Date: Tue, 15 Feb 2005 16:09:56 -0800
Reply-To: Mark Keller <kelphoto@TELUS.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mark Keller <kelphoto@TELUS.NET>
Subject: AFM ADJUSTING
Content-Type: text/plain; charset=us-ascii; format=flowed
Hi Marc,
I would so love to show you how to fix your van in person. I've have
written quite a bit about tuning the fuel injection system. You of
course may have other issues, but if your willing to read my procedures,
they will help you pinpoint what works and what dosen't.
First thing is how are you with using a digital volt meter? If you have
one this is a key piece of equipment.Ok, there are two ways to get the
detail instructions, 1. search vanagon.com archives of the vanagon list
under author's name contains, just enter kelphoto. That should pull up
every thing I've written years 98-2003 are the ones you want. 2. Sam
Walters has saved most of my articles, and may send you the complilation.
Just to get you thinking let me say some things about the Vanagon ECU.
What it does know. Air flow, Air temp, water temp, amount of hydro
carbons in the exhaust stream, if the engine is at idle or wide open
throttleor WOT. What it dosen't know, but belives to be at a specificed
value. Fuel Pressure and timing.
What corrupts the ECU's perception of it's world. Bad grounds, wrong
fuel pressure,wrong timing (not too likely), vacuum leaks, bad wireing
harness, wires and or connectors. Faulty sensors. Poor contacts of the
microswitches. Other issues are if the idle circuit is not working
properly, but note this circuit is only relied on when warming up a cold
engine. A warmed up engine will idle fine with it disconnected, which
rules out another failure point. i
So the critical path according to liklyhood of failure is to check the
fuel pressure. Then ensure ALL of the connectors are clean and tight.
Then check the high failure items. Temp II sensor, the wire from the O2
sensor to the ECU, common short, and a intermittant one at that. The AFM
is a variable. Carbon is used to determine resistance, and does wear
thru where the wipe arm sweeps, visual inspection is telling, look for a
white mark where it should be black. Other things are the ilde and WOT
microswitch connuity
So if I were there, the first thing I would do is to disconnect the O2
Sensor, and connect the DVM to the sensor lead, and start the engine.
The voltage should show in the first minurte or two, if not the O2
sensor needs attention first. Remove it, heat the sensor tip with a
propane touch. This will accomplish two things, it will clean the soot
off, two see if it will now generate voltage. The voltage should be
between .3 and .7 volts. The ECU ignores the O2 until the TEMP II
begins to registers, just as the temp guage touches the white block,
then the ECU goes to open loop. Email me whenever you like
Mark Keller
91 Carat
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