1990 740 gl continuing saga

latest symptoms, car is hard to start but after starting goes for 1/4
hour or so then conks out it sometimes starts and idles but conks out
when accelerated if I manage to start at high revs the engine runs till
I move accelerator or put in gear then it stops.I have tried an other
second hand computer , same symptoms.

I am having trouble identifying system (to check codes) The engine is a
B230F, It has a bosch comp.with these numbers 3547777 0 280 000 935,it
has an air mass meter, it has standard looking round can coil and the
distributor is on back of cam shaft.

Fault codes on socket 2 are 1:2:3 and 1:3:1 (131 does not seem to mean
anything)
Fault codes on socket 6 are 2:2:4 and 2:1:4

If it is rex regina this would mean temp sensor and rpm sensor but I am
told rex regina does not have air mass meter ???

I have changed temp sensor but old one had the same resistances
aprox 4k ohms near freezing and 210 ohms near boiling.
If it is the impulse sensor (rpm sensor) Where is it and can it be got
at.I have changed fuel filter and can hear pump and if I break fuel line
it pumps fuel but I have not measured pressure.

The temp guage reads half way after warm up and stays there.
these engines seems to run very cool and do not seem to have much
pressure even when warm you can take cap off oval tank

 

You have a Bosch LH Jettronic fuel system and Bosch ignition. The Regina
system has a square coil and no air mass meter.

Are you sure you changed the correct temperature sensor? One is for the
gauge on the dash, the other is for the ECU.

 

Yes because I disconnected the other one and the gauge did not register
that proved which is which.
My problem is which fault code chart do I use do the "Table 1: Bosch
LH2.4 and Motronic 1.8 Fuel Injection Fault Codes"? If so the 131 seems
to mean rpm sensor.

 

A bad RPM sensor would certainly lead to poor running as well. My cars
are too old to have one of those so I can't offer specific advice on it,
but usually those are variable reluctance sensors, about the only thing
that can go wrong with them is a physically broken connection, so if you
check it out with an ohm meter and it is not open, then it is probably
ok. I would guess a good one to be a few tens of ohms.

 

A2 is Fuel Side
123= ECT Sensor Signal Missing or Faulty
131= RPM Signal from Ignition Control Module (ICM) Missing @ Start
A6 is Ignition Side
224= ECT Sensor Signal Missing or Faulty
214= Engine Speed (RPM) Sensor Signal Missing Sporadically
The ECT sensor you changed where was it ?
Check the engine speed sensor there should be a color band near the
connector if yellow change
It sounds like you have a faulty engine speed sensor (Common problem)the
sensor is held in a bracket which bolts to the rear of the engine be
careful the speed sensor has been known to get stuck inside the housing
DO NOT attempt to try to use something long to loosen it up you will end
up breaking the housing & the only way to replace is to remove the
transmission
Glenn K
Volvo Certified Technician 2008
ASE Certified Technician 2008

 

In the most awkward spot the designers could think of under no.3 injector.
I have changed the rpm sensor and so far the car is going. I will go for
a run tomorrow.
Engine light still lit on dash, code on socket 2 is 123 code on socket 6
is 224 .The only thing I can see is that I probably have open circuit or
short in temp sensor wiring which is going to be difficult as I have
not got wiring diag with colour codes and following wires in looms is
difficult but at least car goes with this fault

 

There is another sensor close to the front of the engine this is what
most likely is giving you the 123 code very rarely have i changed the
sensor in the rear of the engine
Glenn K