Strong Engine Vibration...3400-3900RPM Need some assistance please!

TGPilot · 07-11-2005

Hey folks...

I know this has always been there since I bought the car in December 04...but it is driving me nutso lately.

My 94 TSi has an engine vibration that is pretty damn strong but only between 3400 and 3900 RPM on the stock tach. This vibration is just as strong in any gear under load or not. When on the other side of this RPM range it is SMOOTH as glass! Especially at highway speeds above 4000 RPM it is quiet, smooth and quick to respond to added throttle. Only problem is speed limits here in Colorado are 75MPH and 4000RPM in 5th is just a tick past 85 and the State Patrol don't normally let 10 MPH over slip by!!

Any help or ideas as to what this is would be great. It is about 25k miles away from needing a timing belt and thought maybe the balance shaft or it's belt might be at fault. When I had the oil pan dropped I grabbed the balance shaft and tried to twist it and there was ZERO play in the shaft so I am assuming the belt is ok...

TheBlizzard · 07-11-2005

I would say that the balance shaft is off a little bit. JET had it happen to his car few times and it did the same thing that you are describing. Your going to have to tear it apart and look either way to tell.

TGPilot · 07-11-2005

Craig...

Two questions for you.

1). Should this be done right away (has been 6 months like this) to avoid possible engine failure?

2). I know the timing belt needs/should be done at the same time...can this be done in the car or should the engine/tranny come out to do it. Obviously it would be easier access...but is it necessary to remove the engine/tranny?

Thanks!

-Kenny

**JET** · 07-11-2005

No, you can do it with the engine in the car. It isn't a real problem. I would do it soon. There have been reports of bearing failures on cars with the balance shaft off. It takes a few hours to do, but isn't terrible. If you need to replace the Bbelt soon anyway, then you might as well do it since it will be all off anyway.

TGPilot · 07-11-2005

I know it sounds like a total rookie question, but am I right to assume that there are two seperate belts...one for Cam timing, and one for Balance shaft right? What is the recommended supplier for these belts and idler pulleys...Manufacturer (Mitsubishi), aftermarket, NAPA, etc...? I do have full intentions of high HP outputs by late summer.

Thanks for the input guys!!

-Kenny

Matt D. · 07-11-2005

Everyone around here always buys Mitsubishi parts when possible. Might cost a little mor but the quality is better for the most part.

Jakey · 07-11-2005

I have personally seen a balancer shaft bearing fail which resulted in the balancer shaft damaging the block. The block was still fine, mechanically.

**JET** · 07-11-2005

The rear balance shaft runs off the timing belt (attached to the oil pump pulley), the other one runs off a separate belt.

TGPilot · 07-11-2005

I do not spending top dollar for parts...especially critical parts like timing belts and such to handle abuse and give better longevity. YOU GET WHAT YOU PAY FOR...but I want to make sure the quality is there...not just a name.