90tq problems continue

[Huw Powell]

> Well I'm trying to make some progress with the 90tq
> but seem to have taken a few steps back.
>
> Yesterday I moved the O2 sensor to the exhaust
> manifold and the car seemed to run better (i.e., less
> smoke) but I think I just got lucky. Read on.
>
> After this  I went to test the current readings at the
> CIS differential pressure regulator with a little test
> jig I bought many years ago. I was surprised went the
> current meter read 0 ma. Unpluged the O2 sensor, no
> change in current.

OK, so it is not reading the OXS. A steady 0 mA is the "limp home" mode.

Check your OXS wiring for shorts, check the OXS output voltage, and as
you say later, if you can, swap in another computer.

> Removed the air boot and lifted the
> meter plate (car not running of course) to simulate
> cold enrichment. Nothing, still reading 0 ma ! (should
> have gone briefly rich at this point).

The only way the air plate could affect the current is if the
potentiometer is used for that by the ECU.  I suspect you would also
have to have a couple of other things correct for it to react - idle
switch open, WOT switch closed.  And I don't think it does this, anyway.

> I did verify
> that there is voltage at many CIS sensors when the
> ignition is on, but curiously the diff press sensor
> only read 5V when the other were 11.5-12V.

If by diff. press sensor you mean the potentiometer on the side of the
airbox, that is correct.  it gets 5v and ground at pin 1 and 3 and the
output is pin 2, varies with airplate position.

>
> Then I pulled the engines codes as some recommended;
> got 4444 (no faults) but then 1111 which is defective
> memory in computer ! I'm really bummed at this point,
> because its lookin like I fried my CIS computer
> somehow. I infer this from the code and the fact I get
> no current at the diff press regulator. Could I be
> wrong ?

What is the DPR current at a cold start?  If the ECU is working, you'll
see something around 30-60 mA for a moment, slowly dropping to 0 mA over
a minute or two.  This is the open loop warm up enrichment in action.

How is your temp sender (should be one of those awful MFS units for
CISE3)?

--
Huw Powell

http://www.humanspeakers.com/

http://www.humanthoughts.org/