General: 850: Clutch judder cured with a few drops of oil

[Moose850]

The title may be slightly misleading but let me explain.
I bought the car just over 10 years ago and it had a weeping rear main seal. I replace the seal and at the same time fitted a new clutch. The car had suffered from nasty clutch judder since I had it and I expected the new clutch would resolve this. When replacing the clutch I checked the flywheel for ‘run out’ and it was fine.

After the new clutch was fitted the judder was still there and has been for the last ten years. It juddered on take-up of drive just as the clutch was biting, once fully engage the judder stopped as you would expect. Most of the time you accepted the judder and got the clutch engaged as quickly as you could, other times it was too bad and you had to dip the clutch to stop the judder and go again. It became an automatically applied technique.

All engine mounts were checked and serviceable.
Another thing I noticed when I got the car was that the throttle felt as though it had a strong return spring, stronger than normal. Another Volvo 850 owner said this was normal and stupidly I believed them and accepted it – for 10 years.
A few weeks ago I was having a general look around the engine bay when I thought I might try lubricating the throttle mechanism to try and improve the pedal. I gave the throttle damper a twist to check the ball joints on each end it was a stiff as hell. I removed it and cleaned the ball sockets then cleaned up the ball ends on the linkage, lubed both and refitted. For good measure I dripped some oil onto the spring (see pics) on the lever that is fixed to the throttle body in the hope that it would drip through the coils and into the shaft. I also did the same to the sprung bobbin that the throttle cable coils around.

I drove the car afterwards expecting perhaps to feel some sort of improvement on the feel of the throttle pedal and there was, it felt light as I always thought it should but to my amazement the clutch judder had almost totally gone. On a 30 mile drive I felt the slightest judder on a few occasions but it came to nothing.

Obviously there was never anything wrong with the clutch. This is my theory…..
The throttle mechanism was partially seized so when operated, although not detectable by the driver, it was ‘notching’ not moving smoothly. The TPS detected this but the delay in engine response meant it got into a quick oscillation of ‘throttle on’ to ‘throttle off’ which could only be broken with either a large throttle change or full engagement or disengagement of the clutch.
I suspect the tiny bit of judder I get on the odd occasion now could be due to a throttle body that requires cleaning or adjusting very slightly.

It would be interesting to know the thoughts about this from those out there that know way more than me about the Volvo 850 throttle system. Either way I am very happy now but wish I had done it 10 years ago.

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