[V8] ISV, dashpot, and clutches

[Steve Buchholz]

From what I've read the dashpot is only there to prevent NOx emissions due to high vacuum at the intake when the throttle shuts at high RPM, as happens often with a MT vehicle.  Slushers don't see this sort of behavior often so they don't have the dashpot.

My white car has been displaying high idle from time to time, now that I'm thinking about your note I'm suspecting the dashpot ... I suppose it could be a sticky throttle rod or the ISV

As to your clutch musings, I would doubt that shifting into a higher gear with the RPMs too high would not cause much more wear over time, a long as you weren't slipping the clutch.  Slipping is the main issue, and by looking at the condition of the fingers on the pressure plate you can see if it may have been due to a throw out issue.  Contamination with engine oil or brake fluid would be my next suspicion, followed perhaps by a weak pressure plate.  No matter what the root cause is slippage.

Steve Buchholz (mobile)

----- Reply message -----
From: dsaad at icehouse.net
Date: Tue, Apr 10, 2012 7:57 am
Subject: [V8] ISV, dashpot, and clutches
To: <v8 at audifans.com>

So I replaced my clutch a while back and have been wondering why it failed
after only about 70K miles.  I started noticing that I have developed a
strange technique for shifting because the engine speed does not drop for
several seconds after removing my foot from the gas.  I can't remember if
it has always done this, but I think it has.  I removed the "dashpot"
completely after adjusting it to its minimum setting and not seeing much
change.  No real change in how the RPMs dropped as far as shifting is
concerned, but there was a noticeable shock/clank to the drivetrain when
coming off the gas.  The dashpot is definitely there for a reason - so I
put it back in and at the same time put some oil in the IAC just because I
thought it would be smart.  Now, about 5 miles into my drive to work, the
ISV appears to be stuck or dead.  This makes the car surprisingly hard to
drive.  It is impossible to shift without a serious clank to the
drivetrain as I engage the clutch - unless I really rev it high, but
coming off/on the gas in gear results in a big clank every time.

Insert lots of expletives here.

film at eleven...

Dave


btw, do the automatic cars have a dashpot?

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