Chasing a vibration for 1 year

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ShaneJeepTJ

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California
I've owned my 2001 Jeep TJ for almost a year now. It's a 6 Cylinder with 170k miles and 3-Speed Automatic Transmission. When the Jeep is at a full stop and I put it in Drive or Reverse the shaking/vibration is so bad I can barely see out of the mirrors. When it's in park or neutral there is almost no shaking. The shaking/vibrations does not change with the Air Conditioning On or Off. Since the TJ is not moving when this happens it's not the suspension, wheels etc. The shaking is not noticeable after I accelerate. To date I've done the following to attempt to address this.

- Install Brown Dog Engine Mounts with Ultra Flex Rubber Bushings
- Replace the transmission mount with new OEM
- New 4 hole Bosch fuel injectors
- New Autolite Iridium XP plugs
- Cleaned the throttle body and sensors
- Auto Transmission Fluid replaced by shop
- New timing chain
- New water pump/radiator/thermostat
- Factory Air Box with new K&N Filter

Nothing I've done to date has helped fix this. I know this has been discussed multiple times in these forums and I've gone through all the posts and am at a loss. Please provide suggestions and feedback.
 
Was Brown Dog engine mounts a response to vibration, or did vibration started after you installed them? They are known for passing engine vibes into cabin.
 
Shot in the dark here, but harmonic balancer maybe? (the one on the crank snout)

Seems to me that you have replaced all the mounts with quality replacements (the Brown dogs are stiffer than OE, but shouldn't shake your mirrors, I have them) so I would be assuming that the drivetrain has a vibration that it shouldn't, rather than is transferring a normal vibration to the passenger compartment.

A video of the vibe would really help us, both from the drivers seat and if you can from the outside of the Jeep.
 
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could also be a really poorly balanced flex-plate/torque converter, if you have had any work done there around the start of the problem.
 
I 2nd torque converter. It will definitely cause a first order vibration like what you've described.
 
eastbloc said:
Was Brown Dog engine mounts a response to vibration, or did vibration started after you installed them? They are known for passing engine vibes into cabin.
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The vibration was always there. The engine mounts were original and I replaced them with Brown Dogs. It did not help or make the vibration worse.
 
Another observation I just had was the RPM's. When in neutral the RPM's are at about 800. When I put it in drive/reverse the RPM's drop down a bit and the vibration starts. If I put my left foot on the brake and use the right to increase the RPM's back up to 800 the vibrations stop. What controls the RPM's? What RPM's do you recommend for a straight 6?
 
ShaneJeepTJ said:
Another observation I just had was the RPM's. When in neutral the RPM's are at about 800. When I put it in drive/reverse the RPM's drop down a bit and the vibration starts. If I put my left foot on the brake and use the right to increase the RPM's back up to 800 the vibrations stop. What controls the RPM's? What RPM's do you recommend for a straight 6?
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PCM controls idle RPM’s

But it taking inputs from various sensors around the intake and throttle body.

Unmetered air entering the engine, it cant account for.
 
Im going to say its a 4.0 AMC 6 cylinder thing that is inherent and you will not be able to get rid of it.

The AMC 6 cylinder just doesn't run super smooth compared to other makes in my experience.

I have a 98 TJ with a 4.0 and 32rh with about 40k miles on it and the same vibe issue you describe. It is what it is.
 
Get rid of the brown dogs. You may have had vibes before but with the brown dogs you will now never know if you solve the vibes because the brown dogs will cause vibes forever.

You may have had “stock” looking mounts that were the hard as rock parts store rubber mounts. Those pass vibes badly. My next step would be a set of fresh Mopar 52019278AD mounts. And if you didn’t actually get an OEM Mopar trans mount, get that too. If you got actual mopar then you’re good there.

If the mounts don’t fix it then I’d definitely check out the torque converter. But the brown dogs need to go.
 
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machoheadgames said:
Get rid of the brown dogs. You may have had vibes before but with the brown dogs you will now never know if you solve the vibes because the brown dogs will cause vibes forever.

You may have had “stock” looking mounts that were the hard as rock parts store rubber mounts. Those pass vibes badly. My next step would be a set of fresh Mopar 52019278AD mounts. And if you didn’t actually get an OEM Mopar trans mount, get that too. If you got actual mopar then you’re good there.

If the mounts don’t fix it then I’d definitely check out the torque converter. But the brown dogs need to go.
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I'll admit mine is stick, so its a little different, but I have never had problems with vibes using the RUBBER brown-dogs, I have heard some horrible things about the Polys and I think BD themselves even admit those mounts are stiff and for racing application only, but the rubbers have been great to me. - Im not really ready to accept the idea. that the BD mounts are transferring that much vibe and that swapping them out will make the problem all better, exaggerating an existing problem...... possibly but I think you have a root vibration in the chassis that should not be there, just my 2 cents

You could look at the IAC for possibly having to low of idle, or maybe a vacuum leak but 750RPM is about right for what I see (again, stick, so might be a little different)

Again, video would be great if you can swing it :)
 
KingCarGuyZ said:
I'll admit mine is stick, so its a little different, but I have never had problems with vibes using the RUBBER brown-dogs, I have heard some horrible things about the Polys and I think BD themselves even admit those mounts are stiff and for racing application only, but the rubbers have been great to me. - Im not really ready to accept the idea. that the BD mounts are transferring that much vibe and that swapping them out will make the problem all better, exaggerating an existing problem...... possibly but I think you have a root vibration in the chassis that should not be there, just my 2 cents

You could look at the IAC for possibly having to low of idle, or maybe a vacuum leak but 750RPM is about right for what I see (again, stick, so might be a little different)

Again, video would be great if you can swing it :)
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I have a stick too, and it’s not as bad as an auto. However even on the stick, the brown dogs transmit a lot of vibes. You’d be surprised if you went back. We get used to it over time. I drove brown dogs for 4 years and wanted to like them. It’s pretty easy to see why they would cause vibes, you have like 10x the amount of rubber in the stock mount.

And for what it’s worth, I ran brown dog rubber and poly both, and neither of them were really any different.
 
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machoheadgames said:
You can not even tighten the through bolts at all and they will still cause vibes. You need a back to stock comparison and your eyes will be opened. Tons and tons of people say the same thing. Yours aren’t magical.
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Bro... I have had both setups.

The only time I had a vibe caused by the brown dog motor mount was when it was too tight.

Even too loose and you will experience a diff type vibe. Needs to be the right torque.

I believe you had vibes, and that those motor mounts can cause vibes. But to absolutely say they all do is absurd... especially when others who have them say they can work.

Just because "tons and tons of people say the same thing" doesn't make your statement fact.

That is called a bandwagon argument... which is a logical fallacy.

Let's strive for accurate information, and not parrot the popular sentiment for the day.

Or maybe mine are magical.. I did pay for the pixie dust powder coating.
 
Sancho said:
Just because "tons and tons of people say the same thing" doesn't make your statement fact.
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If tons and tons are sharing their experience - that is exactly what fact is, and you have supported his stated fact with 1st two lines of your reply.

Sancho said:
That is called a bandwagon argument... which is a logical fallacy.
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Personal exception to the general rule, does not negate or change the general rule... That is a delusional female logic.

Sancho said:
Let's strive for accurate information, and not parrot the popular sentiment for the day.
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Any time bud, waiting on you

Sancho said:
Or maybe mine are magical.. I did pay for the pixie dust powder coating.
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Maybe, did you chose rainbow color coating design, and were the mounts referred to with 3 different pronouns in the instructions?
 
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I appreciate all the comments. I loosened the through bolt on the Brown Dog Engine Mounts a bit and the vibrations continue.

I’ve been reading about how Torque Converters work. The Impeller side of a torque converter is connected to the crankshaft and spins all the time. The vibrations don’t happen when the car is in Park or Neutral so that should rule out the Impeller side. Then there is the Turbine side and when I am at a stop light I have the brake fully depressed. That should stop the Turbine side from spinning but the vibrations still happens and the Turbine isn’t spinning. Am I on the right track here?

What about the IAC and PCM? I’ve added new 4 hole Bosch injectors, new plugs and a K&N Filter in the original housing. I’ve cleaned the IAC but do they go bad?
 
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