Vanagon EuroVan
Previous messageNext messagePrevious in topicNext in topicPrevious by same authorNext by same authorPrevious page (August 2008, week 3)Back to main VANAGON pageJoin or leave VANAGON (or change settings)ReplyPost a new messageSearchProportional fontNon-proportional font
Date:         Sun, 17 Aug 2008 23:06:28 -0700
Reply-To:     John Bange <jbange@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         John Bange <jbange@GMAIL.COM>
Subject:      Re: Idle Relay - Idle Valve match?
In-Reply-To:  <040301c9001e$5a265410$6800a8c0@4BYCY41>
Content-Type: text/plain; charset=ISO-8859-1

> I did swap out the idle relay (controller) and it acted exactly the same > way.

Heh. Well, then I betcha' THAT'S not it! Back to the drawing board...

> Anyone (who knows these relays) think it might be a bad connection, wiring > or a ground? I cleaned things up pretty well, but it's always possible to do > more.

I'd say that grounds are ALWAYS a suspect when you have weird electrical "Heisenbugs". That was one of the alternate theories that occurred to me today.

> Why would it act up when it gets warmed up, but be OK when cold? It gets the > signal from the temp sensor obviously.

Indeed it does. The idle controller has the following connections: RED/BLK - power from ignition switch RED/WHT - power from fuel pump relay WHT/YEL - power steering high pressure switch BRN - ground GRY - coolant temp sensor RED/BLU - throttle valve switch WHT - output to idle valve YEL - output to idle valve GRN - hall generator (RPM signal)

The unit does indeed watch the coolant temp sensor, so that's always a possible source of trouble. A marginal connection could cause the trouble you describe. Excess resistance on the wire wouldn't affect the behavior of the idle controller when cold, as the temp reading starts off below whatever minimum "cold start idle adjustment" threshold there is; but as it warmed, the idle controller would perceive it as still being cold, perhaps even intermittently, causing excessive idle air bypass. A quick check of the gray wire should tell you if you have a resistance problem.

Another possibility is a gummy idle valve not responding fast enough at certain ranges of opening, but that one seems unlikely.

Probably not what you have going on, but worth mentioning: I once had a weird idle surge issue that turned out to be a loose distributor collar bolt, which I'd forgotten to tighten after adjusting the timing last. As I recall the distributor had "migrated" almost 10 degrees off...

> Does anyone have a diagram of what's going on inside this relay?

Well... I kinda have one, but it's not complete and what I do have ain't pretty! "Relay" is really the wrong word for it. It's actually a hand-tuned analog computer. It's the sort of device electrical engineers used to stay awake at night thinking about, before the advent of digital microcontrollers made solving such problems trivial. Imagine, if you will, designing a machine to keep an engine running at one of three or four predetermined numbers of revolutions per minute, with neither the ability to explicitly count revolutions, nor mark the passage of time. It's beyond me, it is.

-- John Bange '90 Vanagon - "Lastwagen" '90 Vanagon GL - "Wiesel"


Back to: Top of message | Previous page | Main VANAGON page

Please note - During the past 17 years of operation, several gigabytes of Vanagon mail messages have been archived. Searching the entire collection will take up to five minutes to complete. Please be patient!


Return to the archives @ gerry.vanagon.com


The vanagon mailing list archives are copyright (c) 1994-2011, and may not be reproduced without the express written permission of the list administrators. Posting messages to this mailing list grants a license to the mailing list administrators to reproduce the message in a compilation, either printed or electronic. All compilations will be not-for-profit, with any excess proceeds going to the Vanagon mailing list.

Any profits from list compilations go exclusively towards the management and operation of the Vanagon mailing list and vanagon mailing list web site.