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Date:         Thu, 21 Dec 1995 14:30:28 -0500
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         "Morris H. Arthur" <marthur@gibbs.oit.unc.edu>
Subject:      Coughing solved: Attn. AFC FI owners!

5 gold stars to Kirk for debugging my problem; Honorable Mention to Stefan Ufer for saying "just pry off the cover and look at it!"

Short story: The air flow sensor consists of a copper arm that scrapes back and forth on a printed circuit board to tell the Brain how much air is entering your engine. This copper arm will eventually wear through the conductive coating on the circuit board: loss of electrical contact in this arm will cause your FI system to shut down at the related rpm range.

Symptoms: "Coughing" where the whole engine seems to shut down for momentary periods of time: almost like water in your fuel tank. Letting up on the accelerator or pressing the accelerator to the floor usually remedies the problem over the short term. i.e. this is a problem that will most likely occur at a specific rpm range---usually cruising rpms. (My girlfriend was right when she said that the Bus liked her driving better: she drove 65-70, I usually drive 55-60...)

Solution: Pry the cap off of your air flow sensor. Look at the track the copper arm makes over the circuit board as it moves with the door. If the coating is worn through at a particular spot, then the evidence is conclusive...I was able to bend the copper arm slightly such that the arc of the arm had a radius about 0.5 mm shorter than the original arc. Now, the arm is always contacting conductive material and I guess I'll be good for another 200K miles until the arm wears through the coating on its new track. I would recommend that AFC owners with more than 150K on their Bus do this trick BEFORE the coating is penetrated...

P.S. I just drove to Utah via NC, DC, New Mexico and Colorado with no performance problems on my '77 with 204K miles: no coughing or hiccups!

PPS. I'll post how my new propane heater works after visiting a few backcountry ski spots in Wyoming, Montana, and Canada....

PPPS. Who knows how to adjust the fuel/air mixture in the AFC FI? I assume it has something to do with the spring that holds the air flow sensor door closed.....

--------------------------------------- Morris Arthur < morris_arthur@unc.edu > Environmental Sciences and Engineering University of North Carolina ---------------------------------------

On 13 Dec 1995, Kirk van Druten wrote:

> Date: 13 Dec 1995 21:52:05 U > From: Kirk van Druten <kirk@lansharks.batnet.com> > To: Vanagon List <vanagon@lenti.med.umn.edu> > Cc: marthur@gibbs.oit.unc.edu > Subject: Re: Random coughing during a > > Reply to:RE>Random coughing during_ > >marthur@gibbs.oit.unc.edu wrote: > > >During acceleration and/or during cruising speeds, I sometimes get a > >momentary cough, where the whole engine seems to shut down: > > What year is your van? The symptoms sound like two different problems I've > experienced with a 79 and an 88. The first was the air flow meter in the '79. There's > a reostat (sp?) under that black plastic square just in front of the air filter > with a printed circuit board that wears out over time. I pulled (OK, pried) the > cover off and *carefully* cleaned the contacts with some contact cleaner > (rubbing alchohol) and very fine sandpaper. Seal it up when you're done with silicone > or some such goop so dirt/moisture won't get in there. It lasted another 6 mos > before it finally died and I replaced it. If the symptom occurs during a > certain RPM or throttle range, that could be it. You may have a dirty or worn > spot on the printed circuit part of the air flow meter. > > Also, see my post in the archives in Nov 95 about troubleshooting/replacing the > ECU (brain) in my 88 Westie. Let me know if you don't have access to the > archives and I'll email it directly to you. Let's hope it's not that... > > Kirk out > Kirk van Druten > LANSharks Consulting > 'How do you all read so much mail?' > > -------------------------------------- > Date: 12/7/95 2:42 PM > To: Kirk van Druten > From: marthur@gibbs.oit.unc.edu > OK, I've avoided this problem for two years because of the diagnosis > difficulties, but now it's occurring more regularly. > > During acceleration and/or during cruising speeds, I sometimes get a > momentary cough, where the whole engine seems to shut down: like either a > momentary lack of power to the fuel injection system or a sudden blockage > of fuel flow. The whole bus shudders and shakes for one/two seconds and > then resumes normal (smooth) operation. > > This is a tough one to debug because the problem never occurs during idle > or engine revving and only randomly on the road... > > I've already done full tune-ups and replaced the fuel and air filters. > > I'm going to check: > 1) Foreign matter in the fuel tank > 2) Fuel pressure. > 3) Systematic check of FI components. > > My plugs are black--but not gunky or oily--could I be running too rich at > times to cause random coughing ??? > > Other suggestions ? > > --------------------------------------------------------- > Morris Arthur < morris_arthur@unc.edu > > Environmental Sciences and Engineering > University of North Carolina > > > ------------------ RFC822 Header Follows ------------------ > >From lenti.med.umn.edu!vanagon Thu Dec 7 07:01:29 1995 remote from > wombatnet.batnet.com > Received: from mhub2.tc.umn.edu by batnet.com (4.1/SMI-4.1) > id AA13469; Thu, 7 Dec 95 07:01:29 PST > Errors-To: gsker@lenti.med.umn.edu > Received: from lenti.med.umn.edu by mhub2.tc.umn.edu; Thu, 7 Dec 95 09:02:37 > -0600 > Received: from halfdan (halfdan.med.umn.edu) by lenti.med.umn.edu; Thu, 7 Dec 95 > 09:04:04 CST > Date: Thu, 7 Dec 1995 09:04:01 -0600 > Received: from (localhost) by halfdan; Thu, 7 Dec 1995 09:04:01 -0600 > Message-Id: <Pine.CVX.3.91.951207091942.6382A-100000@gibbs.oit.unc.edu> > Errors-To: gsker@lenti.med.umn.edu > Reply-To: marthur@gibbs.oit.unc.edu > Originator: vanagon@lenti.med.umn.edu > Sender: vanagon@lenti.med.umn.edu > Precedence: none > From: "Morris H. Arthur" <marthur@gibbs.oit.unc.edu> > To: Multiple recipients of list <vanagon@lenti.med.umn.edu> > Subject: Random coughing during acceleration/cruising (2.0l FI) > X-Listprocessor-Version: 6.0c -- ListProcessor by Anastasios Kotsikonas > > > >


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