Engine Vibration

[gstacky]

Hey guys, wondering if anyone else has had this issue, or can think of anything else to look for.

I just rebuild a Ty engine and put it into my truck. At 1800 rpm up to about 2100, the engine has a pretty decent vibration. Anything higher or lower and it goes away. I have pulled the torque converter back, still there. Changed the flywheel with another from a 4.3, still there. Pull the belt off, checked to make sure there was no contact of anything with any body or frame, all is good. It has brand new rubber mounts everywhere, JTR 2.8 kit on the engine, and brand new transmission mount.

This engine is in a 2wd truck, not that it should make a difference.

Driving it down the road, it runs and drives great, but vibrates as it comes through that rpm range.

I have had it one datamaster briefly, and it was showing some knock as it came up to that rpm area.

Any ideas are appreciated, I don't know what else it could be.

 

[Slyclone]

Re: Engine Vibration

You think the balance on crank is right?

How about the actual harmonic balancer condition? The front is full of little weights pressed in. Some could be missing.

I am expirence a vibration as well but believe it is drive line related.

 

[IGottaSy]

Re: Engine Vibration

TPS faulty or dirty contacts? What does DM show for injector pulse when it happens? Just giving you ideas.
I would rule out front suspension condition/parts or u-joints.

 

[gstacky]

Re: Engine Vibration

According to my engine guy the cranks aren't balanced, any balancing is done through the flywheel and balancer.
I guess the balancer is next to pull and replace, that's all there is left without it being something inside.
The engine was just freshened up, new bearings, new cam.

It's definitely not front suspension, it does this in park.

 

[Don W.]

Re: Engine Vibration

According to my engine guy the cranks aren't balanced, any balancing is done through the flywheel and balancer.

Maybe you find a new engine guy rather quickly. Balancing includes everything that's moving with the crankshaft, including the crank itself. Rods (including bearings), Pistons (including rings and pins), dampener, and flex plate. Our engines are externally balanced. Meaning there are weights on the flexplate which is why it has to be included. To late now but if you look at the crank it will have holes drilled in the counterweights for balance.

When you say flywheel I assume you mean flexplate. If the engine was just rebuilt and the rotating assembly not modified in any way then it should have retained its factory balance. Meaning the other suggestions may apply.

As I understand it the little holes in the dampener which may or may not be filled are used to "fine tune" the balance when the engine was run the first time at the factory. If so then our dampeners are unique to each engine.

 

[gstacky]

Re: Engine Vibration

Thanks for the reply Don

Yes everything is original as far as I know to this engine, and I think what the engine builder meant is that the original crank and all parts related to it would have been set up factory, and not balanced or needed to be balanced after that. The bearings were changed, other than that, everything else was OE, he may have done rings, I'm not 100% sure, but the pistons, rods and crank are all the originals.

Flywheel....it's Monday morning, yup I mean flexplate. Like mentioned, I have tried 2 from 4.3's and neither made a difference.

The balancer is original, I didn't change it, and I doubt he did either, but it's all that seems left that I can think of.

 

[Don W.]

Re: Engine Vibration

OK, good. If it's not to late put the original flexplate back on and, while parked, run a DM through the vibration range. Post it if you can. If, like you said originally it vibrates while disconnected from the trans then it's the motor. Question is why.

Sorry, but are you sure it's not a miss of some sort?

Without a balance shaft a 90* V6 is very difficult to balance.

https://en.wikipedia.org/wiki/V6_engine#Balance_and_smoothness

A few years ago I did a complete overhaul of a Buick odd fire V6 from a Jeep. Although you could hear the odd fire at idle it ran well and was very smooth above idle.

Of course none of this explains your issue...:roll:

 

[NOJIMMY]

Re: Engine Vibration

The following may not be that helpful, but when I hear about vibration issues:

• I try to isolate between the driveline and the motor; idle vs driving vs acceleration rpms; and constant or intermittent conditions.
  
• I inspect items like motor mounts, tranny mounts, ignition misses, propshaft/joint issues or flexplate problems (bent, balance problems, missing bolts).
• I would check the obvious (serpintene/accessory components, dampner and rotating mechanical parts).
• And isolate as much as possible to diagnose (inspecting starter/solenoid mounting, or newly installed parts for when the events began).

It may require swapping out or running your vehicle while on jack stands to spot.


-Larry

 

[gstacky]

Re: Engine Vibration

Been there done all of that Larry, it's narrowed down to the engine for sure, not drivetrain, not motor mounts, took the belt off, pried underneath on everything with a pry bar, no difference. I'll have to check every ignition part piece by piece and hope I find something wrong. Everything is new, but I'll ohm out the wires, just to see. I've gapped the plugs at .35 and now at about .40, no difference, and they all looked good, I'll keep playing hoping that it's ignition. I may pull the balancer just to see if that changes it too.

 

[NOJIMMY]

Re: Engine Vibration

Maybe one of the experts can chime in at this point, but if its not these:

• Worn Out Spark Plugs, wires, ignition module, or coil
  
• Loose or Disconnected vacuum Hoses
• Broken Motor Mounts, exhaust manifolds
• Faulty or Poorly Adjusted Fuel Intake/Injector System
• Bent accessory belt pulleys, dampner, Faulty Timing Gear/chain or
• the fuel supply, air intake system or electronics/computer systems related.

Perhaps a failed or dirty mass air flow sensor, a clogged filter, bad pump, or fuel pressure regulator or bad gas is the culprit. Lastly a bad camshaft, crankshaft, MAF or MAP Sensor and even a broken piston ring, blown head gasket, or valve-train issues can cause vibration.

But it seems as though you've thought this through pretty well unfortunately. Don't know if a compression check would reveal any clues (cylinder related) either.

-Larry

http://www.ehow.com/how_2060649_stop-engine-vibration.html

 

[Don W.]

Re: Engine Vibration

There is no mass air flow sensor in a stock Sy engine. A compression check is a good idea. I like to just crank the engine, with ign or fuel disabled so it won't start, and listen. Does it sound the same as it rotates through each cyl? A leakdown test might be in order. I've seen a leakdown find a broken exhaust valve seat when the compression check didn't.

 

[Davemc1963]

Re: Engine Vibration

The front dampener is 'Neutral balanced' or at least I believe it should be. It may be worth checking that the outer ring hasn't slipped. Based on what others and myself have found, it will slip one day and you will either not be able to time it correctly, or even at all. I was in denial with mine, as checking it was one of the first things I did using a home made piston stop and it was spot on. However, it did slip eventually, by quite a bit, and when I removed the dampener, the outer ring didn't take much persuasion to come adrift from the elastomer ring. For what its worth, if its the original one, I would replace it anyway. $35 from Rockauto. If it has slipped, and it is timed wrong, it could be that the timing curve in the ecu at that rpm, with the 'basic' timing setting that you have set is making for an unhappy engine at that rpm range. If you disconnect the EST tan/black wire, although it will run rough, does it still vibrate? That may rule this out as the problem, but I would still replace it anyway if its the original.

 

[gstacky]

Re: Engine Vibration

I think the balancer is my next move. I drove it this morning, and aside from the vibration, the engine seems to work really well.

Every ignition part is new, distributor, coil, cap, rotor, wires, plugs, and I pulled the plugs after it ran a bit and they all look the same.

Fuel pump is a new 255lpm from racetronix, with the upgraded wiring, the fuel pressure regulator is new too.

Engine has new bearings, rings, and cam, original pistons, rods and crank.

Keep the ideas coming, hopefully I can update soon with any progress.

 

[Don W.]

Re: Engine Vibration

You could experiment with running it without the damper. It would remain to be seen how much oil would get out. For the brief period that it would be running maybe not much?? It would be quick test if it didn't make to much of a mess.

Is the vibration there when you start from cold? Or does it begin after it warms up a bit. Following other suggestions I was wondering if the vibration changes when it goes from open loop to closed.

 

[gstacky]

Re: Engine Vibration

It's always there, from the moment you start the engine.

 

[ed hess]

Re: Engine Vibration

my first motor had been internally balanced. Had the same issue. So i got this bright idea to remove the weight on the B&M flexplate I put on it. Guess what. No more vibration. Just a thought.

 

[gstacky]

Re: Engine Vibration

I've given that some thought Ed, I'm just pretty sure this one isn't internally balanced, but maybe something in the rebuild process is causing the issue.

 

[ed hess]

Re: Engine Vibration

Pretty sure or exactly sure makes a difference. Ask the machine shop or previous owner.

 

[Don W.]

Re: Engine Vibration

If I have my info correct balancing our engines internally would require adding wight to the counterweight(s). Very expensive. Certainly worth a shot though. Will a non weighted flexplate from a Chev V8 fit?

 

[ed hess]

Re: Engine Vibration

Internally balancing is done with adding the metal thru the crank counter weights. In my case a simple die grinder at the tack welds holding the weight to the flexplate was all that was need.