Friggin' MFTS...again!

Mike Miller mikemilr at
Thu Dec 19 09:25:40 EST 2002

----- Original Message -----
From: "Brett Dikeman" <brett at>

> At 10:51 AM -0500 12/19/02, Kneale Brownson wrote:
> >>I seem to go through them every 12-18 months.  Usual failure mode for me
> >>the Temp gauge and A/C quit working. I never have seen low boost caused
> >>it.
> Then you don't have a MFTS failure.  Perhaps that's why you keep
> "going through them."  If the A/C stops because of the MFTS, the very
> same signal goes to the ECU to kill the wastegate frequency
> valve(1.2-1.3 bar tops unless modified.)

All I can say is it has fixed the A/C everytime if it wasn't working.
> >>  The last one was throwing false over-temps and no A/C. I knew the over
> >>temps were false because I would start the car at 5 deg and in less than
> >>minute, an over-temp alarm. I don't think so!
> I got the same thing a couple of days ago.  Low coolant level.  Have
> you considered a dash problem, or a faulty connector for the MFTS, or
> other wiring problem?

I would think a faulty connector or dash problem would most likely be there
all the time and not just every 1- 1.5 yrs. Unless the problem is slowly
killing the MFTS.

> >Could I get reduced boost (up to 1.5 on the OEM gauge, at WOT up hill in
> >third and fourth) and no cooling from the A/C from this?
> The low boost is wrong, unless you have modified the
> wastegate(misadjusted or changed spring.)  It should be about 1.2-1.3
> if the MFTS is sending a false-overheat.  Lack of A/C operation is
> not necessarily MFTS

I have fixed a non functioning A/C at least twice by replacing the MFTS. And
neither time did I have low boost. Agree, it doesn't *have*  to be a bad
MTFS to cause a bad A/C as there can be other things but on *my* car, I have
fixed it that way twice. I do have the WG spring from an 85 turbo in my WG.
It is a little "beefier". ( I posted spring specs to the main list in 96 as
I recall) Seemed to give me faster spool up. I swapped it in when
troubleshooting low boost caused by a bad WGFV ( I was one of the first ones
to experience it - thanks Ned for the correct fix) and just never took it
back out. The "beefier" spring did not change my low boost condition at all
so I doubt it is masking low boost caused by a bad MFTS. I suppose my
estimate of 12-18 months could actually be something like 18-24 months - I
haven't looked at receipts for exact dates. I've also replaced 3 TBVs over
the last 6 1/2 yrs - they seem to be good for close to 3 yrs.


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