re. Wont rev above 1500 RPM then cooled, continued.

[ben swann]

Leif,

I just re-checked the Wiring diagram.  There are leads from each of the
two sensors into the ECU(Ox control unit).  I'm not sure what function
each performs.

The Bentley diagram refers to the MTFS as the Electronic thermoswitch.
It has leads which go to AC, ECU, Coolant temp guage and a lead which
also ties in with the coolant reservior level switch.  I did not see
any relationship right off with the afterrun circuit, but I thought it
provided some control there too.

I do recall replacing the MTFS on '87 5ktq and it did have an effect on
improving fuel mileage as well as driveability.

I thought the temp sender was for the guage, but was incorrect, as it
has a lead into the ECU as well.

Hope that clears things up.

Ben
----- Original Message -----
From: Leif Karlsson <leif.karlsson at mbox332.swipnet.se>
Date: Sunday, June 8, 2003 6:05 am
Subject: Re: re. Wont rev above 1500 RPM then cooled, continued.

It was (is) my impression that the MTFS *is* the sending unit for the
temp. gauge (and some other things, like a warning light above 120C) and
that the small one on top is connected to the fuel & ignition system. Is
this wrong? It's the one on top that I replaced (and it was broken
anyway).

I fixed the wiring to the MTFS just weeks ago, that didn't change a
thing (of course, the sending unit it self may be bad too).

Leif

ben swann wrote:
>
> Did you replace the Multi-Function Temp sensor (MTFS) on the bottom of
> the cooling neck, or the sending unit for the temp guage?  The error
is > a bad MTFS.
>
> Ben
>
> Date: Sat, 07 Jun 2003 14:34:56 +0200
> From: Leif Karlsson <leif.karlsson at mbox332.swipnet.se>
> Organization: Disorganization
> To: quattro <quattro at audifans.com>
> Subject: Wont rev above 1500 RPM then cooled, continued.
>
> Ok, Im still having trouble with this one.
>
> I have checked the idle switch: Works just fine.
>
> So I pulled the error codes. It told me that the temp. sensor is bad.
I> also got an error code that I don't recognize: 3434 (or possibly,
4343),> anyone know what this on is about? Anyway, the last one don't
seem to> appear again.
>
> So I replaced the temp. sensor, still no good: The old one was
> definitely bad, the new one however gives me correct readings (about
> 2500 then cold and ~300 then warm) but the ECU still tells me that the
> temp. sensor is bad... And it doesn't run like it should then cooled,
if> anything it runs worse like there wasn't a temp. sensor at al.
> > Bad wiring comes to mind, is there a good way to test if the ECU
signal> gets through al the way to the temp. sensor? Or is there
something else> that can make the ECU think that the engine is warm
then it really isn't> and therefor make it believe that the temp.
sensor is bad?>
> Any ideas are welcome.
>
> Best regards,
>
> Leif