HERE IS THE PROBLEM:



95 NA with 59k miles....At 5000 rpm to redline I get a very fast frequency vibration in the engine. It can be heard like a howl. Felt in the shifter and clutch peddled ..and the entire car, Feels like my sonic care tooth brush. Accelerating hard to say 6000rpm vibration is strong then letting off the gas she really grinds and howls. Pushing in the clutch the vibration can no longer be felt in the shifter nor clutch peddle. But remains buzzing in noise and seat of the pants. This does it based on cars consistent RPM in all gears, not tires or driveshaft. Problem is long term/chronic issue. Gas mileage is very poor.



T-belt, and clutch with flywheel resurfaced made no difference. The vibration is so bad it feels like it is robbing power from engine. Car runs great and pretty smooth below 4500. What is out of round? Car is stock everything except K&N air cleaner.

Here is what we did Sunday: (NONE had Impact to isolating the Vibration.)
1. Removed Fan.
2. Removed AC Pully/AC belt
3. Did stethoscope checks Could not find a louder spot.
4. Harmonic Balancer seems smooth and solid
5. Turned VTC on by Grounding and Turned Off by unplugging...(Either way didn’t seem to do change how it drove much to performance? (Only did short 2 blocks wo fan)).
6. Put Jack under Trans to check Motors Mounts...was a bit less noise but still vibration!

A few more clues:
1. I removed the top Cam Gear Covers and No belt dust...Belt looks new – 8K on it. We Have not checked Tensioner/other T-Belt pulleys yet.
2. With all the revup test...Vibration starts at 5000 and PEAKS at 5800 RPM. When you let it slow down vibration stops at 4800 RPM....(This whole CYCLE is very consistent)
3. Pushing Clutch in and out changes the noise a bit Less when in...but Vibration continues. When Clutch is IN...the peddle has less vibration as does shifter.
4. Vibration occurs in neutral and all gears.
5. Exhaust system seems solid. But has a few dents.
6. Car has 59K on it!
7. Car gets poor gas mileage and is about 15-20% weak on power... MY 1990 blows this 1995 away.
8. I have owned car 10 years and I think it has always vibrated pre and post clutch work. I THINK.

MY GUESSES:
1. Flywheel/Pressure Plate? (They were replaced about 6 years/5000 miles ago.)
2. T-Belt Tensioner
3. Does car have Engine Balancer...? Runs of T-Belt?
4. Bad engine internal bearing/Balancer?

HELP Anybody have any ideas? Experienced this issue?