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Re: [T3] 72 square, rough idle, #1 missing?

On 6 Mar 2002, at 19:47, vw_type3 wrote:

> Yes I have the Bently manual. My dist only has one hose on the diaphragm.
> Only one spot for a hose.

Okay, then you no longer have the 72 setup and you don't have a vac retard 
at all. The single hose is a vac advance. You should time your car as if it 
were a 73. You will never measure any vacuum in that hose while your car is 
standing still; it only gets vacuum when up to speed and cruising.

> No diagram in the Bently unfortunately that I have found. what I have is the
> following. There is a small (approx 1/4") port on the aid distribution box just
> in front of the throttle butterfly centerline. A line is connected to that which
> heads toward the dist. Near the dist there is a "tee" one port of the "tee"
> connects to the line from the air distribution box. One line connects to the
> dist and the last goes to the deceleration mixture control valve. According to
> the bently manual and its decription of the valve on "fuel system" page 26 this
> valve was installed on california cars only. Having just read the manual on this
> valve I need to test it as well, but apparently its function is only during
> decel. I am guessing here, but it looks like it might be to supply a little
> extra air to the air intake only when the throttle closes from a high RPM, and
> at the same time retard the dist.

The vac advance line used to connect thru a valve next to the pressure 
sensor (on the left of the engine.) This allowed vac adv only in 4th gear. In 
order for this to work the valve still has to work, the switch on the tranny has 
to work, and all the wiring in between also has to still be there and 
connected up right. There should be NO Tee. I strongly recommend that you 
just connect this vacuum line straight from the dist to the intake air 
distributor, no valve, no Tee. You should test the vac adv by sucking on that 
hose while the engine is idling: The can should hold vacuum and the idle 
speed should increase.

> Yeah that was my bad, I have injector plugs #3 and #4 crossed. I dont think its
> possible for no injectors to fire, at least in my car. The injector point
> connection to teh dist does not even have to be connected for the injectors to
> fire when opening the throttle, they just fire according to the way the
> flip-flop was last set. That of course may be different in differnt models

I've never been able to see much difference with the crossed wires. I think it 
may make a small difference at idle with a cold engine. Once you're driving, 
the extra time that the little bit of fuel spends outside the intake valve is 
probably just spent evaporating and cooling the intake valve.

That's an interesting possibility. That's pretty much the way that I thought it 
worked, but someone else here a year ago had a ECU that worked 
differently. I haven't actually looked for this on any of my cars. Like you say, 
this could be different for different models, or there might be a moment when 
both contacts are closed, which might inhibit everything.

> > Did the resistance come down to near zero (less than 5 Ohms?)
> Definitely down to .3 if I remember correctly

That's clearly fine.

> > The spark and compression tests are the right next steps. You have normal gap
> > (.027-.028") on the SPs?
> I am glad you mentioned this....the bently manual states .024 as does a
> haynes manual. The owners manual states .028 why the difference?

I don't know. I'd never noticed this disparity. I just know that if you open them 
up to .036-.040 as some electronic systems request, the spark will tend to 
jump over at other places, so this is usually a bad thing to do.

Note my comment in another message about the loose injector wires. This is 
a common problem because it appears that Bosch changed the thickness of 
the metal they used in the male pins in the injectors themselves. I often find 
that new injectors don't make good contact, while old ones do.

It sounds like you are electronically adept, so you should be able to figure 
out how to get the harness connectors apart and very gently squeeze the 
female connectors down slightly. Check their fit on the injectors themselves 
once you get the female pins out of the plastic bodies. The should require 
some small force to install and remove, but I often find that they are 
completely loose (on replacement injectors.)

Jim Adney
Madison, WI 53711-3054

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