[ba] Tech help

urquattro urquattro at phoenixdsl.com
Thu Feb 15 01:30:05 EST 2001

> I have almost completed my 4kq turbo conversion.  I
> drove it to work today for the first time.  It ran
> great except for the tach.  I am pulling the tach
> signal from the Mac-11 ecu.  At 3000 RPM the tach goes
> down to zero.  Then when the engine RPM's drop below
> 3000 it pops back up.  The ECU does not show any codes
> blinks 4444.  The output tests actuated all of the
> appropriate solenoids.  Any input is appriciated.  I
> would like to get this solved before putting the dash
> back together.

Hey there Jeff!  Congrats on getting the car back into a running state!

I guess my first comment would be that the problem has to be in the tach, as
if you were truly losing spark the car wouldn't be running (yes, I know,
DUHHH!)  You didn't say exactly how you hooked the tach up ... on a car like
my '88 5kCSQ the tach signal comes from pin 7 of the ECU, while on the 4kQ
the tach is connected where the old style "points" would connect to the
ignition coil primary.  I suspect that there is some difference between the
two signals that is causing the tach to misbehave.  I knew the MC's coil had
an integral driver, but at least from the wiring diagram it looks like the
primary lead is made available ... my suggestion to you would be to try to
connect the tach to the terminal 1 pin on the coil directly to see if it
makes the tach work as intended ...

Steve Buchholz
San Jose, CA (USA)

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