Chasing a vibration for 1 year

[KingCarGuyZ]

IAC’s can go bad, but normally cleaning would fix them at least temporarily, maybe a TPS/vacuum leak if you are concerned with low idle speed. But I don’t think that’s it. I’m sticking with maybe crank balancer. - suppose it could still be the torque converter being weird, maybe a concentric input shaft bearing? - that last one is a definite shot in the dark.

 

[machoheadgames]

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?

Loosening the bolts doesn’t prove anything. What I said previously is loosening them will still pass along vibes because even in loose form, the rubber in those mounts is so thin it provides hardly any isolation. Seriously, consider going back to stock so you can have a real way to evaluate the condition of the Jeep.

An automatic will naturally have more vibrations at idle in drive due to the driveline being connected; i.e. the impeller turning while the turbine does not. This is why auto owners with aftermarket mounts traditionally hate them. The manuals aren’t as bad as they’re always in neutral at lights or anytime parked with engine running. Yes, vibration in drive signifies that it’s torque converter/auto related but with an automatic you’ll feel it much more due to the brown dogs or any aftermarket mount.

You’re idling at 750-800, that’s normal and that signifies the IAC is fine and so is the PCM running it.

 

[ShaneJeepTJ]

I appreciate the feedback from everyone. I really thought Brown Dogs were the way to go but I am going with your expertise guidance. The Brown Dogs were such a pain to get in as well. I'll source some factory engine mounts and report back.

 

[Sancho]

I appreciate the feedback from everyone. I really thought Brown Dogs were the way to go but I am going with your expertise guidance. The Brown Dogs were such a pain to get in as well. I'll source some factory engine mounts and report back.

Where in CA are ya, as I have some spare factory mounts. If in San Diego.. let me know and you can swing by.

Also... assuming the vibes are from the mounts... try to tighten the bolts and see if that changes the vibes.
When I installed mine... they were too loose... which gave it a more violent shake. I over tightened and the vibes were more acute but still there. I then back it off a smidge and problem solved.

Aside from the violent shaking...where are you feeling the vibrations? Pedal? Steering wheel? seat?

 

[Wingback73]

If the vibration goes away when you isolate to a single variable (Park/Neutral vs Drive), then whatever the last variable you changed was the issue.

Brown Dog or not, you already gave the answer earlier in the thread. When you are in drive the RPM's drop. But when you put your foot on the gas to bring them back up to the same RPM when in Park/Neutral they go away. ONLY in that scenario do you have a valid, 1 variable comparison.

The problem is that your engine is idling low when in Drive and the 6 is out of balance at that point. Can the bushing solves that problem? Maybe, but it depends on how bad the vibration is. I have the same thing in my 2006 manual - my idle is low enough that I get a vibration. Bump the gas and it goes away. Clearly not the transmission since I'm stopped. So must be the engine, just like yours. Could be the bushings, but yeah, that's a pain in the ass.

d-

 

[ShaneJeepTJ]

Thanks Sancho for the offer but I live in the SF Bay Area. I feel the vibration in the Steering Wheel and Seat. I see it in the Drivers Mirror and Rearview Mirror, but not as much in the passenger mirror.

I was just driving it and experimenting. I think the throttle may be a bit low. When I am at a stop light and left foot the brake and push the gas just a tiny bit the vibrations completely stop. It's like the idle is too low. Back in the 1980's I'd just adjust the idle a bit higher. What's the process to do this with the Jeep?

When the car is in Park or Neutral the idle is maybe ~800 with no vibrations at all. Then when I shift to Drive/Reverse the idle drops about ~50 to ~750 and the vibrations starts up. I made sure to have the AC off and Fan off. Vacuum leak maybe?

 

[Sancho]

Thanks Sancho for the offer but I live in the SF Bay Area. I feel the vibration in the Steering Wheel and Seat. I see it in the Drivers Mirror and Rearview Mirror, but not as much in the passenger mirror.

I was just driving it and experimenting. I think the throttle may be a bit low. When I am at a stop light and left foot the brake and push the gas just a tiny bit the vibrations completely stop. It's like the idle is too low. Back in the 1980's I'd just adjust the idle a bit higher. What's the process to do this with the Jeep?

When the car is in Park or Neutral the idle is maybe ~800 with no vibrations at all. Then when I shift to Drive/Reverse the idle drops about ~50 to ~750 and the vibrations starts up. I made sure to have the AC off and Fan off. Vacuum leak maybe?

Maybe.

The idle rpm sounds about right tho. My sentiment is similar as others have mentioned.... could be the balancer.. trans mounts.. or motor mounts. In that order.

The motor mounts might be observable.

When mine were too loose... I could and hear the issue.

 

[ShaneJeepTJ]

Update: I replaced the IAC and TPS that are on the throttle body. Both old sensors had the Mopar stamp on them and appeared original to the vehicle. Then I reset the PCM by disconnecting the battery overnight. The vehicle shaking when in Drive or Reverse is significantly better especially when the air conditioning is off. I'd call the problem resolved. I'm still going to source original engine mounts.

Thank you WranglerTJForum.com for all the valuable posts and information from all the subject matter experts and Jeep enthusiasts.

 

[Courtglau]

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.

I also have a TJ 2001, I’ve had issues with it shaking over the first 2 years I had it. It would violently shake and it turned out to be the ECM sending out faulty Fuel injector misfires. Had it send out to a shop in Florida to do a repair and haven’t had issues since!!