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

Mark Strangways MarkS1234 at spamarrest.com
Mon Jan 25 16:27:08 PST 2010


My best guess would be a bothersome injector leaking a bit into the IM.
Cleans up nicely once running for a bit as you have said.
Since you have the RS2 injectors your better off than my big Delphi ones, but this is where I get my "guess"

Best of luck with it,

Mark S
On 2010-01-25, at 7:08 PM, Robert Myers wrote:

> 
> Dave,
> 
> The most noticeable symptom is a slightly rough idle which smoothes 
> out nicely in just a few seconds after start-up.  I wouldn't really 
> describe it as a miss.  The rpms are pretty solid.  It's not 
> "seeking" like what usually happens with a sticky ISV.
> 
> The engine sports a nice RS2 EM.
> 
> Bob
> 
> 
> At 07:00 PM 1/25/2010, djdawson2 at aol.com wrote:
>> Bob,
>> I dont' really agree that you are just guessing when you see those 
>> types of compression numbers.  I'd also argue the #5 cylinder is 
>> where you are going to see to most heat (not #3), especially if not 
>> equipped with a good EM.
>> 
>> The bottom end of these engines tend to be very durable.  You're not 
>> going to typically see a "miss" as a result of bad rings/cylinder 
>> walls either... a "miss" (assuming your fuel and ignition systems 
>> are working properly) is typically a symptom associated with 
>> valve/valve seat wear... therefore, not sealing as well.
>> 
>> Having a fresh head ready is always convenient on a high mileage car 
>> (porting... no way).  But yours looks pretty healthy.
>> 
>> Dave
>> 
>> 
>> 
>> -----Original Message-----
>> From: Robert Myers <bob at chips-ur-s.com>
>> To: Cody Forbes <cody at 5000tq.com>
>> Cc: S-Car-List at Audifans.Com <s-car-list at audifans.com>
>> Sent: Mon, Jan 25, 2010 4:34 pm
>> Subject: Re: [s-cars] Short term rough idle - follow-up
>> 
>> 
>> *This message was transferred with a trial version of CommuniGate(r) Pro*
>> 
>> 
>> 
>> Hmmm... Sales pitch? Have a nice AAN just sitting around waiting for
>> 
>> a suck.. er..., customer? ;-) Uh...  How much?  :-D
>> 
>> 
>> 
>> 
>> 
>> At 02:29 PM 1/25/2010, Cody Forbes wrote:
>> 
>>> *This message was transferred with a trial version of CommuniGate(r) Pro*
>> 
>>> Nah, I'd say it's fine. Cylinder 3 runs the hottest and seems to wear
>> 
>>> a bit more, but your numbers are reasonable. Without a leak down test
>> 
>>> any statement as to why that cylinder is low (piston rings, grouved
>> 
>>> cylinder wall, dirty/bent/burnt valve, head gasket, etc) is just a
>> 
>>> wild guess at best.
>> 
>>> 
>> 
>>> Time to take apart a running car? No.
>> 
>>> 
>> 
>>>  Time to casually search for a spare cylinder head to have rebuilt
>> 
>>> (and ported hehe) and ready to swap on to the car on a lazy weekend?
>> 
>>> Probably. Even better of course would be the same plan with a whole
>> 
>>> fresh, tweaked, engine going in. Then sell the old stuff when you are
>> 
>>> done and recoup some cost.
>> 
>>> 
>> 
>>> -Cody (mobile)
>> 
>>> 
>> 
>>> On Jan 25, 2010, at 1:37 PM, Robert Myers 
>> <<mailto:bob at chips-ur-s.com>bob at chips-ur-s.com> wrote:
>> 
>>> 
>> 
>>>> *This message was transferred with a trial version of CommuniGate(r)
>> 
>>>> Pro*
>> 
>>>> 
>> 
>>>> Yeah, Cody. You're right and I screwed it up.  Now the question
>> 
>>>> remains - do I need to get a new head gasket and/or valve job on the
>> 
>>>> car?
>> 
>>>> 
>> 
>>>> Bob
>> 
>>>> 
>> 
>>>> 
>> 
>>>> At 12:46 PM 1/25/2010, Cody Forbes wrote:
>> 
>>>>> *This message was transferred with a trial version of CommuniGate
>> 
>>>>> (r) Pro*
>> 
>>>>> Note that the compression gauge has a one way valve - it doesn't hold
>> 
>>>>> pressure in the cylinders, only in the hose for the gauge.
>> 
>>>>> 
>> 
>>>>> -Cody (mobile)
>> 
>>>>> 
>> 
>>>>> On Jan 25, 2010, at 11:28 AM, Robert Myers 
>> <<mailto:bob at chips-ur-s.com>bob at chips-ur-s.com>
>> 
>>>>> wrote:
>> 
>>>>> 
>> 
>>>>>> *This message was transferred with a trial version of CommuniGate(r)
>> 
>>>>>> Pro*
>> 
>>>>>> 
>> 
>>>>>> 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
>> 
>>>>>> 
>> 
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>> 
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>> 
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