[s-cars] S4 hesitates, stumbles at elevation

[Tom Green]

If it were my car, I would swap the coil pack to see if that would  
cure the problem.  Maybe you don't have another s-car or spare pack to  
swap with, but maybe your neighbor
does.  I like this approach to quickly eliminate the coils from  
suspicion.  Of course inspect the plugs and boots while doing this.  I  
would suspect a plug boot or plug first, but
my luck would be a coil.  The POS usually don't act like this.   
Determining which coil can also be a difficult proposition.

Boost leaks usually press your nose against the windshield so you  
don't soon forget what that is like, so I put it second on the list,  
but not to be ignored.  Check the boost sensor
line from the intake manifold to the ECU through the moisture trap at  
the electronics at the firewall for loose clamps or bad hose before  
checking the vacuum lines to the boost
control at the BPV and WGFV and wastegate.  If you don't find  
anything, check out the boost hoses.  Nobody said it would be easy.  :  
 > )  Hopefully, the CA mountains aren't too
far away for the road test.

Tom

> -----Original Message-----
> Date: Wed, 30 Sep 2009 11:06:13 -0700 (PDT)
> From: George Verbryck <georgeverbryck at yahoo.com>
> Subject: [s-cars] S4 hesitates , stumbles at elevation
> To: s-car-list at audifans.com
> Message-ID: <532512.21344.qm at web56407.mail.re3.yahoo.com>
> Content-Type: text/plain; charset=iso-8859-1
>
> Well my 93 S4 has been running great and I recently had a chance to  
> take it up to the mountains for an Oktoberfest event. During my  
> drive up every time I tried to pass i.e. WOT the car it would  
> stumble , retard timing or something it is hard to explain other  
> then full power was not available. Once down I gave it a few  
> spirited WOT runs on the freeway and it responded by charging out to  
> the redline no problem. I looked? for codes by blink method and got  
> nothing . Any ideas where I should start looking for the problem or  
> what the problem may be? I thought the altitude compensation on this  
> car and motronic was computer controlled? TIA , Regards, George