of the skid plates under the front (plate and NVH plastics insert). From here I would start the car and see if the noise is still present. If so, try pushing on the firewall insulation padding and/or anything you can touch that will make it go away - a noise of that magnitude you will find easily.

Also, if you have the vehicle in gear at idle and, with the brakes still pressed, slowly apply the accel pedal and bring the RPMs up, does the noise get worse or go away, then come back? If so, for sure it sounds like somehting rubbing on the firewall or other body structure in the area.

Could also be a broken baffle inside the muffler, or the exhaust otherwise grounding out somewhere along its path. Examine the pipe from front to back, make sure it's not touching anywhere.

Someone that I had talked to some time past with a untraceable NVH issue like that tore apart the whole dash, only to find out that it was something under the hood touching the firewall when the drivetrain was in that "loaded" position.
Author:  MrMopar64 [ Thu May 14, 2009 2:31 pm ]
Post subject: 
I would try to disconnect the exhaust from the turbo and remove from the vehicle. I would also remove all of the skid plates under the front (plate and NVH plastics insert). From here I would start the car and see if the noise is still present. If so, try pushing on the firewall insulation padding and/or anything you can touch that will make it go away - a noise of that magnitude you will find easily.

Also, if you have the vehicle in gear at idle and, with the brakes still pressed, slowly apply the accel pedal and bring the RPMs up, does the noise get worse or go away, then come back? If so, for sure it sounds like somehting rubbing on the firewall or other body structure in the area.

Could also be a broken baffle inside the muffler, or the exhaust otherwise grounding out somewhere along its path. Examine the pipe from front to back, make sure it's not touching anywhere.

Someone that I had talked to some time past with a untraceable NVH issue like that tore apart the whole dash, only to find out that it was something under the hood touching the firewall when the drivetrain was in that "loaded" position.
Author:  MrMopar64 [ Thu May 14, 2009 2:33 pm ]
Post subject: 
I would try to disconnect the exhaust from the turbo and remove from the vehicle. I would also remove all of the skid plates under the front (plate and NVH plastics insert). From here I would start the car and see if the noise is still present. If so, try pushing on the firewall insulation padding and/or anything you can touch that will make it go away - a noise of that magnitude you will find easily.

Also, if you have the vehicle in gear at idle and, with the brakes still pressed, slowly apply the accel pedal and bring the RPMs up, does the noise get worse or go away, then come back? If so, for sure it sounds like somehting rubbing on the firewall or other body structure in the area.

Could also be a broken baffle inside the muffler, or the exhaust otherwise grounding out somewhere along its path. Examine the pipe from front to back, make sure it's not touching anywhere.

Someone that I had talked to some time past with a untraceable NVH issue like that tore apart the whole dash, only to find out that it was something under the hood touching the firewall when the drivetrain was in that "loaded" position.
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