Jump to content
Click here if you are having website access problems ×

Lumpy throttle cable


Recommended Posts


I have noticed over the last few drives that the throttle pedal isn't very smooth on my 620S, which makes it tricky in traffic pulling away smoothly.

I just disconnected the end of the cable and in isolation every part seems to move freely; the pedal, the cable and the thing on the engine end, they all move OK.  But when I put it together, it is overly stiff, as if the cable is rubbing somewhere.  Having listened carefully, the only sound which suggests friction, is at the engine end, and if I disconnect the pedal end it is still a bit jerky, which makes me think it is the engine end, where the wire inner cable comes out of the outer part.

I considered a bit of lubrication, but my feeling is that it shouldn't rub in the first place, so this may not help and shouldn't really be needed.  Or should I just put some 3-in-1 down the cable and hope for the best?

My second question, is how do you get to it, as it is well and truly trapped below the inlet manifold above and supercharger pipework below! I can just about get a finger or two to it from the sides and there seems to be a black, square nut on it (see pic below, taken through the inlet manifold), but I can't seem to move it and don't know how it all goes together.

Any help and advice would be much appreciated?

P.s. I should add, the car is only 3 years old, so there are no signs of fraying or corrosion, every part still looks like new.



Link to comment
Share on other sites

Mine went stiff after a track day, with the same diagnosis as you. Think my cable was old stock so the lube was dry.

I bought a cable lubricator tool and some chain lube which forces the lube down the cable. It worked a treat and it has been lovely and light since. 

Link to comment
Share on other sites

Is the cable close to the Exhaust headers? 

On my 420 the cable was routed quite close to the headers and it melted the rubber into the inner cable and made the throttle sticky and not smooth.

Had to replace and reroute the cable higher up and used some heat shield sleeving.


Link to comment
Share on other sites

One of these you mean?


You say you used chain lube, but the chain wax I have doesn't have the straw to connect to the nozzle and as I understand it the above tool only works if the can has the straw nozzle? The only thing I have with a straw that is close is the ubiquitous WD40, which I guess will do the job, but might not last as long as a heavier chain lube?

Fortunately, on the 620S the routing of the cable is around the back and down the 'cold' side of the engine, so although I'm sure it gets hot, it shouldn't be anything like exhaust manifold hot.

Link to comment
Share on other sites

  • 1 month later...

Just wanted to follow up with this... I squirted some normal WD40 in by hand and that improved things, but I was concerned it would quickly evaporate or burn off.

So I got some of this for £7:


And one of these for £8:


My first problem is that on my 620S the top (pedal) end of the cable has a plastic thingie attached for it to clip on to the pedal box hole.  It seems odd that the plastic thing is fixed to the cable; there is no reason why it needs to be fixed on and it would make the cable very car-specific, but pull as I might it won't come off!  This means you can't get the above tool clipped on to it!!! *ranting*

As mentioned above, I can't work out how to liberate the bottom end of the cable from behind the inlet manifold.  But in the end I worked out I could just about get the above tool clamped on to the bottom end of the cable with the cable in situ, using feel alone, and then pass the tube of the spray grease between the inlet pipes and get it all plumbed in.  A few squirts later, with plenty of rag held around to catch overspill, and I have a properly lubricated cable, with grease coming out of the top end, which must mean it is spread throughout the whole cable.

Anyway, hope that helps someone sometime...

Link to comment
Share on other sites

Lube may well help, but, a properly made cable will have a Teflon liner and not need lubrication.  If it needs lubrication, this means it's time for a replacement and it will be toast soon. The motoring gods are sending you portends now so you don't end up shipwrecked later.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...