Date:         Sun, 15 May 2016 20:19:06 -0700
Reply-To:     Steven P Smith <kewsps@HOTMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Steven P Smith <kewsps@HOTMAIL.COM>
Subject:      Re: Miss at idle?
In-Reply-To:  <201605150844.u4F8iPLM031385@mail113c45.carrierzone.com>
Content-Type: text/plain; charset="iso-8859-1"

Thanks David,
In my case I had a pretty good idea what cylinder was a problem by the rich burning spark plug. Then I remembered that the fuel injector for that cylinder had been changed, so I replaced the injector again (turns out the replacement by someone else was the wrong injector). This did not work so, I unplugged the connector of the new fuel injector... no effect. Then replaced it and took of the adjacent injector connector and the engine died. That led me to replace the connector on the known problem cylinder and the problem cleared up. Who knows how long it will last, but I am glad I did not damage the ecu in the process.
 
> Date: Sun, 15 May 2016 04:44:23 -0400
> To: kewsps@HOTMAIL.COM
> From: dbeierl@attglobal.net
> Subject: Re: Miss at idle?
> CC: vanagon@GERRY.VANAGON.COM
> 
> At 01:08 AM 5/15/2016, Steven P Smith wrote:
> >How about pulling off a fuel injector connector. I did this recently 
> >on mine and discovered that the problem (exactly as you describe) 
> >was an intermittent bad connection inside the connector. Replaced 
> >the connector with a GoWesty kit and problem went away, hopefully 
> >for a long time. It had been an intermittent problem for at least 
> >the last 20 years. No one was able to find it. I was lucky.
> 
> I'm leary but I don't see any warnings against it.  Disconnecting the 
> ECU connector is forbidden, but the injector connectors apparently 
> not.  It's an inductive load that will kick (generate a voltage 
> spike**) if it's disconnected while an injector pulse is in process, 
> but that's what happens anyway when the pulse ends, unless the driver 
> has pulse-shaping circuits that give a slow turn-off.  Also the 
> presence of the other three injectors will tend to mitigate the 
> effect to some extent.
> 
> I just replaced the connector on my Temp-II sender, which has been 
> plaguing me for five years, and previously replaced one of the 
> injector connectors.  I think the Temp-II connection fails far more 
> often than the sender itself does.
> 
> **inductance in a circuit limits the rate of change of current in the 
> circuit because it causes energy to be stored in magnetic 
> fields.  When you close the circuit current builds up [more] slowly 
> because of the energy going into expanding the field.  When you open 
> the circuit all that energy comes back as the fields collapse, and 
> the voltage can briefly rise extremely high in order to maintain 
> current flow as an arc across the widening gap.  This is why 
> inductive loads are rough on switches.  If it's a transistor doing 
> the switching there's no arc, but a corresponding voltage rise that 
> can punch holes in the semiconductor.  When you see a relay in one of 
> these circuits with a resistor across the coil, that's one of the 
> techniques to limit stress on the transistor controlling the 
> coil.  If the relay is switching an inductive load related techniques 
> may be necessary to prevent contacts welding together as they bounce on open.
> 
> Yrs,
> d 
>