Cable tweak = power boost
SOMETIMES the answer to a problem is very simple indeed. I had two vehicles in the workshop within a couple of days of each other. A Defender and a Discovery, both top-notch examples, both fitted with the 300Tdi engine and both feeling a bit sluggish and down on power. They ran well enough but needed a big boot full of throttle to get going and quickly ran out of puff on the long straight that forms part of my usual road test route. The cause in both cases was the same: an incorrectly-adjusted accelerator cable.
The adjustment system on the 300Tdi is common to many other Land Rover products of the same era. The outer sheath of the accelerator cable is formed in a spiral, like the thread of a screw. A knurled plastic wheel is wound onto this spiral, and clips into a large hole in a bracket at the engine end of the cable. By rotating the knurled wheel the tension on the inner cable can be increased or decreased. Over time the adjuster tends to creep along the outer cable, causing the inner to slacken to the point where the throttle arm no longer opens fully.
To obtain the correct adjustment the collar should be screwed towards the end of the cable until the throttle arm just starts to move off its idle stop, then backed off a fraction. Sometimes the adjuster is a loose fit on the cable and refuses to hold its adjustment for any length of time. I
have found that a couple of strategicallyplaced cable ties will stop the adjuster from creeping.
If the throttle arm will not open fully even with the cable adjusted nice and tight, the pedal stop bolt (on Defenders) may require adjustment. This is a long bolt and locknut protruding from the back of the accelerator pedal, and should be adjusted until it contacts the vertical face of the pedal bracket with the throttle arm fully open. While we are on this subject, a word of warning: that projecting bolt has a nasty habit of snagging on aftermarket floor mats and carpets, jamming the throttle wide open. A few weeks ago I had a Defender in for a tune-up. It had a 3.9-litre V8 engine, Edelbrock four barrel carburettor and various other goodies, and had just come back from an interior retrim.
I rounded the bend onto the long straight, floored the throttle in third and the old beast took off like an antelope pursued by hungry lions. At around 4000 rpm I went to change to fourth gear and discovered that the accelerator pedal was firmly stuck to the floor. In this kind of situation it is easy to panic. Luckily I had the presence of mind to kill the ignition instead and the Defender coasted to a halt in a farm gateway. I pulled the new carpet out of the driver’s side footwell, threw it into the back of the vehicle and completed the road test in a rather more sober frame of mind.