How many owners have noticed engine vibration (around 2500 rpms)?

[Triathlete]

I had the pleasure of meeting Jerry last year in Moab. The guy will totally boggle your mind with the info he has in his head. I think the guy has every bit of Zu info memorized...truley amazing!!!!

[RamAirZ]

Ya he's an awesome guy! His trooper is one hell of a sleeper too lol

[SuperBoomTurbo]

i have so much vibration that I cant stop driving it around......especially since Moab.....vibration AND grinding!

You must be a nurse, right?

[SuperBoomTurbo]

For the actual post: especially in the body on frame cars of japanese origin, the motor mount Spacers were made of soft squishy rubber that all came from the same supplier. These are not like the indestructible urethane aftermarket type. After lots of hard revving or even just years of weather exposure (high heat, road salt, etc) they break down like wiper blades.

With that in mind, its easy to test. With the engine off, go push on it side to side and see how much wiggle you get. With the engine on, leave it in park (of course) and blip the throttle body through short rev ranges. Bet it moves a lot if your mounts are trashed! As the rpm's climb, the engine movement settles down as all the torque presses the engine down on the mounts.

I drove a '90 240sx for years with this same issue and didn't notice a problem mechanically til I swapped the transmission. It'd shake and shimmy at stoplights like it had a blown hemi under the hood, resulting in the occasional 'seat wood'. (TMI!!) though the lady passenger of the time didn't seem to mind.

Now if your motor vibrates when doing highway speed like something is about to explode under there (ie under load), that sounds quite a bit more complicated, and in which case, you will soon see money flowing down the street behind you in the form of engine internals becoming externals...

[RamAirZ]

Putting it in drive with your foot on the brake and giving it a little rev with someone watching will REALLY show you, when my Mustang's mounts went bad, the motor looked like it wanted to crawl out of the engine bay.

[89Vette]

Then don't buy a vehicle that has a 75 degree V6 with no balance shaft! The 6VE1 is always going to feel a little uncivilized...

Are you sh'ing me? Motors (cranks) don't have a balance shaft. They have counterweights on the crankshaft.

Should I check my muffler bearings too?

[SuperBoomTurbo]

...when my Mustang's mounts went bad, the motor looked like it wanted to crawl out of the engine bay.

Off topic, but do you remember that pennzoil commerical a few years back where the chevy 'burb did a wheelstand before launching the motor like a cannonball? I was working with a 60 year old mopar man who shart himself after watching it via youtube.

T/j over

[RamAirZ]

Are you sh'ing me? Motors (cranks) don't have a balance shaft. They have counterweights on the crankshaft.

Should I check my muffler bearings too?

Balance shafts go in the top of the engine, usually in the lifter/intake valley, here is a 4.3 V6 balance shaft:



Not all motors have/need them but they are used in some.

And yes I've seen that commercial, it's pretty funny lol

[SuperBoomTurbo]

This isn't it, but still damn funny. Trying to lighten the mood, y'all!

http://www.youtube.com/watch?v=J3FIZR8Sp6w

[89Vette]

Balance shafts go in the top of the engine, usually in the lifter/intake valley, here is a 4.3 V6 balance shaft...Not all motors have/need them but they are used in some.

Well, that's a new one on me!

What does a balance shaft "balance". I saw an exploded view of the 3.5L and the crank appears to have the tradional counterweight lobes. Why wouldn't that balance the rotating assembly?

Why build an engine with "extra" vibration if it could have been avoided with this part?

[RamAirZ]

Well alot of it has to do with packaging, parts interchangeability, a certain goal they are trying to reach etc., and like with 4 cylinders, sometime it's just something you have to do. The 4.3's didn't start off with a balance shaft but they ended up going to one to try and smooth out vibrations. All crankshafts have counterweights but sometimes the design of the engine and the firing sequence can produce unwanted vibrations. Take the 4.3 for example, it's basically a 350 chevy with 2 cylinders chopped off. But due to the firing sequence, it's a shaker! In a V8 it works fine but in the V6 it makes it lopey. Here's a good read:

http://en.wikipedia.org/wiki/Balance_shaft

[89Vette]

Here's a good read:

http://en.wikipedia.org/wiki/Balance_shaft

Thanks. I note this paragraph at the end of the link....

"Another balance shaft design is found in many V6 engines. While an inherently balanced V6 engine would have either 60 or 120 degrees angle between the two banks of cylinders, many current V6 engines are derived from older V8 engines, which have a 90 degree angle between the two banks of cylinders. While this provides for an evenly spaced firing order in an 8 cylinder engine, in a six cylinder engine this results in a loping rhythm, where during each rotation of the crankshaft three cylinders fire at 90 degree intervals, followed by a gap of 90 degrees with no power pulse. This can be eliminated by using a more complex, and expensive, crankshaft which alters the relationship between the cylinders in the two banks to give an effective 60 degree difference, but recently many manufacturers have found it more economical to adapt the balance shaft concept, using a single shaft with counterweights spaced so as to provide a vibration which cancels out the shake inherent in the 90 degree V6."

The last couple of sentences seem to explain why some engines have a balance shaft and why the VX does not. I just noticed this evening that the 3.5L crankshaft sells for over $1000!

Since I doubt this is an availability thing (because the 3.5L was in other vehicles), I would appear a more expensive crank -- referred to in Wikipedia -- has been utilized in the VX. IOW, it doesn't have a balance shaft because it doesn't need one.

[RamAirZ]

Well NEED is a term used loosely by auto manufacturers lol. I don't think the engine needs one per se but like I stated earlier, I've driven alot rougher engines (due to my own choices). I'm not sure if the 3.5 actually uses the style of crankshaft they mention, it could just be expensive because it's not a "common" engine and specific to only one engine, which makes the market for it low, thus costing more.

[deermagnet]

I have an Isuzu tech training course for these engines and this is what it says-
Problem- Engine has a vibration at above idle.
Possible cause- Outer ring on the harmonic damper has moved.
Diagnosis- Look for abnormal harmonic damper oscillations. During a visual inspection, check to see if the inner damper spring is also damaged.

I checked the parts catalog and repair manual and can't find any info on the damper/balancer.

I don't believe it's normal for this engine to vibrate at all. In over ten years on the Vehicross forums this is the first time I've heard about any engine vibration. Mine is so smooth with 218,000 miles and at 80 mph my whole vehicle doesn't have even the slightest vibration.

Engine vibration on this 3.5L should be something that can be corrected, IF the problem can be found.

Mark Griffin

[RamAirZ]

Well also a vibration to one person might not be one at all to another. So it's hard to say. But it's very easy for any engine to vibrate when mounts go bad, which they can/will do over time. Like you said, should be able to be corrected. I'm thinking mounts or balancer, I know the earlier 3.2 had balancer issues.