Re: [T3] idle problems

[Seldom <seldomss@yahoo.com>]

This afternoon I had time to look at the Fuel
Injection on my '70 Fasty again.  I went over all
manifold connections etc. with a propane torch looking
for vacuum leaks... nothing.  I found the specs. for
resistance between the two outer and two inner pins on
the pressure sensor connector and verified they were
good.  I also found that by cracking the hose
connection running from the manifold to the pressure
sensor just right, the idle smoothes out and jumps
back up to the 1200-1500 rpm range. does this say
something about the condition of the diaphragm?  (I
interpreted it as meaning it's good).  Unbelievably,
the thermostat is there and functioning.  I also took
it out on the highway, hoping to burn off some of the
carbon crud built up from having a faulty voltage
regulator.  Sure is sweet to drive.  

And, following many suggestions, I ordered the Bentley
manual :-) Thanks!  It should be in on Friday.  I
suppose once I receive it I can do a more systematic
check of things but if anyone has any suggestions what
to look at next, I'm all ears.

-Damian

Almost forgot, here's a more complete description of
the cars behavior than in my last post:

>From a cold start the car has a high smooth idle ~
guessing 1200-1500 rpm.  After 2-3 minutes, the idle
drops to ~ 1000 rpm and starts hunting.  Within
another 2-4 minutes, the hunting is severe enough that
it'll stall out.  


Thanks,
-Damian  

--- Jim Adney <jadney@vwtype3.org> wrote:
> On 5 Mar 00, at 21:05, Seldom wrote:
> 
> > The vehicle:
> > 70 Fastback 85K original miles, AT, F/I
> 
> > The status:
> > Replacing the voltage regulator made a huge
> difference
> > with the richness problem so now the car runs well
> > under load, but the hunting remains.
> 
> > The details:
> > - Fuel pressure is at 30 PSI
> > - I've adjusted the throttle valve, and it seems
> to be
> > functioning properly 
> > - resistance for temperature sensor I & II seem to
> be
> > within specs, both when warm and cold
> > - auxiliary air regulator seems to be working OK
> > although there is a very slight vacuum, even when
> the
> > car is fully warmed up. 
> 
> These all sound perfectly normal.
> 
> > - The idle adjustment screw has no apparent affect
> > (vacuum leak I thought!) but
> > - Hoses seem to be in OK shape - I'll replace them
> > next.  In any case, I haven't been able to find
> any
> > obvious vacuum leaks.
> 
> Places to check: intake manifold gaskets, pressure
> sensor 
> diaphram. One way to check is with a propane torch
> (unlit); when 
> the engine sucks in propane instead of air, the
> richness changes 
> and you can note the change in the engine.
> 
> Having changed the VR you should also change the oil
> now, and 
> just getting it running and warm will often have
> good effects. Make 
> sure that the thermostat is connected and operating
> correctly. If 
> the engine can't warm up, it can't burn off all the
> carbon that has 
> accumulated.
>  
> -
> Jim Adney
> jadney@vwtype3.org
> Madison, WI 53711-3054
> 
>
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