Date: Fri, 18 Feb 2005 20:53:20 -0500
Reply-To: "Adam H. Behle" <tikiman2@COX.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: "Adam H. Behle" <tikiman2@COX.NET>
Subject: Re: AFM ADJUSTING
Thanks for the AFM info. I recently have had idle problems and rich running conditions with my
87 Westy. I tried checking everything per Bentley, replaced vac lines, grounds, etc. Swapped out
idle stabillizer unit with a good one, tested oxy sensor per your instructions, and replaced all the
usual tune up items with no luck. Finally gave up and took it in to my mechanic. He checked the
fuel pressure and swapped the ECU, but no luck. Finally swapped the AFM and said it fixed it.
Before shelling out $550 for a new one or $200 for a rebuilt unit, I wanted to try re-aligning the
AFM track/arm and cleaning the unit, which ended up doing nothing. Then I tried tightening (I
think) the spring by turning the wheel counterclockwise about 6 clicks and it worked! Great idle,
lots of power, better than it has ever been before-BUT it is running extremely rich. Tailpipe is
really sooted up, nauseating smell and fumes, etc. Interestingly, mileage seems to have only
decreased 1-2 mpg.
My qustion is...do you think I can get my AFM back into whack by performing your adjusting
technique, or do you think it is too far gone and I should cough up the cash for a rebuilt one?
There are paint marks where the spring was originally, but the engine would not keep an idle-it
would get progressively worse the more clockwise the spring wheel was turned. Any help from
anybody would be greatly appreciated-thanks! Adam
On Tue, 15 Feb 2005 16:09:56 -0800, Mark Keller <kelphoto@TELUS.NET> wrote:
>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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