[s-cars] Help - Stumble, stall, and no start condition

[Tom Green]

Check the connectors and grounds, Dave.  It sounds like a bad coil  
(or the
POS chip controlling it)  when the engine starts stumbling, but the ECU
dropping communication sounds like a ground or a connector issue.  I
would start with all the coil connectors and grounds (right rear of  
valve cover)
and those to the ECU itself.  Use some stabilant 22 or deoxit if  
available.

I don't particularly like the spark plug regapping, and it may make  
trouble-
shooting more difficult.  Plug wires should check at 5K ohm with good
ends.

It could be both these issues.  If you can use the injector plugs to  
check
which cyl is missing and swap the connectors to the opposite POS and
check again, you may identify a bad coil or POS, but I strongly suspect
you have one or the other failing.   Clean the connectors and grounds
first and hope for miracles.

Is there someone close that could swap coil packs for troubleshooting or
for a trip if needed?  Or other parts for that matter?

Tom

> Date: Thu, 17 Jul 2008 23:17:48 -0400
> From: Dave Ellis <UrS4 at sympatico.ca>
> Subject: [s-cars] Help - Stumble, stall, and no start condition
> To: Scar <s-car-list at audifans.com>
> Message-ID: <48800B5C.1030808 at sympatico.ca>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
>
> I have on odd set of symptoms I'm hoping the group wisdom can  
> assist with.
>
> They just started yesterday and I'm supposed to start a week vacation
> tomorrow driving with our kayaks on the roof racks.  Needless to  
> say my
> wife is none too pleased.
>
> The last couple of months the car would intermittently drop a  
> cylinder,
> sometimes for a few seconds, sometimes for minutes.  This behaviour
> seems to get worse as the ambient temperature rose.  Higher octane  
> fuel
> seemed to help (97 as opposed to 91/92), but may have been co- 
> incidental
> or placebo-like.
>
> As of yesterday, when driving with the engine cold everything is good.
> As soon as the engine warms up and the engine bay gets heat soaked the
> stumble comes back *bad*, the car feels like it wants to stall, and if
> left to go to idle will actually stall.  Once stalled it will not  
> start
> unless it's let sit for several minutes, and then will usually start,
> only to stall once more as soon as I remove my foot from the gas.
>
> To add to this set of symptoms, the Engine Controller reports "No
> Response from Controller" after stalling when the engine's hot.  Other
> controllers I can talk to fine, so it's not the laptop or cable.
>
> When I hooked the VAG-COM up right before my test drive tonight  
> (engine
> cold) it connected just fine and was able to scan for fault codes  
> (none
> found).  I'm going to try connecting it after things cool down  
> tomorrow
> morning again and see what happens.
>
> Any ideas?
>
> I've replaced the spark plugs and gapped them small (0.030) just in  
> case
> the ignition coils are getting weak (original with 240,000kms).   
> The MAF
> looks ok though I haven't yet checked the resistance on it (tomorrow
> morning).  I just replaced the N75 valve two days ago and have checked
> all hoses for leaks (haven't pressure tested though).
>
> Once more thing to add, I had swapped in the 1.8bar wastegate spring
> which lead to some bucking at WOT and threw maximum boost exceeded
> errors so I swapped back the original spring.  It was while driving  
> with
> the new spring that the car stalled for the first time and things got
> really bad.  Co-incidental?  The car is not chipped, just stock.
>
> Any insight or suggestions welcomed!
> Dave