Date: Sun, 3 Aug 2008 22:31:55 -0400
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: Heh -- I'm such a ninnyhammer
In-Reply-To: <489657A4.9080609@gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Any adjustment of the air flow that makes any difference is proof the o2
sensor circuit is not working properly. The only time the AFM needs
adjustment is after some one has tampered with it.
That said, your situation with disconnecting the O2 sensor instead of the
gauge and the resulting response tells me that the gauge is a problem in
itself.
Normally, the 1.9 engines will run fine with the O2 sensor disconnected as
long as it disconnected before the engine is started. The Leakage at the
O2 sensor input (the .6 bias volts at that op amp or transition input) is
close enough to what the ECU is try to accomplish that basically no
adjustment is being made.
Now if the O2 sensor meter draws this circuit to ground, it will lower the
voltage and the ECU will respond by enriching the mixture. Since the
voltage is not going up as it normally would with the O2 sensor working
properly, you are going into mixture run away.
Now if this is the case it is likely the meter is also loading down the O2
sensor. This will cause the engine to always run slightly rich.
I do not know the input sensitivity of the meter input but anytime
something is added to a sensor this has to be considered. The O2 sensor is
really a current, not voltage device as is most of the sensors. We test
using voltage and resistance as a matter of convenience but the ECU is
really responding to current levels at the sensor inputs.
This is where testing needs to be done with good meters and adding stuff
permanently to these circuits can be more harm than good.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Mike Elliott
Sent: Sunday, August 03, 2008 9:13 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Heh -- I'm such a ninnyhammer
Oh great -- some secret set screw buried in the AFM body. And I should
tell the shop to hook up the sniffer, unearth that screw and play with it?
Could tuning this vanagon be more complicated?
--
Mike "Rocket J Squirrel" Elliott
71 Type 2: the Wonderbus
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
KG6RCR
On 8/3/2008 6:00 PM Mike Collum wrote:
> Mike Elliott wrote:
>> For you guys that work on 1.9L Digijet engines -- what are the "knobs"
I
>> use for the tuning? Timing is one, what else we got?
>
> In a previous post, I pointed out that I am using a different AFM with
> my new 2.1 and I attribute that AFM to providing excellent gas mileage
> without O2 sensor input.
>
> There is a plug in your AFM that can be drilled, a screw put into the
> hole, and by pulling up on the screw, the plug will come out. There is
> a screw under that plug that can be adjusted for proper mixture but you
> would want to have the proper sniffer equipment hooked up so that any
> adjustment wouldn't make things worse. I've never messed with that
> screw ... but I know it's there.
>
> Mike
>
