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Uneven idle and low speed acceleration


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Gents

I am lead to believe that a primary part of the problem of low speed uneven running on the late PI 6's is a result of changes made to the inlet manifold.

 

1st is the in-direct butterfly linkage (throttle cable opens 1 & 2, which open 3 & 4, which open 5 & 6); great when new, but when the inevitable wearing takes place in all the linkages, synchronising the the butterflies can be a nightmare

 

2nd is the moving of the idle circuit closer to the cylinder head.

 

I have to say that I am finding obtaining smooth(ish) running on my 1975 model, is proving to be impossible.

 

I have read that it is possible to install the idle screw on my CR in the position as can be found on the CP manifold

It suggests that this;

- Is reasonably simple to do

- Will result in much improved running

- Will mean a reduction in both throttle lag and rough spots

 

Now . . .to my questions;

Is the assertion ref the positioning of idle screw correct?

If so, is it easy and can anyone offer a simple explanation of how it can be done?

 

Many thanks in advance

John

Edited by wjgco
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I think you have a good understanding of the idle and acceleration problem. If the butterflies do not open together you will get hesitant acceleration accompanied by coughing.

 

I have not had to work on a CR for a while but did own one, in fact I cut my teeth on getting it to run properly.

 

So if you say there is wear, and I assume for the purpose of the response you mean on the shaft bushes then start by changing them first. I seem to remember that one of the bushes is a little difficult to change but there are ways and means.

 

Once you have that sorted then the car should run as was intended again assuming all other contributing parts are working as they should. So I would say start with getting the butterflies to open properly and progressively before reaching for the drill.

 

I will look at the brown book for inspiration.

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John

 

My 75 was having the same problem due to very worn throttle bodies (209,000km) - also causing very rich running on 5& 6 as the wave plâtés weren't opening with the others. Change to a better set of refurbed throttle bodies made a huge difference. Still not perfect but no more hesitation. Have ordered new bodies and solid linkages so when they go on it should be better again

 

Graze

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Thanks all

I will contact Neil first, then look at the throttle bodies

I know that there is some wear in the linkages, so, as usual, a number of little things are creating a larger issue

 

The joy of a British classic!

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