[s-cars] Troubleshooting suggestions?

[Paul Anderson]

Greetings All,

For the first time in 16K miles of ownership, my '95.5 S6 is encountering a 
bit of a problem. (95.5 S6, 96K miles, no significant engine mods)

Starting about a month ago, I noticed that the motor was hesitating a bit 
under load at lower RPMs (~1600-2000).  More recently, under full throttle 
accelleration I've noticed the motor isn't running optimally.  The S6 will be 
accellerating fine, just up to the point where it would usually engage that 
last wonderful rush of power, and like someone flicked a switch, the power 
decreases and the exhaust note and vibration level becomes noticably rougher. 
This error condition goes away just as abrubtly if I let off the throttle a 
bit.  

My first thoughts were: ignition, waste gate, or a boost leak. However, after 
performing a little research, and considering the abrubtness of the 
condition, I'm leaning towards the ignition. Shamefully, I haven't even 
replaced the plugs since I bought the darn thing (negligent bastard that I 
am). So, over the coming Thanksgiving weekend, I'll be performing the 
following checks/service:
- Replace plugs
- Test/replace coil connectors (in case they're arcing to the head)
- Testing coils
- Replace fuel filter (in case of fuel starvation)
- Testing power output stages

I've been told that the valve cover gasket can leak and allow oil to 
comprimise the spark plug / coil connector interface.  If I find that, I'll 
add it to the list.

Any other suggestions?

Also, the owner's manual instructs the driver to downshift at 1500RPM.  This 
sounds low to me.  I suspect that this suggestion was for the V6 and I try to 
keep the RPMs above 2K.  What's the conventional wisdom on this subject?

Thanks for your assistance,

Paul
'95.5 S6

PS. No, I don't have a OBD code reader yet. Perhaps for Xmas.
PPS. I have the Bentley CD, but it doesn't run on Mac OSX. PC emulation
     software is on order. <roll_eyes>
PPPS. Servicing the old '87 5kcstq seems easy by comparison. ;-)