[Vwdiesel] ECU Limiter

[James Hansen]

So what you`re referring to is like the turbo shuts off at some point, when
you get up in gears and it has a steady pull, then you feel a lurch like it
quit pulling?

If it's limp mode, a boost gauge will tell you the story, boost drops off to
under 5psi.  Generally, you get a mil light when that occurs.  In these
cars, anything causes limp mode, but unless your mil is on all the time, the
light definitely comes on.  It should illuminate with the motor not running
as the dash does it's diagnostic thing and all teh pretty lights light up.

 Kinked firewall vacuum lines, hose to the ecu for boost pressure
measurement by the ecu, all the pail of spaghetti on the firewall that
conveys wither manifold pressure, controlling vacuum, or boost pressure.
Sometimes I think too much flyshit on the taillight lens will cause it, when
it happens, it's hard to track down. 

 Just trace each and every vacuum hose, pressure line, etc and make sure
they don't leak nor have a kink in them.

Last time the 97 Passat did that, a mouse had eaten a hole in the boost
pressure line under the tray, by the cabin filter.  Time before it was too
much accumulated oil in the turbo wastegate controller (suck it out with a
hand vac pump), time before that was a kinked line, as the fifteen other
times before that....

-james

 

From: Stephen Kraus [mailto:ub3ratl4sf00 at gmail.com] 
Sent: January-18-11 10:05 PM
To: James Hansen
Subject: Re: [Vwdiesel] ECU Limiter

 

Its not clutch slippage,

 

It's probably a limp mode then....

On Tue, Jan 18, 2011 at 9:03 PM, James Hansen <jhsg at sasktel.net> wrote:

The 97 Passat, dead 99 Jetta, all are rev limited only, to what shows as
redline on the tach.
They pull up to a few hundred below redline without change in power.

Limits to acceleration can be fuel issues, boost issues, codes putting it
into limp, all manner of things.
Do you have access to vcds, you can map power with the dyno feature (not
sure what it's called these days) or map boost (MAP) and fuel flow on the
graphing function.

Clutch slippage can cause poor acceleration as well.

When you use the word acceleration, you mean by seat of the pants dyno, or
apparent g of acceleleration?
Available torque can stay the same, but acceleration rate drops due to gear
ratio, and it is very apparent in the top two.
-j




-----Original Message-----
From: vwdiesel-bounces at vwfans.com [mailto:vwdiesel-bounces at vwfans.com] On
Behalf Of Stephen Kraus
Sent: January-18-11 9:12 PM
To: vw fans
Subject: [Vwdiesel] ECU Limiter

Does anybody know if the ECU limits acceleration in different gears on a
1998 Jetta TDI?

It accelerates AWESOME in the first 3 gears, but in 4th and 5th it won't
accelerate as much, even floored.

Thoughts?

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