Engine vibration '78
 

Hi all

When I rev my engine ('78 4.5 Cis) to almost excactly 2500 rpm, a strong vibration occurs.

2400 is fine, so is 2600. Also there when engine braking. It is most noticeable in 5th gear, since the revs are in the troublesome area for longer, but it's there in all gears including neutral.

Has always been a problem, never goes away, but is lesser when the engine is cold. Put some injection cleaner in the tank and it did help a little.

Shine your wisdom upon my car, ye oracles!

Motor mounts?

motor mounts are solid, but there still may be something going on there. Get the car in the air and see what is happening through the rev range. You could also be feeling a torque tube bearing starting to spin out.

Yeah, I had an early car with the solid mounts and they had both failed, pulled apart where the metal joins the rubber. That allowed the engine to do some fairly strange things....like vibrate at certain rpm's.....

I doubt it is the mounts. I've had one with bad mounts and it was not the same sensation. Feels more like the engine struggles or misfires. Also doesn't pull as hard. Checked again yesterday and it's more like between 2300 and 2500 rpm.

But then again, timing or misfiring doesn't explain why it vibrates when lifting off.