[urq] Wacky Tachy.......

Jim Fleischer jim at almgt.com
Tue Jul 28 14:24:20 PDT 2009

OK, so the car started just fine this afternoon......a little feather of the throttle to even out the idle, but settled in nicely......warmed her up, shut it down and started right up again.  Took her out for a shakedown on some local twisties......some sharp 90 degree turns down to 2nd gear, WOT to the next 90 degree, etc......stumbling from 2nd gear on up after 4K-4.5K RPM still there.....here is where once, just once, the tack pegged during the stumble, then dropped to zero, then settled back into proper RPM.   However I was not at WOT during this wacky tach experience, somewhere midway on the throttle but still hitting good boost, was around 4500 RPM, and I could not duplicate it over the next 15 minutes of shaking out.  I should note that I was driving through a pretty heavy rain with some standing water at the time of the wacky tach experience.  The rain had let up and the roads dried out during the course of the rest of my drive.

So.....I do know that the alternator is hanging low and could have gotten wet.....and maybe caused a bit of a short?  I have heard some "pup, pup, pup" sounds coming from the backside of the alternator at idle for awhile and are speed relative to rpm (this was going on before any of my recent no-start condition) that will go away when I put a bit of pressure on the backside of the alternator.  No alternator light is on (does work at start up) and the battery has been charging fine and all lights and accessories work under load.  Belts are snug and not worn nor slipping.

So, apart from the alternator sounds, was this just a one time, rain induced possible short, or indicative of an ignition issue that is causing the stumbling?  It should be noted that the stumbling used to be intermittent, but has become more consistent, like all the time now.  Boost pressure builds fine up to the stumble and throttle response is good up to stumble.  I have fixed some vacuum leaks on the intake side, and there are no whistling or wheezing sounds coming from the motor.

Even with the troubles today, it was nice to have her out again!

Any thoughts?


Jim Fleischer
'83 ur
'95 s6 avant

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