[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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!)
>> >>  _______________________________________________
>> >>  Scirocco-l mailing list
>> >>  Scirocco-l@scirocco.org
>> >>  http://neubayern.net/mailman/listinfo/scirocco-l
>> >>
>> >
>> >
>> >
>> >
>> >  __________________________________________________
>> >  Do You Yahoo!?
>> >  Tired of spam?  Yahoo! Mail has the best spam protection around
>> >  http://mail.yahoo.com
>> >
>>
>>
>>
>> _______________________________________________
>> Scirocco-l mailing list
>> Scirocco-l@scirocco.org
>> http://neubayern.net/mailman/listinfo/scirocco-l
>>
>
>
> _______________________________________________
> Scirocco-l mailing list
> Scirocco-l@scirocco.org
> http://neubayern.net/mailman/listinfo/scirocco-l
> 

_______________________________________________
Scirocco-l mailing list
Scirocco-l@scirocco.org
http://neubayern.net/mailman/listinfo/scirocco-l