Engine/Cabin Vibration

[TripleC321]

22 hours ago, Ronnie said:

I would connect a timing light to a plug wire and shine it on the balancer. Sometimes doing that will make moving parts on an engine look like they are moving in slow motion. If it is wobbling you might be able to detect it by doing that.

So, I’m still pretty new to this working on my own car thing. I’ve not ever done the procedure as you’re describing. 
 

so is performing that test the next step I need to take or am I missing an intermediate step?

[Ronnie]

Using the timing light was just a suggestion. I don't know if it would even be helpful. Most people don't own timing light the days since they aren't needed on most new cars. 

[TripleC321]

Gotcha. I can supposedly acquire on at my local harbor freight if needed. 
 

just unsure what the next steps I should take are to chase down this vibration. It’s just weird cause it only occurs in a specific RPM range. 

[DAVES89]

I would check the corner supports that go over the battery and air cleaner to be sure they are both there and tight.

[TripleC321]

11 minutes ago, DAVES89 said:

I would check the corner supports that go over the battery and air cleaner to be sure they are both there and tight.

The two supper bars that go from strut mount to front frame? Yes they are present and right. 

[2seater]

Is there any way to quantify the frequency of the vibration when it is most apparent? I think I suggested trying a vibration app for your phone in another forum. Admittedly, I haven't tried such myself, but there are lots of free apps to analyze vibration or frequency. Does any sound accompany the vibration? 

[ship]

Have you examined the motor mounts/tranny mounts that might be warn/broken? I once had a '97 Riviera that vibrated right up through the steering column: cause was a broken motor mount.  With the engine off, try shaking/rocking by hand the engine in place...any real movement?

[TripleC321]

1 hour ago, 2seater said:

Is there any way to quantify the frequency of the vibration when it is most apparent? I think I suggested trying a vibration app for your phone in another forum. Admittedly, I haven't tried such myself, but there are lots of free apps to analyze vibration or frequency. Does any sound accompany the vibration? 

Ask and you shall receive. Although I can't post them direct here. I've included a link to a shared iCloud folder that holds the frequency measurements, as well as a short video of the belt area while under load, in case it might be useful.

 

I took 8 total measurements. 2 at each RPM point. One with a foam block between the phone, and one with direct phone contact. All points of contact were the top of the intake manifold. phone was positioned landscape mode, perpendicular to the intake manifold (making a + sign essentially).

 

I have no idea of the data I took is useful, or if I even had the app set to measure the correct things. it has lots of options. So if I need to remeasure with different app settings let me know.

 

https://www.icloud.com/iclouddrive/0f6rrM_wu9jWZ3A3cO1WneBCQ#Reatta_Frequency

[TripleC321]

10 minutes ago, ship said:

Have you examined the motor mounts/tranny mounts that might be warn/broken? I once had a '97 Riviera that vibrated right up through the steering column: cause was a broken motor mount.  With the engine off, try shaking/rocking by hand the engine in place...any real movement?

All mounts have been replaced. I am not able to move the motor by hand.

[TripleC321]

https://share.icloud.com/photos/02eBS2JjQ_86oqYiU_MCEY-VA
 

here is another link to a different video. There’s an interesting sound for the first few seconds as it sits at idle. You can hear a variation of other sounds as I rev it a little bit too. 

[TripleC321]

And here’s 3 more videos that might help, technology is wonderful. 
 

1 taken at 240 fps slo mo: https://share.icloud.com/photos/0d0UPSC-A181i_uabJDkPP8yQ

 

1 taken at 120 fps slo mo: https://share.icloud.com/photos/0e78C8po8bxexWWweh4mtNW1Q

 

and another taken in normal video mode, but at 24fps: https://share.icloud.com/photos/003ljmheph2NGnYxLsw3OWDKw

 

maybe these can help? In theory accomplishes the same thing as Ronnie’s earlier timing light suggestion?

[2seater]

I viewed the stuff that I could but honestly, I can't tell much. The data from the vibration files is just lists of numbers and symbols, so not much there. The videos are better, but I only saw the engine seemingly move for just a second, the rest seems pretty normal sound wise. I think maybe Ronnie's suggestion of the timing light is a good one. Essentially we are looking at a strobe light that will give stop action type views. A dial back type light would allow the light flash to be moved around a little bit earlier or later to observe what's going on. Thanks for the information but I am not much help.

[TripleC321]

The values the files five are the coordinates on a graph. X,Y,Z coordinates. Unfortunately that seems to be the only way the app exports them, even though it shows a graph when measuring. 
 

what frequency should I be looking for?

[DAVES89]

Stupid question but did you ever check the balance of the tires?

[jon L]

I assume that you have already checked the harmonic balancer.

Could it be coming apart?

Edited June 14, 2023 by jon L

[TripleC321]

27 minutes ago, DAVES89 said:

Stupid question but did you ever check the balance of the tires?

Yes, but even if they weren’t balanced, they’d have no effect at idle, where the vibration still occurs. 

[TripleC321]

17 minutes ago, jon L said:

I assume that you have already checked the harmonic balancer.

Could it be coming apart?

I don’t really know how to check it other than just visually. 
 

the harmonic balancer has been an open ended question people have been proposing here, with nobody really knowing if it is or isn’t the cause. 

[Ronnie]

2 minutes ago, TripleC321 said:

I don’t really know how to check it other than just visually. 
 

the harmonic balancer has been an open ended question people have been proposing here, with nobody really knowing if it is or isn’t the cause. 

Are you hearing any knocking or rattling sounds at idle? Common if the balancer is bad.

[TripleC321]

1 hour ago, Ronnie said:

Are you hearing any knocking or rattling sounds at idle? Common if the balancer is bad.

I did notice a very very very light “slap” when it was at 900 RPM. 
 

I’ve had a balanced go bad before on the old engine and it was really easy to tell the balancer was bad. Not at all like this one, 

if it is indeed the balancer

[2seater]

Okay, scratch all the app suggestions unless you can figure out what it is telling us, and I am sorry for the suggestion. I tried three vibration analyzers and two sonic meters but I cannot tell what they are trying to tell me. For example, phone laying on front valve cover showing 50Hz at idle. Rev the engine a little and the frequency goes down, not up, so whatever it feels is outside of my frame of reference😖

 

I found my cheap mechanics stethoscope is probably more help. Listen to everything to see if something matches the rhythm of the vibration. You can touch anything except physically moving parts, even the bolt in the middle of a tensioner wheel, anything fixed in place. I am pretty hard of hearing but I can hear valves closing and some internal engine sounds.