Date: Tue, 26 Jun 2012 18:23:05 -0700
Reply-To: neil n <musomuso@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: neil n <musomuso@GMAIL.COM>
Subject: CO Adjusting Screw, Throttle Valve Switch Test Light Video etc.
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Hi all.
Have been having some success.
The TB seal may have been leaking. I had replaced it, but recall not over
tightening the 2 screws. That and-OR a combination of well intended anti
seize compound and lube oil for throttle shaft dripping down onto things
may have caused the Phillips screws to come loose.
I checked the seal, cleaned things up, tightened those 2 screws til the TB
almost touches the air intake distributor ears. Like I made gooten-sure the
gasket is compressed. (but not too tight)
Idle seems more even. With ign. off, disconnected O2 and idle stabilization
circuit, set idle to ~ 850 RPM, played with CO screw til things sounded ok.
Then, with a DVOM connected to the single O2 sensor lead, engine warm at
idle, sensor showed voltage hovering around 0.8 volts but fluctuated at
times. Opening and holding throttle, the O2 voltage output would be a
steady ~ 0.9 volts. (would an analogue VOM be better for this test?)
Revving engine to 3K RMP, then dropping it to idle seems to cause the O2
sensor to go to 0 volts but for less than 1 second. Turning CO screw out
too far, idle gets a *little* rough, but doing this appears to lower the
output voltage of the O2 sensor.
As for the throttle valve switch, I connected a test 12V LED. The logic is
reverse, but the test light shows that the TVS closes, opens, closes as it
should (idle, mid-higher RPMs, WOT).
Here's the video of the TVS test light connected, me driving, engine lid
off. You can see the LED ~ mid screen.
http://www.youtube.com/watch?v=IQwCxo9Mzho&feature=relmfu There may be lag
time between sound and light, (thank you youtube) but it should show that
the TVS is working.
Thanks again for all the help. I'm learning.... albeit slowly!
Neil.
On Thu, Jun 21, 2012 at 9:21 PM, Dennis Haynes <d23haynes57@hotmail.com>
wrote:
The setting of the idle mixture adjustment screw and even the operation of
> the air flow meter can be somewhat tested using the O2 sensor. The screw
> should have almost no effect at any speed above say 1200 to 1500 rpm. The
> throttle switch should be closed when the throttle is closed or at full
> throttle, not in between.
>
> With the O2 sensor disconnected from the ECU, the ECU will use RPM and the
> AFM to set fuel mixture. Measuring the voltage from the sensor to ground
> will give a reading. You may have to drive a bit to get the sensor warm
> enough to work. Ideally you should see ~.5 volts. If you rev the engine and
> then close the throttle to activate the switch you will see the sensor go
> to
> 0 during fuel cut off. In normal operation the sensor is ignored for a
> short
> period after fuel cut off. This is why that idle surge occurs if all the
> basic settings are not correct.
>
> Surging during closed throttle indicates that some combination of air and
> fuel is getting into the engine when it shouldn't. Vacuum leaks after the
> throttle or AFM can account for the air. Fuel can be leaky injectors or
> even
> oil getting sucked past the rings or intake valve guides. Those white
> crystals on the spark plugs could be oil or antifreeze. I suggest oil
> analysis just to be sure it is not antifreeze.
>
> Dennis
>
--
Neil n
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