[s-cars] Short term rough idle - follow-up

[Robert Myers]

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Original post:

Hi Y'all,

My well modified '95.5 urS6 has developed a relatively minor but a 
bit disturbing problem.  On initial start-up the engine idles a bit 
roughly.  The idle smoothes out again after a few (perhaps 10-15) 
seconds and becomes as solid as a rock.  Obviously this is not, of 
itself, a major problem but it could be a portent of something more 
serious to come.  Any ideas/suggestions?

Other than the idle problem the car is running superbly.   Let's 
see...  modifications which might be related...  Running the Dave 
Forgie 1.8t coil mod as expressed by Apikol.  All the RS2 mods - 
turbo, ECU, EM, injectors.  Stromung exhaust.  Big FMIC, etc.

Bob

And now the follow-up:

There were several suggestions ranging from "don't worry about it" to 
"try some Techron" to "check out the ISV" to "uh-oh might be a blown 
head gasket".  (Oh joy.  :-()

OK, here's what has been done since the first post:

Item 1 - a can of Techron has been added to a 3/4 full tank of fuel 
and about half of it has been burnt.
Result 1: idle is smoother.  Not perfect yet but improved.  (It 
wasn't REAL bad to start with so...)  Indicating possible dirty 
injector(s).  I'm planning on doing the Techron bit again the next 
time I fill the tank.

Item 2 - I pulled and inspected all the NKG plugs.
Result 2 - They all looked the same - dry and with normal coloration, 
no excessive wear.  They looked as good as any plugs of that age in a 
big boost I5.  There is a hint of black deposit on the threaded 
portion of #1 well outside the internals of the engine area.  It is a 
little greasy feeling and left a smudge on the fingers.

Item 3 - The symptoms don't seem to indicate ISV troubles to me so I 
haven't messed with it (yet) - I will if the problem persists.
Result 3 - none (yet).

Item 4 - While the plugs were out I checked the compression of each 
cylinder (only one try - no repeated testing and averaging, cranking 
time was the same for all cylinders twelve pulses per cylinder) and found:
Result 4 -
Cylinder	max pressure
   1		  150
   2		  150
   3		  135
   4		  160
   5		  155

Additionally after cranking the gauge was just left alone while still 
connected to the cylinders.  The pressure held and there was no sign 
of leakage - at least not in the short term (a couple of minutes).

I'm not thrilled with #3 pressure but it is pretty close to being acceptable.

OK, whadya think?  Should I be making an appointment with my favorite 
independent Audi wrench or should I just quit picking at nits and get a life?

Bob