My wife's 1997 XK8 has developed a strange vibration and noise at 70 mph.
Only on acceleration it sounds like tyre roar but the door mirror glass vibrates alarmingly.
It only happens between 70 and 90 mph on acceleration, as soon as you back of the throttle it stops instsntly.
I have just had all 4 tyres balanced by the company recommended by my usual indy garage and did watch him do it so know it isn't that.
Any suggestions?

Bob

 

If the wheels were balanced on the car, any bearing problems should have been picked up.

Next to check would be driveline:

1. Propshaft / Half Shaft UJ's
2. Jurid Coupling
3. Engine/Gearbox mounts

Graham

 

All sounding expensive as usual!!!

Bob

 

Just because you watched someone balance your wheels doesn't mean they did it correctly and if you just got your wheels done and the vibration just started, you might want to have them force balanced again.

 

+1

............and there's always the chance balance weight(s) haven't been properly attached and dropped off.

Graham

 

If the condition existed before the tyre balance, and it remains unchanged it is unlikely to be the tyre balance.

If it was tyre balance, the vibration would exist whether under acceleration or coasting as long as the vehicle remained in the sensitive speed range.

 

Or if the weights were placed slightly off or if they didn't put the right weight on, the vibration might not manifest until it reaches a specific frequency. The wheel speed between 70 and 90 mph seems to be a somewhat common wheel balance issue for many cars.

 

Again, if it's only under acceleration, wheel balance is not likely cause, whereas drivetrain, mounts are suspect.
RJ________________
97 XK8 Conv. 85K mi

 

This started weeks after a wheel refurb.
I got the wheels balanced to eliminate this or hopefully cure it.
It obviously hasn't cleared it.
It does look like a driveline problem but was asking in case anyone else had experienced this and had a known fault.
I will get to the bottom of it and post the results.

Bob

 

It is all sorted now, couldnt believe what it was till I drove it.

Lambda Sensors!!

CO was up to 9% at 2000 rpm causing a missfire through over fueling.
All changed and CO now back just below 0/5% and no vibration!!!

Bob