Date:         Sun, 21 Aug 2011 20:18:58 -0400
Reply-To:     John Lauterbach <jhlauterbach@BELLSOUTH.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         John Lauterbach <jhlauterbach@BELLSOUTH.NET>
Subject:      Re: O2-sensor blues and more on '84 1.9L engine
Comments: To: Dennis Haynes <d23haynes57@hotmail.com>
In-Reply-To:  <BAY152-ds122EDF78156F6E1B0D3FD5A0260@phx.gbl>
Content-Type: text/plain; charset="UTF-8"

Dennis,

Thank you for your help.  Shorting the engine end of the O2-sensor
connector to ground makes the engine decrease RPM, run rough, and
exhaust to smell rich.  Voltage on sensor end of connector is about 0.20
volts.  When cable is not shorted, voltage goes up a bit to about 0.25.
When both halves on connector are joined, voltage is about 0.45 volts.
However, most of that voltage is present on the engine end of the
O2-sensor cable.  Does this mean something in the ECU is wrong?

John

On Sun, 2011-08-14 at 22:29 -0400, Dennis Haynes wrote:
> There is a way to test the O2 sensor system for response. With the engnine warm and running, short the O2 sensor lead to ground. The engine should go rich. You can use the voltmeter to confirm this as the O2 sensor voltage should go up. You want to see ~.8 to 1.0 volt or more. Now connect the sensor lead to voltage source/ This should drive the ECU to make the mixture lean and this will make the O2 sensor voltage drop.
>
> As the ultimate test reconnect the O2 sensor. Measure the voltage on it and see if it is fluctuating. If it is then it it is working and your perceived richness may actually be something else such as an ignition or lean cylinder miss fire or maybe something more cylinder such as valve problem.
>
> Dennis
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of John Lauterbach
> Sent: Saturday, August 13, 2011 11:47 AM
> To: vanagon@GERRY.VANAGON.COM
> Subject: O2-sensor blues and more on '84 1.9L engine
>
> First, thank you to one of the list gurus who suggested checking on shorts between O2-cable and its shield.  I had one of my own causing.
>
> When the O2-sensor is connected and I measure the voltage between the connector and engine ignition control module heat shield, I am getting around 0.46 volts with engine warmed up.  Voltage is rather stable with engine at idle.  Am I in the ballpark?
>
> With O2-cable unplugged, resistance between connector and ground on cable to O2-sensor is infinite.  Resistance between other connector and ground on cable to ECM is 173000 ohms.
>
> I am not sure what I am missing, but engine runs well, but is running very rich.
>
> John
>