250cc_SuperKart

What would cause a motor to vibrate and shake in-between a certain RPM range but then clears up when below or above that range? I have a 1992 Integra and during cold start up's the rev would vibrate and cause a shake inside the car because it's within the 'range of vibration' of the motor..... but when it warms and the idle drops, the motor becomes normal, and if you rev over that RPM vibration range, it clears up and runs smooth.

The range of vibration RPM's from that motor is somewhere between the window of 1,200-2,000 RPM's. I checked to see if it was the motor mount, but they seem to look fine. What could cause this symptom?

Tachi

Engine and trans mounts can "look fine" until you actually extract or remove them and take a close look at all angles. My driver's side engine mount "looked fine" but removing it revealed it to be half torn.

250cc_SuperKart

Yeah, I'm hoping it's just a bad engine mount and not a bigger issue that's gonna cause the motor to go bad.

Do you think it's possible that the flywheel is out of balance or perhaps the crank pulley?

Tachi

The crank pulley is so small and close to the axis it would literally have to be shaped like a crankshaft counterweight to cause that, and it would be at all rpms. I doubt it's the flywheel/clutch assy. My car has always had a cabin vibration from idle up to 2000rpm, and been getting worse over time. I recently installed a new Exedy clutch and FX lightweight flywheel. The PO had installed a cheeBay clutch kit, and with the new clutch the vibrations evaporated.

Anything with the rotating assembly would be most pronounced at lower rpm and smooth out at higher rpm, not occupy a specific rpm range. The B-series engines don't have balance shafts, so its entirely likely that a bad engine mount would allow a harmonic resonance at a specific rpm to propagate and create that vibration.

Lsvtecy0

I had this exact problem where the engine would shake at a certain rpm and would go away as the rpm went higher but this would only happen while I was driving. It turned out to be one of my axles cause they had lost all the grease inside the boot and the joints were seized up real good. Try taking a look at them and see if that could be your problem. GL

baramund

had same problem, had to replace cv joint

Tachi

Well, these engines have 4 mounts supporting the powertrain and two of them are multi-axial mounts so a half tear in a particular direction could do it.