Date: Thu, 12 Aug 2010 13:53:44 -0700
Reply-To: "Mike \"Rocket J Squirrel\"" <camping.elliott@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: "Mike \"Rocket J Squirrel\"" <camping.elliott@GMAIL.COM>
Subject: Re: AFM intermittancy result?
In-Reply-To: <148301cb3a57$a26ded30$6401a8c0@PROSPERITY>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Okay, so my van's 3 to 4 second loss of power would not have been due to
a slight problem in the AFM.
That said, I just opened it to inspect the track and found that the lid
had come partially open sometime between now and the last time I had it
open -- the RTV had let loose and quite a bit of dust had gotten inside.
I blew it out and inspected it and the track appeared to be clean and
undamaged. I applied voltage to the track and observed the voltage on an
oscilloscope on the wiper as I moved it across its range and there were
no dropouts.
The dust /might/ have been fouling the contact during those climbs, but
I'm not convinced that dust would cause such a consistent mode of
failure 'cause dust gets pushed around.
It baffles science.
--
Rocky J Squirrel
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Westrailia: (Ladybug Trailer company, San Juan Capistrano, Calif.)
Bend, OR
KG6RCR
Scott Daniel - Turbovans wrote:
> on the one clear case I had of that ,
> it was just a fifth of a second or so, just like someone shut off the
> key for an instant, then back on.
>
> on my current 85 Adventurewagon .
> it's stumbled a time or two after I drove it hour hours right at the
> same rpm ..
> right around 4,000 rpm jammin' down I-5 to get to Sacrameto before
> businesses closed that evening.
> - van ran fine on the way back in less of hurry.
>
> Then a week later in local freeway driving ...it 'stumbled' ..
> like a large hiccup at speed ...probably the ARM worn on that one spot.
>
> I had another one ...it was 'weak' right at 3,000 to 3,200 rpm.
> almost like a miss, and some people might not even notice it.
> it was a stock syncro westy, and the way the gearing and torque curve
> are, in normal driving around ...
> just easy driving, you would be right about that rpm most of the time ...
> we ended up doing a ton of things to that van ..
> new driveshaft, rebuilt trans, new starter, new clutch , repair an
> engine mounting stud in the engine case that had broken off ..with all
> that ...
> it was easy to say what'a another 500 for a newAFM ..
> and sure enough , that fixed it for that slight weakness at that one rpm.
>
> but more hiccups than large loss of power.
> the only other thing I see AFM's do is run unevenly.
> I'm gettting this 85 Westy GL all happy to sell, and I ran 6 differnt
> 1.9 AFM's on it , until I finally found one that's pretty even and
> smooth through the whole rpm/afm flap position range.
>
> I always carry a spare AFM..
> and ideally, we'd put a brand new one on every 50,000 miles or so.
> a smooth running one with high miles on it is semi-rare to me.
>
> actually, I have never bothered, but I have thought about a NOID light
> or equivilant up front that tells me when injectors are getting pulsed.
> so you can monitor fuel shut off with closed throttle on deceleration ..
> or if there is a stumble or glitch chopping the signal to the injectors,
> you'd have a way to see that for sure.
> and of course you have that with your 02 monitor system , though not
> directly reading if injector pulse is happening or not.
>
> scott
> www.turbovans.com
>
> Scott
> www.turbovans.com
> ----- Original Message ----- From: "Mike "Rocket J Squirrel""
> <camping.elliott@GMAIL.COM>
> To: <vanagon@GERRY.VANAGON.COM>
> Sent: Thursday, August 12, 2010 7:07 AM
> Subject: Re: AFM intermittancy result?
>
>
>> So a small bad spot on the AFM track would cause the ECU to shut off the
>> injectors, resulting in a full lean condition and immediate loss of
>> power. When that happens, the AFM's wiper will swing to another part of
>> the track, causing the ECU to start firing the injectors again, causing
>> the engine to pick back up.
>>
>> I wonder how many seconds that process would take -- from "Hey, the
>> wiper has lost contact with the track so I'm shutting off the
>> injectors!" to "Oops, I see contact again and will start firing the
>> injectors!"
>>
>> --
>> Rocky J Squirrel
>>
>>
>> Scott Daniel - Turbovans wrote:
>>> I think that will cause the injectors to not be fired by the ecu.
>>>
>>> it won't affect fuel pump ....
>>> since it will start and idle with no air flow meter at all,
>>> or AFM unplugged.
>>>
>>> I'm guessing that if it's not at WOT or Idle ..
>>> it depends on AFM contact to keep the injectors firing.
>>>
>>> ( ecu keeps fuel pump relay energized because it sees the engine turning
>>> from the ignition system. )
>>>
>>> Scott
>>> turbovans.com
>>>
>>>
>>> ----- Original Message ----- From: "Mike "Rocket J Squirrel""
>>> <camping.elliott@GMAIL.COM>
>>> To: <vanagon@GERRY.VANAGON.COM>
>>> Sent: Wednesday, August 11, 2010 6:05 PM
>>> Subject: AFM intermittancy result?
>>>
>>>
>>>> What will the ECU tell the engine to do if the AFM's wiper loses
>>>> contact
>>>> with the track with the engine under high load condition, throttle
>>>> depressed but not WOT (i.e., neither microswitch on the throttle
>>>> assembly activated)?
>>>>
>>>> --
>>>> Rocky J Squirrel
>>>> 84 Westfalia: Mellow Yellow ("The Electrical Banana")
>>>> 74 Westrailia: (Ladybug Trailer company, San Juan Capistrano, Calif.)
>>>> Bend, OR
>>>> KG6RCR
>>>
>
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