Tech'ish question. Inquiring minds want to know.

[greg.rocco at gmail.com (Greg Pallett)]

There was a thread on the 'tex about various questions... here's what they say:

"What is the cause of the burbling, popping sort of sounds my car
makes from the exhaust(as distinct from mechanical or induction
noises) when coasting?
Air is being drawn back towards the engine because a vacuum formed
when you let off the throttle. every car in the freakin world does
this (beleive it or not) you just cant hear it on 99% of stock exhaust
systems."




On 5/24/06, Jim Ruffi <sciroccos@earthlink.net> wrote:
> I asked the list about this several months ago but it didn't go anywhere.
> My 8V has a somewhat open muffler and does pop on decel.  It actually
> bothers me because it appears to be a sign that I'm not running well.
>
> I noticed a couple of things: (1) it doesn't pop during the first 20 secs or
> so after the motor has been started and (2) the popping stops if you hold
> the WOT throttle switch in the engaged position.  I wrote down a bunch of
> things to check for basic diagnosis per the Bentley, but I haven't gotten
> around to it.
>
> I noodled with the ignition timing, mixture and idle quite a bit and was
> able to minimize it, but it did cost me some driveability.
>
> My mileage is 28-29, all highway, with a .81 5th, 175/70-13 tires, carrying
> about 350 pounds of cargo (including me).  I thought it should be a little
> better, which is why I'm interested in "fixing" the "problem", but I could
> be wrong.  The motor does have ~190k on it.
>
> Jim
>
> ----- Original Message -----
> From: "Dan Bubb" <jdbubb@verizon.net>
> To: "Scourge" <scourge@cogeco.ca>; "Scirocco List" <scirocco-l@scirocco.org>
> Sent: Wednesday, May 24, 2006 8:24 AM
> Subject: Re: Tech'ish question. Inquiring minds want to know.
>
>
> I've noticed the same thing that Ron has. If the fuel is a little bit too
> rich on the overrun it'll pop.
> But, I've also noticed over the years that having a small exhaust leak near
> the engine will also produce the popping.
> Since there isn't much you can do with CIS to richen it up on the overrun,
> maybe you should look into very small drill bits? ;^)
> Dan
>
>
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-- 
84 Scirocco Wolfsberg - The Red Baron aka Weekend FunWagen
91 Jetta - Still needs a name aka DailyBattleWagen