[s-cars] '92 S4 won't start

[Joshua Van Tol]

A car needs a throttle closing dashpot for a couple of reasons.

1.) fast throttle closings can lead to high oil consumption or high
unburned HC emissions.
2.) To give the idle stabilization system enough time to "catch" the engine
speed on the way down.
3.) In some cases, they're used to improve driveability of the car,
especially cars with manual transmissions.




On Mon, Jan 27, 2014 at 10:48 PM, <tedebearp at yahoo.com> wrote:

> OK, the fluctuating idle is fixed, but I can't really explain why.
>
> Fired up the car and got the same fluctuating idle as last time.  I
> wiggled the ground cable at the back of the engine and the TPS connector
> and wiring, with no effect on the hunting idle.  I reached over to the
> throttle cam to rev the engine, and as I touched it, there was a pop as the
> throttle moved by itself just a little, to the fully closed position, and
> the engine immediately settled down into a smooth idle. It looked like the
> throttle cable end was hanging up on the throttle closing dashpot:
> http://forums.quattroworld.com/s4s6/threads/23531.phtml
>
> Once I looked at the throttle cable, it was immediately clear that the
> black plastic clip at the end was broken.
>
> This is what my cable looked like, with the broken black plastic clip:
> http://forums.audiworld.com/showthread.php?t=2837004
>
> I took the car out for a quick spin and it runs well.  Pulls hard and
> smoothly at full throttle.  So all is well - for now, anyway.  No idea why
> the car needs a throttle closing dash pot, though.
>
> This explains why the engine got stuck at 4k rpm yesterday, but I still
> can't figure out why it'd cause the idle to oscillate between 1000 and 1400
> rpm.  Maybe the TPS has a bad spot and the throttle was getting stuck right
> at that spot, but I can't detect any hiccups in power delivery.  Next step
> will be to clear the codes, drive the car, and scan codes again.
>
> Thanks for all the help.  I'd have gotten rid of the car a while ago if it
> weren't for this list.
>
> Sent from my iPad
>
> > On Jan 27, 2014, at 12:29 PM, Tom Green <trgreen at comcast.net> wrote:
> >
> > Teddy,
> >
> > Cleaning the contacts on the throttle switch might improve things.  If
> you remove the switch, you need to get it back in the same position or
> recalibrate.  The connector housings and replacement pins are available
> from efiexpress.  Marc Swanson also sells the CPS sensor.
> >
> >
> http://www.efiexpress.com/catalog/index.php?cPath=7&osCsid=a40e89383dadf16f72dc55f60562d3cc
> >
> > Tom
> >
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