Re: Cheap multimeter & adjusting mixture

[Orin Eman <orin@WOLFENET.com>]

> frequency valve duty cycle - that's what I bought this meter for. Set
> for 4 cylinders the dwell oscillated between 28 and 37 degrees, which
> (as I understand) means 33/90 = about 37% duty cycle. With the dipstick
> removed the average dwell was about 45 degrees, which equals to 50% duty
> cycle. Because the duty cycle increased as I removed the dipstick, I
> assume I was measuring the "true", not "reversed" duty cycle - the more
> the frequency valve works, the richer the mixture is, right? So with the
> 37% duty cycle with the dipstick installed, I'm running too lean. Of

Nope, your basic setting is _rich_ and the computer is leaning the
mixture.  When you pull the dipstick, the mixture goes leaner and
the computer increases the duty cycle to compensate.

You could reset to factory specs of 50%/45deg, but for best
performance, you should set it around 38 degrees average.

> course, every now and then I _have_ to reveal my stupidity, so in search
> for the mixture adjustment screw I figured out (don't know how, don't
> ask, I was hungry and tired) that I have to remove the yellow plug at
> the intake boot. After getting yet more tired, bitching about how
> stupidly German cars are build, almost tearing the whole injection assy
> out of the car, breaking the plug and extracting the remains with
> various tools, I figured out I removed and destroyed an innocent plug
> that wasn't meant to be removed. I substituted the plug with a bolt
> wrapped with electrical tape, praising the Lord I didn't break anything

Yes, it _was_ an innocent plug.  Sounds like it's a dead plug now.

> expensive. I finally found the adjustment screw (or I think I have), so
> I probably will attempt to adjust the mixture and idle speed. I would be
> grateful for any hints - my previous post on this subject didn't catch
> much attention... :-( My idle and WOT switches do work and the temp
> sensor is within spec, yet the cars idles at 1100rpm when hot. What's
> up?

The mixture screw is down between the intake boot and fuel distributor.
There is _supposed_ to be a metal plug sealing the hole (the hole is
5mm or so), but in the US, I've never seen one.  You need a long
3mm allen wrench to reach thru the hole down to the screw.
You want to make very tiny adjustments to this... turn the screw
just a few degrees at a time.

As for the high idle, does your car have AC?  If it thinks AC is on,
it will idle high.  Is the O-ring around the idle screw intact?

Orin.