Date: Tue, 12 Jul 2011 21:49:11 -0700
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: Digifant start up question> RPMs 'hunt around'
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re
"but all
the stuff is identical to a vanagon...in fact, I think the MAF may be right
off a vanagon.."
Vanagons don't have a knock sensor, which your system does.
and they use an Air Flow Meter, not an Air Mass Meter ( MAF )
so not quite the same.
My attention would be drawn to the Air Idle Valve I call it ..
an electronically controlled valve that the ecu controls, to solidly control
idle rpm.
this reminds me of the near endless posts about your timing.
and you have talked about this idle issue before..
and I still say ..
it is somewhat characteristic perhaps ( though obviously , new in a jetta
car it probably idled like a rock, cold or hot ) .
I think of air intake leaks,
worn intake valve guides and seals.
gummed up air idle valve ,
temp sensor 'maybe .
be nice to know what the compression is .
I would say ...resist thinking in terms of 'it's one thing ..
in every last case of some engine I work on ..
it is NEVER 'one thing.'
it is always .....and usually ...a thing or two, and 5 half-not-right
things.
it all adds up.
I would divide it into two main areas ..
one is all 'engine management' ..the electronics, sensors, *injectors* ...
throttle switch, oxygen sensor .. ...and so on..
and ...everything mechanical..
engine condition, everything about air control and intake..
everything about exhaust .
take Digifant waterboxers..
they'll run with many things out of whack..
but to be 'really, really right' ..
it ALL has to be really right.
It is, after all, 'just a blockage or leakage of fluids or electrons'.
Literally.
I would add that many people do not readily know that 'fluids' include, air,
exhaust, vacuum, etc..
gases, not just liquids.
and ..
betcha ..it's numerous minor leakages or blockages of fluids or electrons.
heck..
I get vanagons here that have been worked on to the tune of two 600 dollar
distributors..
and they are still stalling out.
What do I find ...?
minor things and adjustments that all add up.
No big expensive parts, just fine tuning and small parts .
start with the basics ..
and really..
valve guides, wear valve seals get old and don't work well...
a 'valve job' is part of a 'deluxe tune up' actually.
you could even have wonky spark plug wires ..even if they are not that old.
it *all* adds up.
but for idle control..
you think largely of 'air' ..........air only going where it belongs. And no
air getting in anywhere that it does not belong.
on my 'new' 1.8 8V engine..going in where a Tiico was ..
I expect this..
let's do the head gasket while the engine is out and it's easy.
let's leak-test all the valves for sealing ..
oh ...they're a bit not perfect..
ok....let's do a real valve job including valve seals...
and ..
things just keep growing like that sometimes..
then it'll get timing belt and tensioner..
and then we have to do the 4 oil shaft seals...
and....
and .......
Scott
www.turbovans.com
----- Original Message -----
From: "Don Hanson" <dhanson928@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Tuesday, July 12, 2011 6:22 PM
Subject: Digifant start up question> RPMs 'hunt around'
> Upon normal start up...during the day after I have driven some and it is
> not 'stone cold' or superhot...My engine hunts up and down a bit before it
> settles in to idle. This has always been it's behavior..but it is getting
> more pronounced lately..so much so that it has died a couple of times on
> it's "low swing" cycle.
>
> The engine managment is Digifant II. The motor is an inlne VW, but all
> the stuff is identical to a vanagon...in fact, I think the MAF may be
> right
> off a vanagon...I know the air box is.
>
> Anyway, there is no problem firing up the motor at any time and it runs
> great, however, I am curious as to what may be causing it to 'swing' a
> little more for perhaps 20 seconds upon start up. Maybe two or three
> swings
> before it settles down to about 900rpm normal idle... I know the Brain is
> reading input and adjusting things to find Stoichmetric mixture ratio as
> it
> hunts around like that...but which particular input might be 'going south'
> in my system to cause the swings to be getting wider?
>
> When I start up, I never use any 'pedal' to make things run or idle...
>
> Anyone care to explain what is happening ? Thanks
>
> Don Hanson
