CIS gurus? Mind helping me out?

[mk1mark at gmail.com (Mark F.)]

On 5/22/05, C Boyko <roccit_53@scirocco.cs.uoguelph.ca> wrote:
> Okay, my 8V is making me insane. It's running like crap under load, and on
> and off either has a nice idle, or what appears to be a miss. Is that vague
> enough?


Cathy, did it just start doing this, or after you replaced some parts?

It sounds like there isn't really much else to check is there?  :) 
Hmmm, well what I'd do now (since you checked everything I would have
checked first) is to start isolating systems to chase down the
problem.  If it's a possible spark issue, maybe try temporarily wiring
the coil directly to the battery and see if it runs any better (put a
switch or fuse inline so you can shut the car off! :D).  If no change,
try running a temporary new ground wire to the coil.  You might also
want to try to ground the engine block to the chassis (I've used a set
of booster cables as a temporary "test" ground)

You may be getting a very weak spark, which may idle ok, but under
load naturally gets worse (increased cylinder pressures will make it
harder for a weak spark to spark at all).  BUT, new coil, wires, and
plugs should have addressed this possible problem.

Now if it's a fuel issue, maybe you're not getting enough pressure at
the injectors.  Have you tried testing the fuel pressure?  If you
don't have the proper equipment, a quick and dirty way of checking if
your injectors are spraying ok is to pop them out and place them in a
mason jar, turn on the ignition (or, more safely, jumper the fuel pump
relay), and lift the throttle plate in the fuel distributor.  Watch
the spray pattern throughout the range of travel of the plate for a
nice fine, even spray.

Hmmm, what else...  Are your injectors firmly seated in the bosses? 
(Sometimes new o-rings fit pretty snug in the bosses and give a false
sense of being fully seated.  I place a flathead screwdriver on the
"ridge" near the top of the injector and give it a quick tap with a
hammer to seat them).  Any other possible vacuum leaks you didn't
check?  Maybe try wiggling various hoses while the car is idling and
see if you can make it go from a nice idle to a miss.

I dunno, I'm out of ideas, but I'll let it tumble in my head for a while...

HTH,

Mark.
75
80 S
90 Audi Coupe Quattro - 10vt