Date: Mon, 3 Aug 2009 22:28:27 -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: Slight over run popping from exhaust..84 (inline VW with
Digifant )
Content-Type: text/plain; charset="iso-8859-1"
cool don,
yes, the fuel rail is plastic.
I've never had to mess with one much, but billet aluminum sounds very nice.
'old tech' throttle switches that I have seen ....
usually they mainly tell the ecu when the throttle is at idle. and WOT.
Most of the time you can just move the throttle ( engine off ) and hear the switch click, particularly for idle.
I've got the books on your engine.,
but don't want to go dig them out just now.
nice to see your note,
Scott
----- Original Message -----
From: Don Hanson
To: Scott Daniel - Turbovans
Cc: vanagon@gerry.vanagon.com
Sent: Monday, August 03, 2009 10:23 PM
Subject: Re: Slight over run popping from exhaust..84 (inline VW with Digifant )
I have two "Exhaust systems" possibles. Could be that, since the PO who did the conversion cut and re-welded the down pipe to re-direct the exhaust. He pretty 'hacked' the welding..brazing?..Wouldn't surprise me to find some leakage in there.
I have, waiting for install, a cool aftermarket billet metal fuel rail..Just $60 for the 1.8liter..I was planning on replacing the stock one, which I believe is plastic..While I am in there, I will do a spray test of the injectors..just for grins. I had the head off not long ago and the exhaust ports are perfect..Plugs read perfect, too.
It may be the throttle switch...I see one on there and read in the Bently that there is a procedure to adjust that...problem is there are about 3 different ones listed, looking very similar and all slightly different to adjust.. I have a new idle control valve and all the hoses are replaced. I have a pretty new O2 sensor also...
Thanks for the educated guesses..Now when I go after it, I will be more likely to cover all the bases...The exhaust leak didn't occur to me..
Don Hanson
On Mon, Aug 3, 2009 at 5:18 PM, Scott Daniel - Turbovans <scottdaniel@turbovans.com> wrote:
things that pop into my mind are the integrity of the exhaust system ......
no leaks anywhere, and the muffler isn't deteriorating inside , things like that.
I do like your throttle switch though .........that it's not getting the 'full' 'I'm-at-idle-now' signal to the ecu.
I find many throttle switches that won't return quite to 'full idle' every time. They get sticky or worn.
So check that for sure - any throttle position switch that it might have,
or even .........dragging throttle cable.......doesn't return fully to idle setting.
injector leaking .........sure, I like that theory very well.
Han an 84 waterboxer that backfired at idle once.........just an intermittent pop.....
watching the injectors spray revealed an obviously leaking one.
if you can just hang the injectors out and power up the fuel pump .......
( might not be that easy to do on your engine though ) ..........if you see one leaking at all, while it's not even getting a signal to fire, that's a bad injector for sure.
I mentioned recently that I had an injector issue on a waterboxer - I examined the spray pattern on 10 used injectors - only 4 of them had a nice spray pattern.
But who in their right mind would want to trade a wonderful useful vanagon in on something like a Honda Element, much as I admire them as a spunky cute useful product .........they just can't do what a vanagon can and be what a vanagon can be. I mean, you wouldn't be writing your buddies here on the list if you had one of those !
but the notion of fuel in the exhaust on overrun., being 'the cause' ......I like that basic theory as a route to explore very much.
I would consider the exhaust system itself a lot, and the oxygen sensor just pops into my mind as something to consider as well, no real reason for that .......... 'just cause' .
yeah, my two big thoughts now are physical condition of the exhaust .............starting from the exhaust ports, going to the tail pipe.
and extra fuel in there on overrun.
I'll sure say it's darn handy to be able to hang the injectors out on the fuel lines and watch them spray on a waterboxer.
Don't know if you can easily do that on your engine, without rigging something special up.
it's probably not hard to get them tested by fuel injection company, like if you bring them the injectors.
and I am leery of rebuilt fuel injectors. I would only replace injectors one at a time with rebuilt ones, never the whole set at once.
Does spark plug inspection reveal anything ..........like one cylinder looks differently than the others ?
Exhaust ports too, except those are not easy to inspect.
Scott
----- Original Message ----- From: "Don Hanson" <dhanson928@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Monday, August 03, 2009 4:30 PM
Subject: Slight over run popping from exhaust..84 (inline VW with Digifant )
I know it's not a WBX motor but it is Bosch and uses many of the same
parts as a Vanagon stocker. Plus I know there are list members with other
similar VW motors and knowledge of the Digifant EFI system. Here goes:
This particular motor is still running super. No issues other than this
recent minor irritating new behavior. Gas mileage has not changed in about
30k miles I have put on. It's an 8-valve 1.8liter VW motor from a '92
Jetta/Cabriolet/Rabbit stuck into my 5sp vanagon using diesel van
peices/parts. It has no cat and a straight through Magnaflow SS muffler.
I've recently noticed that more often than before it sometimes 'pops' a
bit, softly..on deceleration..As in: when downshifting and coming to a
stop. It has always been a little prone to this behavior , but until
recently, only when it is in 'warm up' mode..like before the idle circuit
had stopped and the idle slowed to normal..But recently it has begun to do
some very mild popping as I decelerate even when fully warmed up.....not
every time but it occurs more often if i have just done a hard acceleration,
then let off..Like in stop and go traffic. If I floor it, then drop the
throttle and coast down, it goes..bapp bap bappity put put..did-dow dow
dow....not loud but like that... It seems like there may be some kind of
throttle switch that might be 'going south' or something..allowing some
unburned fuel to pass through the motor and then maybe ignite in the muffler
or on its way out the exhaust system?..Or perhaps I have an injector that is
working at times when it shouldn't be or leaking fuel into the fuel rail
using the vacume created by deceleration?...but that would give me a loss in
fuel mileage, right?
This behavior is not really bothersome other than I've noticed it now so I
want to figure it out and put it back exactly to rights. I sometimes lately
see pedestrians lately turning as I go past, smiling at the old Hippy in the
'poopy-colored poopy-sounding' Bus.. I don't like to draw attention like
that. Some official might notice and be inspired to" help ' me and the
enviornment by legislating my 'clunker' away and giving me the
option to charge a brand new PT Cruiser or an Element or something...
Any hints or ideas where I should look?
Don Hanson
