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Timing, backfiring and low idle.
Propane is also good for finding vacuum leaks.
Cheers.
Marc
>
> First off, timing does not make your car run lean. So, start by setting
> the timing back to factory spec.
> Second, as Jim suggests, make sure your frequency valve is humming then
> set the idle mixture. Good to have a dwell meter to set this, but if not
> set it so the engine has the highest idle speed.
> Is WD-40 flammable? I don't think it is, so how would that help to find
> vacuum leaks? I know carb cleaner sprayed at a vacuum leak will make the
> engine rev, but don't understand how non-flammable will help?
>
>
> From: "Edward Effinger" <Eeffinger@conestogac.on.ca>
> Sent: Wednesday, May 24, 2006 1:37 PM
> Subject: Re: Timing, backfiring and low idle.
>
>
> I'm fighting with my car doing a lot of that at this very moment.
> Have played with the timing a bit as a noticed the plugs were all very
> white
> rather than the usual light tan color.
>
> I retarded the timing a fair bit and the car runs better, but the idle
> speed is too low.
> I could get the idle speed up by advancing the timing, but I'm concerned
> about running too lean.
>
> Played with the idle adjustment valve last night, it didn't see to respond
> properly, although now
> the car has absolutely no power at low idle, takes a bit before the revs
> begin to build in order
> to drive off.
>
> I've checked for intake leaks by spraying WD40 around all the hoses and
> didn't find any leaks
> other than a very slight one on the air hose to the throttle body which I
> snugged up.
>
> The car also seems to miss/hunt at any speed and the exhaust pipe is quite
> sooty looking.
>
> Lots of mixed signals here.
>
> I welcome any tips/tricks to sort this baby out.
> Cheers
> Ed '81S 1.7 with no cat and aftermarket exhaust and headers.
>
>
> >>> "Brian Spinney" <vw_85roccoZ400@hotmail.com> 2006-05-24 8:05:51 AM >>>
>
> My first 85 Scirocco use to do it alot on both downshifting & hard
> acceleration up until 2500 rpm. My exhaust wasn't anything special, just
> an
> Autotech 2.25 CatBack system and a header.
>
> It definitely turned heads when I was in high school. I would roll into
> the
> parking lot and downshift into second with waaaaaaam pop, pop, pop, pop,
> ummm pop, pop, pop, pop.
>
> The car was running alittle richer than stock but I didn't think much
> about
> it at the time, or for that matter much about CIS or cars. I did my own
> oil
> changes and brakes and that was about all. It wasn't until my Senior Year
> that I started learning more.
>
> Brian
>
> 85 Scirocco 8vT 01 Jetta 20vT 84
> Rabbit GTI
>
>
>
>
>
> ----- Original Message -----
> From: "C Boyko" <roccit_53@scirocco.cs.uoguelph.ca>
> To: "Scourge" <scourge@cogeco.ca>
> Cc: <scirocco-l@scirocco.org>
> Sent: Wednesday, May 24, 2006 6:35 AM
> Subject: Re: Tech'ish question. Inquiring minds want to know.
>
>
> > Klaus did it a lot before this functional fuel distributor, so that
> means
> > three holes were likely rich, one likely lean, nobody burning all the
> > gazzzzz....pop pop pop... (so perhaps Blackie's just not misfiring like
> > previous incarnations?)
> >
> >
> > The popping's not so bad now (he's lean) So I'll report back when I
> start
> > turning that screw righty richy....the exhaust is free flowing I'd say
> > (2",
> > no cat), and is obviously capable of sounding like it'd been into the
> bean
> > burritos...
> >
> > Cathy
> >
> > On 11:27:05 pm 05/23/06 "Scourge" <scourge@cogeco.ca> wrote:
> >> Hmm..... odd. Blacky doesn't do it at all ..... at least not that I
> >> can hear. I think I'm even running a touch on the rich side right now
> >> too.
> >> About the low backpressure response. I'm currently running the Dual
> >> Out mani, TT long DP, and TT 2" w/ no cat ..... where as my old golf
> >> that went nuts with it was stock save the muffler(N/A diesel muffler,
> >> haha, sounded like a dirtbike) it was definately not free flowing,
> >> lol.
> >> I agree that rich during low vacuum would be a fair assesment ....
> >> but i'm not sure why some cars do it and others don't.
> >>
> >> -George -Oh, and my car didn't even do it much with an open DP(the
> >> whole "exhaust giving me the finger" fiasco on the dragstrip last
> >> year)
> >>
> >> ----- Original Message -----
> >> From: "Ron Pieper" <rapieper@yahoo.com>
> >> To: "Scourge" <scourge@cogeco.ca>; "Scirocco List"
> >> <scirocco-l@scirocco.org> Sent: Tuesday, May 23, 2006 9:45 PM
> >> Subject: Re: Tech'ish question. Inquiring minds want to know.
> >>
> >>
> >> > I can only answer by telling you my experiences with this via
> >> > Megasquirt, where I learned from
> >> > someone on their forums that you can eliminate the backfiring you
> >> > are desiring by leaning out the
> >> > mixture at VERY low vacuum levels - seen only with the situation
> >> > of zero or negative load with the
> >> > engine typically decelerating. With MS, that's really easy to do.
> >> > I leaned out that range, and
> >> > presto, no more pop-pop-pop.
> >> >
> >> > This was only evident with my free-flowing exhaust (straight
> >> > through) because a normal exhaust
> >> > muffles it greatly.
> >> >
> >> > Sooo...we can extract from that that your engine is getting more
> >> > fuel in those conditions than it
> >> > needs, and some 'explosion' is likely happening in the exhaust
> >> > system. With CIS, I reckon you're
> >> > stuck with it.
> >> >
> >> > I guess the little holes you write of could cause or amplify this,
> >> > but it happens anyway under the
> >> > right conditions.
> >> >
> >> > Dan Bubb, please shed your light here.
> >> >
> >> > HTH
> >> >
> >> > Ron
> >> >
> >> > --- Scourge <scourge@cogeco.ca> wrote:
> >> >
> >> >> So I've been wondering.
> >> >>
> >> >> What makes a car backfire? Not regular loud single shot
> >> >> backfires, but the awsome little pop pop
> >> >> pop some cars have on heavy downshifting.
> >> >> My golf used to do it like mad, I loved it. Made it sound so raw
> >> >> and hardcore, lol. Non of my
> >> >> rocco's have ever done it.
> >> >>
> >> >> One guy I know once told me it was cause by small holes farther
> >> >> up the exhaust(I guess he meant
> >> >> near the DP) that while leaking a bit would also create a sort of
> >> >> scavenging effect and pull
> >> >> some air back into the exhaust system. That air had oxygen in it
> >> >> and could then act as an
> >> >> accelerant with the bit of unburnt fuel and it would ignite in
> >> >> the exhaust, thus creating the
> >> >> "pop pop pop" when downshifting. I have no idea how accurate this
> >> >> is.
> >> >> Any thoughts/input??
> >> >>
> >> >> -George -missing crazy things my golf could do(like shoot flames
> >> >> out the tailpipe!)
> >> >> _______________________________________________
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> >> >
> >> >
> >> >
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> >>
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