Hello, I have a 1998 Jaguar XK8, and there is a problem with it. When I press a throttle pedal for a certain distance, really strong vibration occurs, the car is shaking. For example, when the road is flat, vibration will start from, approximately, 100km/h. And when I go uphill — from 70-80km/h. When I go downhill, my speed is 100km/h +, and I don't press throttle - there will be no vibration. What could it be?

 

Watch the engine running with the bonnet open. Rev it up to around 3000 rpm in neutral. See if you can see/hear/feel anything. If not, put it into drive, hold the brakes on and blip the throttle again. See what happens now.

Report back on what you see after these test but my money is on a failed engine mount which will be obvious as the engine will cant over as the throttle is applied. You might even be able to move the engine from side to side by hand.

Richard

 

Thank you for this response. I think, I will be able to check it on wednesday/thursday, and will report about the results

 

cracked flex plate maybe?

 

My first thought was maybe a U-joint? in either event, I would put it on a lift & check everything for any looseness.

 

Maybe... I thought about torque converter, went to check gearbox. They diagnosed it with a computer, said everything is fine with the gearbox, but I had to change lambda sensor. I did it and nothing has changed.
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Could be, sometimes there is a strange sound, when I change gear from reverse to drive

 

If none of the above, may be failing ignition coil(s) - causing misfires and that's what you feel.

 

I have found out what causes this issue. When I bought this car, the LPG system has already been installed. And yesterday, when I changed mode from LPG to gasoline - the problem disappeared. As I understand, LPG filters must be changed and then the car should work fine in both modes.