Date: Wed, 25 Jun 2014 03:08:59 -0400
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: Inconsistent stumbling on resume throttle..Was "vanagon
syndrome?"
In-Reply-To: <CAHTkEu+Bi_wMmU_waHey7Axg4gDSuJRhRR5UCWuDOAEV0NkRWg@mail.gmail.com>
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The symptoms clearing after cycling the ignition switch is classic of a problem with the O2 sensor or circuit. Sensors do get intermittent and they are easily fouled by road stuff on the outside and worse oil or antifreeze on the inside. Rich mixtures for any reason can also cause them to carbon foul.
On the Vanagon Digifant another common problem is a bad ground for the O2 reference circuit. One of these connections is the ground wire in the harness to the distributor. Check the archives. I have written the procedure to test the O2 sensor wiring in the past. If it can’t be found I can re-write.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Don Hanson
Sent: Tuesday, June 24, 2014 10:49 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Inconsistent stumbling on resume throttle..Was "vanagon syndrome?"
84 vanagon with 92 inline VW digifant motor and vanagon engine managment parts...
I queried "what was Vanagon Syndrome" a few days ago, thinking mine was showing what may be those symptoms...and got a few suggestions based on the
symptoms I posted. Just got in from another drive of about 100 miles,
during which I tried to induce these symptoms and get some sort of consistent behavior to pass on for you who're inclined to try to diagnose..
.The bucking and missing and bogging that I saw just two times prior to my previous post...that was occurring much more often on today's trip, but still not every single time I did ....anything I can think of....It's now something I must fix before I can use my Vanagon again...with any peace of mind...
What I am seeing quite often is once the motor is warmed up after about
15 or 30 miles and I let off the gas a little then resume throttle, not full throttle but just reapply the gas...the engine bogs and burbles and we lose speed...There is no smoke from the pipe...full throttle doesn't clear it up, nor does downshifting and going to redline....But if I switch off the ignition and turn it right back on, everything clears up in a second or two and it runs fine...then it may or may not repeat that same behavior next time I let off and resume throttle...or it sometimes just begins to burrble sputter and miss again...I think this behavior is throttle-related...but I am guessing because it isn't consistent or repeatable by anything I have been able to try to induce the behavior...
Ok, more...when I simply shift into neutral and coast for a bit, then go back to a gear (5sp manual trans) I don't think I get any missing or bucking...but if I coast down with little or no throttle, then it often (but not every time) happens when I resume throttle...
When this odd behavior is not happening, the van runs perfectly, I can go through all the gears, taking it right to redline each time and is simply purrs! Then 10 miles down the road I might come up behind a slow truck or encounter a slight downhill and I let off a little on the gas....and it begins to buck and miss....much more often today, but still not each and every time I slow up....
It is almost like there is some sort of vacuum leak...but I don't think there's anything vacuum related in the Vanagon digifant engine management, is there? Or perhaps it's related to the throttle switch...but isn't that a 'yes or no' device? On or Off...? I don't see that causing an inconsistent poor running condition, and one that can be temporarily cured by shutting off and on the ignition switch...
Anyone care to make a stab at this? Or perhaps give me a direction to
begin my searching? I do have a spare almost everything...I am going to
try swapping the Brain, the coil, and the Temp II sender and I will probably order a new Throttle switch......I just recently replaced the fuel pump and the filters...not related to this poor running...
Thanks if anyone cares to respond... Don Hanson
