Date:         Sat, 31 Mar 2007 13:34:11 -0400
Reply-To:     mordo <helmut.blong@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         mordo <helmut.blong@GMAIL.COM>
Subject:      Surging between 1700 and 3000 rpm
In-Reply-To:  <460E8FCE.2050808@cox.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Thanks for the replies, all.

I have no one to drive or monitor fuel pressure so , no, I haven't done that
yet. I guess a long piece of hose would work.

Airic, what do you mean by ignition control?

o2 sensor has no impact.

It certainly seems temperature related. From cold start, everything seems
normal. When it gets up to normal operating temp, the trouble begins. Would
either temp sensor cause such a dramatic effect?

I tend to think you're right, Mark. I just don't understand what might cause
a consistent surge and drop-off of fuel supply.

I'll keep at it with a pressure test while driving. BTW, driving with the
lid off is very enlightening as to the sounds the engine makes while
running.

cheers,

---------- Forwarded message ----------
From: Mark Drillock <mdrillock@cox.net>
Date: Mar 31, 2007 12:43 PM
Subject: Re: Surging between 1700 and 3000 rpm
To: mordo <helmut.blong@gmail.com>
Cc: vanagon@gerry.vanagon.com

At this point, just unplug the switch. It is not really much needed for
normal driving under load and then perhaps you can decide if it is a
factor in your problem.

It sounds more like a possible fuel supply problem to me. The system
pressure is dropping too low when the engine is under load and more fuel
is needed than is being supplied to the injector rails. Then the rpms
drop and less fuel is being injected so the pump has a chance to catch
up with fuel demand and the system pressure is normal again until the
demand again exceeds the supply a sort time later.

Did you closely check the fuel pressure while driving and while the
surging was taking place?

Mark

mordo wrote:

> I'm bumping this post in hopes for some diagnostic help.
>
> I thinkn calling this condition "surging" was inaccurate on my part. It is
> actually just momentary loss of power.
>
> The condition presents with the engine warm, and the engine under load. I
> have tested fuel pressure at the T and it is at spec.
>
> I am thinking that the throttle valve switch is a possible culprit. My
> question now is what is "full throttle"? If the switch is defective or
> misadjusted, would the switch out of adjustment cause this momentary dying
> condition under full throttle?
>
> I've just checked continuity and adjustment of the TVS and it appears to
> function properly. Given where the throttle is when the the swithc closes
> for full throttle, I would guess that the TVS is not related to this power
> loss. The throttle valve is open to its stop when the switch closes.
>
> To recap:
>
>
>   - 2.1L wbx with Vanagon syndrome harness installed
>   - Idles fine
>   - Under load, at about 1500-1700 rpm, the egnine dies and then revs up
>   to about 3000 rpm. Dies, revs. Dies, revs.
>   - If I hold the throttle steady it does this very consistently
>
> I'm at a loss. Any ideas?
>
> Thanks,
>
> mordo
>
>
> ---------- Forwarded message ----------
> From: mordo <helmut.blong@gmail.com>
> Date: Mar 25, 2007 4:31 PM
> Subject: Surging between 1700 and 3000 rpm
> To: vanagon@gerry.vanagon.com
>
>
> I just went out for a drive, the third short trip of the day. The van ran
> fine the first two trips except on a fairly steep grade near my house. On
> this grade, the engine loses power and drops to about 1500 rpm. By
> feathering the throttle, I could get it to rev up again and get me home.
>
> This third trip, the engine consistenly surged between abot 1700 and 3000
> rpm at about 25-30 mph. This is an automatic 2.1L wbx. Feathering the
> throttle seemed to have little positive effect. Accelerate from a stop and
> rev up to about 3k rpm - it dies and drops to about 1700 rom and then it
> goes right back up to about 3000rpm. A moment later, it drops back to 1700
> rpm and so on.
>
> I would be willing to believe it is a clogged fuel filter but why would
the
> surging be so consistent?
>
> The engine idles fine. The engine is warm, not full on hot.
>
> I checked the fuel pump wiring before this trip. A good wiggle on all
> connections did not produce any negative effects. The fuel filter is a
> clear
> plastic, round filter in frotn of the pump. It seems to have some strange
> muck at the bottom side of the filter.
>
> Any lucid insights, list?
>
> --
> mordo
> 1990 Carat
>
>
> --
> mordo
> 1990 Carat
>


--
mordo
1990 Carat