[T3] Irregular Idle....again...

[Jim Adney]

On 11 Nov 2012 at 11:53, J. Jonik wrote:

> ----  No, when putting 73 engine into the 71, I did not bring along the 
> pressure sensor or brain box because, basically, all I changed was the 
> engine block.  All the other components...injectors, generator, temp 
> sensor, coil, AAR, TVS, distributor, were just what was in the 71 to 
> begin with.  Engine sounds like it's running great...except for this 
> idle thing.  Except when revved, it jerks when driving...kinda as if I 
> was towing a trailer.

How about the intake air distributor and the breather box? Do you 
have the '73 of both or the '71 of both, or are they mixed? They 
won't do well if mixed.

I've had a lot of trouble with '71s when driving at low speeds and 
very light throttle. They seem to jerk back and forth under just the 
right conditions. I don't have any good solution for this, but 
anything that reduces backlash in the drive train helps. If your CV 
joints are loose, that will make this worse.

> ---  The clamps on those fat manifold hoses
>  are not centered over where the pipes meet. They are off to the side a 
> bit, towards the air distributor....which a T-III mechanic advised a 
> good while ago.    So, the hoses allow for any slight movement.  I 
> wasn't aware that movement was the reason to not center the clamps. Good
>  to know.

When reassembling the engine, the hoses should be slipped all the way 
onto the intake air runners. Then the ends of the IAD and air runner 
pipes should be lined up as well as possible THEN their mounting 
bolts for all 3 tightened. Then the air runner pipes should be bent 
to make the alignment perfect (they bend fairly easily.) Only then 
should the hoses be slid onto the IAD stubs.  

If this is done carefully, no clamps will be necessary. If you have 
an engine that has been assembled carelessly, your hoses will have an 
offset to them that will make them seal poorly. If this is the case, 
you can replace the hoses, or use hose clamps until the hoses 
straighten out.

If I'm rebuilding an engine, I slide the hoses onto the air runner 
pipes while everything's apart. This tends to straighten them out so 
they fit right when everything goes back together.

-- 
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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