'87 Jetta GLI 16V - progress

OK guys, here's where I'm at now with this (formerly) dead VW:

After going through everything from air cleaner to intake, repairing
what little I could find wrong, replacing all suspect vac hoses, and
fixing one vacuum leak, I got it where I could drive it - barely. It's
obviously running way lean, because once I get the throttle into the WOT
enrichment, it wakes up immediately.
I know the rice-rocket shop turned the fuel distributor adjustment
screw a bunch, not knowing what they were doing. My question is, does
that have an effect on the basic running mixture (as opposed to idle
only)? Can I expect to crank the 3mm adjustment screw a little at a
time and bring the mixture into a drivable range?
I know the correct way to do this is with an ammeter reading the o2
sensor circuit, but the o2 sensor does not get hot enough to operate for
this purpose. Remember this is a race car, and most people racing these
effectively bypass the o2 sensor and treat it as a straight CIS system.
--
- -
Rex Burkheimer
WM Automotive
Fort Worth TX

Try turning the CO adjustment screw for best idle and see what that does.
Then turning that screw out (CCW) should lean the CO and the engine should
become more responsive.
Adjusting that screw should have an effect on off-idle response too AFAIK.

Do you have a CO analyzer at your shop?
Do you analyzer how rich the engine is running by examining the spark plugs
at different times, like after a WOT run then turning the engine off to see
what color the spark plug tips are, or after a cruise down the expressway,
etc.?

You can, or should be able to, hook your VOM in series up to the Fuel
Pressure Regulator to read it's voltage.

Good luck,
dave
(One out of many daves)


"Rex B" > wrote in message
...
> OK guys, here's where I'm at now with this (formerly) dead VW:
>
> After going through everything from air cleaner to intake, repairing what
> little I could find wrong, replacing all suspect vac hoses, and fixing one
> vacuum leak, I got it where I could drive it - barely. It's obviously
> running way lean, because once I get the throttle into the WOT enrichment,
> it wakes up immediately.
> I know the rice-rocket shop turned the fuel distributor adjustment
> screw a bunch, not knowing what they were doing. My question is, does that
> have an effect on the basic running mixture (as opposed to idle only)?
> Can I expect to crank the 3mm adjustment screw a little at a time and
> bring the mixture into a drivable range?
> I know the correct way to do this is with an ammeter reading the o2
> sensor circuit, but the o2 sensor does not get hot enough to operate for
> this purpose. Remember this is a race car, and most people racing these
> effectively bypass the o2 sensor and treat it as a straight CIS system.
> --
> - -
> Rex Burkheimer
> WM Automotive
> Fort Worth TX

dave wrote:
> Try turning the CO adjustment screw for best idle and see what that does.
> Then turning that screw out (CCW) should lean the CO and the engine should
> become more responsive.
> Adjusting that screw should have an effect on off-idle response too AFAIK.

This is the 3mm screw below the hole by the fuel distributor, right?
So screwing it in (CW) should richen the mixture?

> Do you have a CO analyzer at your shop?

No.

> Do you analyzer how rich the engine is running by examining the spark plugs
> at different times, like after a WOT run then turning the engine off to see
> what color the spark plug tips are, or after a cruise down the expressway,
> etc.?

I do read the plugs occasionally, but it hasn't run well enough so far.
I'm in the "rough" tuning stage now.

> You can, or should be able to, hook your VOM in series up to the Fuel
> Pressure Regulator to read it's voltage.

I was told by a VW tech that the O2 sensor wasn't getting hot enough to
do that, due to a convertor whose guts were gone. O2 sensor is in the
cat convertor shell, shielded from direct exhaust flow. So I haven't
done that.

>
>
> "Rex B" > wrote in message
> ...
>
>>OK guys, here's where I'm at now with this (formerly) dead VW:
>>
>>After going through everything from air cleaner to intake, repairing what
>>little I could find wrong, replacing all suspect vac hoses, and fixing one
>>vacuum leak, I got it where I could drive it - barely. It's obviously
>>running way lean, because once I get the throttle into the WOT enrichment,
>>it wakes up immediately.
>> I know the rice-rocket shop turned the fuel distributor adjustment
>>screw a bunch, not knowing what they were doing. My question is, does that
>>have an effect on the basic running mixture (as opposed to idle only)?
>>Can I expect to crank the 3mm adjustment screw a little at a time and
>>bring the mixture into a drivable range?
>> I know the correct way to do this is with an ammeter reading the o2
>>sensor circuit, but the o2 sensor does not get hot enough to operate for
>>this purpose. Remember this is a race car, and most people racing these
>>effectively bypass the o2 sensor and treat it as a straight CIS system.
>>--
>>- -
>>Rex Burkheimer
>>WM Automotive
>>Fort Worth TX
>
>
>

"Rex B" > wrote in message
...
> dave wrote:
> > Try turning the CO adjustment screw for best idle and see what that
does.
> > Then turning that screw out (CCW) should lean the CO and the engine
should
> > become more responsive.
> > Adjusting that screw should have an effect on off-idle response too
AFAIK.
>
> This is the 3mm screw below the hole by the fuel distributor, right?
> So screwing it in (CW) should richen the mixture?

It should.

> > You can, or should be able to, hook your VOM in series up to the Fuel
> > Pressure Regulator to read it's voltage.
>
> I was told by a VW tech that the O2 sensor wasn't getting hot enough to
> do that, due to a convertor whose guts were gone. O2 sensor is in the
> cat convertor shell, shielded from direct exhaust flow. So I haven't
> done that.

Your 02 sensor should be a heated one and come online within a few minutes
of the engine running.
Also I like to check the FPR voltage to make sure that there is some and
also that it changes.

> Your 02 sensor should be a heated one and come online within a few minutes
> of the engine running.

So the internal heater should be able to get the sensor into the working
range, without benefit of a blast of exhaust heat?

> Also I like to check the FPR voltage to make sure that there is some and
> also that it changes.

Is that a standard test? That's the rectangular box on the side of the
FD, correct?

Rex

"Rex B" > wrote in message
...
>> Your 02 sensor should be a heated one and come online within a few
>> minutes
>> of the engine running.
>
> So the internal heater should be able to get the sensor into the working
> range, without benefit of a blast of exhaust heat?

yes at least initially, but exhaust should be hitting even with a gutted
cat.
I am not totally sure on this since I only deal with 'working' & complete
cats. <g>

>
>> Also I like to check the FPR voltage to make sure that there is some and
>> also that it changes.
>
> Is that a standard test? That's the rectangular box on the side of the
> FD, correct?

Should be in the Bentley.

I adjusted the mixture screw last night until I could blip the throttle
without it trying to die. Then I drove it around the neighborhood a bit,
and it seemed to drive pretty well, although it was not perfect. Once it
got over about 5000 at WOT it really came alive, something it has not
done well since I've owned it. It may be still too lean, and it has
that odd smell that I used to associate with incorrect ignition timing.
Additional tuning is indicated, but I am going to try and leave that
for the next owner. Thanks much to Dave and others for your help.
- -
Rex Burkheimer
WM Automotive
Fort Worth TX

Rex B wrote:
> OK guys, here's where I'm at now with this (formerly) dead VW:
>
> After going through everything from air cleaner to intake, repairing
> what little I could find wrong, replacing all suspect vac hoses, and
> fixing one vacuum leak, I got it where I could drive it - barely. It's
> obviously running way lean, because once I get the throttle into the WOT
> enrichment, it wakes up immediately.
> I know the rice-rocket shop turned the fuel distributor adjustment
> screw a bunch, not knowing what they were doing. My question is, does
> that have an effect on the basic running mixture (as opposed to idle
> only)? Can I expect to crank the 3mm adjustment screw a little at a
> time and bring the mixture into a drivable range?
> I know the correct way to do this is with an ammeter reading the o2
> sensor circuit, but the o2 sensor does not get hot enough to operate for
> this purpose. Remember this is a race car, and most people racing these
> effectively bypass the o2 sensor and treat it as a straight CIS system.