Possibly different '89 200qt power issues

[Mike_Buckham at ptk.pioneer.co.uk]

Hi everybody.

I've just joined this group because I've just got myself an '89 200qt Avant
to replace my older '86 100q Avant (which I am storing for spares). I am
having an intermittent power problem which seems to occur about 80% of the
time. When the fault is not there, the engine is sweet and there's plenty
of power. When the fault is in, the engine still has some power, but a LOT
less, and it also struggles to idle. Also, I've noticed that if you pump
down the accelerator and hold it, the revs rise initially and then drop
down quite a bit. You have to keep pumping the accelerator to keep the revs
up. This symptom may be related to the engine temperature though.

The problem comes and goes throughout a journey and so I believe it to be
an intermittent connection to the ECU from or to one of the sensors or
valves in the engine. The trouble is that I can't track the b*gger down.
Can anyone give me a suggestion as to where to look based on this
information?

My car doesn't have an engine check light wired in (I believe this is
normal for UK spec cars of this age) so I was also wondering if anyone
could tell me which ECU connections to wire a light to. This way I can
hopefully read some ECU diagnostics. It has the Hitachi MAC-12D ECU. Can
anyone tell me how many diagnostics I can read from this ECU? I believe I
activate them using the fuse connection in the fuel pump relay.

Finally (for now), I just read the email from Ben Swann ("re. More '89 200q
power problems") which indicated that the multi-function temp sensor could
affect the engine performance. I know that this is faulty on my car because
my coolant gauge doesn't work and I have traced the wiring back to that
sensor with no breaks. I have already acquired a replacement sensor from a
scrappy but haven't fitted it yet. Is there a chance that this will cure my
intermittent engine power problems?

Cheers, Mike.
'89 200qt Avant.
Reading, UK.