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Throttle cable

Neil Potter

800 views

22 February 2014

Since putting the carbs back I've suffered from a sticky throttle cable, which, whilst not affecting driving much, did make the idle too high and unpredictable.

The cable on this car, and presumably all earlier models, is a bit odd to my eyes. Unlike the later cables routed around the engine where the inner cable actually pulls on the throttle arm through the intake manifold from the top, this cable runs up from below, between the carbs, and has the inner cable fixed on to the cam cover. The act of pushing the pedal effectively straightens the outer cable, and it is this action which pushes on the throttle. Took me a while to make sense of inner cable movement at one end but none at the other.

The problem was that the outer cable had split and corroded about midway between where it emerges into the engine bay and terminates at the throttle arm. Disconnecting it over the carb refurb had probably disturbed some rust, which was now causing the stickiness. Nothing for it but to replace the whole cable rather than get away with threading a new inner through from the footwell.

As it happens, when I replaced the carpets last year I expected to have to replace the cable, as the end of the inner in the engine bay was looking very frayed. I bought a new cable, and having found the grommet behind the map pocket managed to get it into position. But I couldn't work out how the cable got down to the footwell, as the existing cable seemed to disappear into the transmission tunnel. Rather than take apart even more of the interior at a time I was feeling pretty fed up with the job, I left the new cable partly fitted. MISTAKE! I'd have saved a lot of effort by persevering.

It seems that Lotus started with the chassis and the throttle cable, then built the rest of the car around it.

What I did
The cable runs under the soundproofing foam along the RHS of the transmission tunnel down to a clamp which holds the outer cable in place against the transmission tunnel while the inner cable goes on to the pedal. The inner sits in a pivot which fits on to the pedal arm, which is held on to the arm but free to pivot with a nasty piece of bent wire acting as a cotter pin holding the pivot in place. This is very hard to access to remove, as it's right up against the tunnel wall. You can't get a Dremel to it unfortunately, so I can only advise that you persevere with long-nosed pliers. You'll need to improvise something as a replacement - I used flower arranging wire bent into an S shape using mine own hands and a metal thimble.

To get access, I removed:

-Map pocket
-Drivers seat
-Steering wheel
-Top transmission tunnel trim panel
-Two bolts from the LHS of the binnacle, and loosened the others, in order to lift it so as to remove...
-The trim panel around the stereo/HVAC
-The RHS tunnel trim

Then I needed to peel back some carpet and cut into the soundproofing foam to get to the cable.

The last sting in the tail was threading the engine bay end through the plastic sheath which sits in the throttle arm. Hard to do as you can't really see it, so I had the future Mrs P act as eyes as I tried to do it. I was terrified I would knock the sheath out of the arm and have it disappear somewhere. In hindsight I should just have removed the sheath and put it onto the cable before trying to get it in position, but then you have the long throttle return spring (attached to the throttle arm) free to get in the way...

You might need to cut back the outer cable in order to have enough inner cable to run between the anchor point on the cam cover and the throttle arm. Then, once installed, use a helper to check you are getting full throttle and the pedal stop is acting at that point.

All in all, a tedious and awkward job, where everything seems to get a lot worse before it gets better. So par for the course when working on the Esprit then! Probably took 4 hours.

Results
Having done this job, the results do make it worthwhile. In hindsight, the throttle had probably been a little sticky for some time, and now the car revs freely and under control. The slightest movement triggers a response, and the car feels MUCH more willing and twitchy - more like it should I think.

Another tick on the list!

Other notes
The cable I fitted was a Lotus part, with a mild steel cable. On reflection you could easily make up a stainless cable with a Teflon coated outer which would be higher quality, you'd just need the stainless cable to have a nipple at one end to fit in a suitable pivot. I made up my own stainless cable for the choke cable, and was very happy with the result. That said, the first throttle cable did last 26 years so it did a decent job...


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Great guide Neil! I expect I'll have to go through this in a few weeks as my throttle cable is extremely sticky as well (I lubed it with Gearbox oil...worked great for a week, then became treacle...) - my cable goes through a transparent tube into the transmission tunnel and then down to the pedal though. 

 

I'm hoping that by undoing the clamp near the footwell it'll just slide out easily through that tube. But knowing Lotus there are probably other hidden horrors waiting for me :) 

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Thanks Vanya.  You'll be pleased when you've done the job, and that plastic tube makes sense - you probably won't be wrestling with the soundproofing at least.  Good luck!

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