Diagnose This: Episode 2 - a tribute to Cathy (very long)

[scirocco at vintagewatercooleds.com (Eric S)]

Ok, here is a reminder, see under the quote for changes/current state, and
a "Boykoish" story of CIS woes.

Eric S said:
>
> On this episode of Diagnose This we bring to you one sluggish VW Fox.
>
> Patient details:
>
> 1990 VW Fox Wagon
> 1.6 liter, Heron Head 8v, 9.5:1 compression
> Stock CIS-E
> Stock Exhaust
> Iginition timing at 8 degrees
> Cam timing advanced 1 tooth, this rasied our compression to 160 psi a cyl!
>
> Symptoms:
>
> 1. Slow to rev even just idling and bliping the throttle
> 2. Super slow, can barley maintain 80 mph, making maybe 60-70 hp on the
> butt dyno
> 3. Runs excellent, idle smooth, a soft miss when under load, more of a
> surging really
> 4. Plugs show proper mixture, O2 system not having to do any adjustments,
> and confirmed its operating correctly (ground the O2 wire, it idles up,
> then loads up and starts to falter, give it 12vs it dies, no change in
> idle speed with O2 unhooked or hooked)
> 5. Car just feels like it can't breath, similar to how the previous 1.8
> acted, but now much more pronounced with the 1.6
>
> Possible causes (feel free to add on here and "vote" for your diagnosis):
>
> 1. Cam timing? I am already 1 tooth advanced, this got me to the proper
> comression
>
> 2. Cat clogged? This could explain why I hated the 1.8 so much, and the
> sluggishness to rev
>
> 3. Intake/Injection issues?  Fox intake is one of the best flowing from
> what I have heard?  Its all the stock Fox CIS-E stuff, just with the
> shrouds knocked off the injectors.   Cannot check DPR current (don't have
> the harness).


OK, so, here is what has been done/discovered:

Thanks to Timbo, he reminded me of the retarded restrictor just before the
cat that VWoA installed.  That has been removed and the cat um...de-catted
we shall say (mmmm, platinum dust, cough cough).  This brought some
improvement in driveability/power.

Next, my mechanic told be of a restrictive screen in the main fuel inlet
banjo bolt on the Fox CIS-E distributor.  Damn right its rescritive,
removed that banjo bolt and replaced it with a normal one without screen
from CIS-E-Motronic.  This made the car more rev happy and peppy for sure.
 So...still think something is wrong with fuel.

Cue Cathy drama:

I decide to do the spray pattern test as well as volume test on the
injectors.  Spray pattern is crap on #3, and it flows a full %25 percent
less at full spray than the other 3...the other 3 injectors have not the
greatest spray patterns, but ok anyway.

So I swap #3 and #4 injector (sound familiar yet Cathy?) and guess what,
crappy spray pattern follows the injector, but the low flow sticks with
the #3 spot, lovely.  So, clogged line or bad fuel dist are my only
choices.

Hmmm, I have no spare Fox CIS-E fuel dists now do I?  Nope, a friend had a
set of injectors that we managed to find a good one, so solved the spray
pattern issue....but what to do with the low flow on #3?

Oh, ok, its time to get experimental!  So, I have this spare
CIS-E-Motronic dist from my old 2.0 16v Caddy....hmmm, part numbers are
different, but what the hell, lets give it a shot.  Bolt the spare dist on
to the fox air flow plate....wierd, injectors spray even with plate all
the way down, BUT the injectors all flow within 1% of each other now (and
quite a bit more volume too!!!).   So, we adjust the Fox air flow plate
all the way down, injectors STILL spray when plate at bottom...thats no
good.  Time to inspect the fuel dists and air flow plate differences. 
Sure enough, the piston on the CIS-E-M dist has a good 1/2 inch more
movement in it than the Fox CIS-E one...and you can visually see the
differences in the pivot points of the air flow plates between the two. 
Ok, so I rip the whole fuel dist and air flow plate out and put the
CIS-E-M dist back on its plate and re-install.

Moment of truth, test the injectors and flow one last time, all looks
good.  Pop the injectors in, and fire her up.  WOOT!  Fires instantly,
smells way rich, lol.  Lean it out a bit, idles beautiful, smooth, no more
missing.  But it wont rev at ALL, just bogs if you give it ANY gas.  Shit
I think, this won't work, I'm gonna have to put the fubared Fox dist back
in.  Oh wait, KNUCKLEHEAD!  Helps if you remember to plug the DPR back
in...LOLOL.

Plug it in, and REV BABY!  Oh, you can hear the difference just revving it
at idle...no more boggishness and slow to rev, it SNAPS to life with just
a little twist of the throttle!  NICE!  Still wierds me out to have some
frankenstein fuel dist setup, but the Fox ECU seems to be happy with it
when in closed loop, open loop is just way too rich (maybe I'll just
unhook the cold start injector).

So, its over fueling in open loop mode (cold start), but runs AWESOME
onced warmed and into closed loop mode.  I still have more power to find,
I can tell its still not quite breathing right, and maybe could use a
little more ignition advance, but I can actually do 90 mph + now, and have
a little bottom end torque I never had.  I think she can make it to Cincy
now...she really still isn't fast yet, but am hoping a free flowing
intake, exhaust and maybe a little ignition timing fixes that.

So thats my story for the weekend...lemme know if you have any other ideas
of where I can find my missing power, or comments about my hackage ;).  In
the mean time, its time to do the little crap (stereo, new sport Quantum
seats, fix exhast leak at cat, etc, etc, etc, etc)

Cincy approacheth, are you greasy and pissed at your car yet? ;)

-- 
Eric
www.vintagewatercooleds.com

1979 Dasher Coupe 2.0 8v
1981 Scirocco S (TDI swap project)
1990 Corrado TDI
1990 Fox Wagon 1.6 Heron Head 8v
1991 Cabriolet (2.0 crossflow 8v project)