[T3] Weird Idle Problem

[Jim Adney]

On 2 Jul 2012 at 13:45, Toadpipe wrote:

> Lately my idle has started being really high, high enough to make my 69 
> Square (D-Jet) do the the revving dip thing when it's cold.  Strange 
> part, the idle adjust screw is all the way down, it should be idling so 
> low that it stalls.  Ideas?

You're getting extra air in at idle for some reason. You just have to 
find where the excess air is getting in.

Make sure the throttle cable isn't sticking, keeping the throttle 
valve from closing all the way.

Make sure the pressure sensor hose hasn't fallen off the underside of 
the IAD.

As Dave mentioned, make sure the AAR is closing, since they often 
start to bind up by this age. Test it by closing off its intake hose 
to see if this stops the loping when the engine is warm. If it does, 
I can usually fix the AAR. It's a pretty cheap repair.

If that doesn't do it, I'd slide the 4 large hoses back from the IAD, 
then examine how the intake air runners line up with the IAD pipes. 
If they are bad, you should loosen all the nuts that secure all 3 
parts and retighten them, aligned as best possible. If you don't have 
the right FI (only) 3/16" phenolic insulators at the heads, these 
will never be right.  

Once you get these parts aligned as well as possible, you may need to 
bend individual intake air runners to get them to align perfectly. 
They bend fairly easily.

Then slide the 4 large hoses back over the junctions. If the hoses 
have developed an "offset" from mis-aligned pipes, you may need to 
hose clamp them for a season or so to get them straight again, but 
take the hose clamps off eventually so things can slide as the engine 
expands and contracts with temperature.

Getting the pipes aligned after someone has rebuilt the engine and 
ignored it takes a lot of time and isn't easy. It's a LOT easier to 
do this right as the engine is going together.

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