740 turbo just stops

[John Robertson]

My wifes 1988 740 turbo just stops I fiddled with the air mixture control cleaned it and the throttle body. Cleaned all most all electrics with dialectric grease .Opened connections and made sure they are tight but still it stalls when it wants to .It seems better for a while isf I thrash it a bit in the lower gears .But ulimately it returns to a rich mixture and dead .At least now it starts when its dead .It appears to happen when the car is slowing to a stop .The Volvo boys are stumped and so am I .

 

[James Sweet]

My wifes 1988 740 turbo just stops I fiddled with the air mixture control
cleaned it and the throttle body. Cleaned all most all electrics with
dialectric >grease .Opened connections and made sure they are tight but
still it stalls when it wants to .It seems better for a while isf I thrash
it a bit in the lower >gears .But ulimately it returns to a rich mixture
and dead .At least now it starts when its dead .It appears to happen when
the car is slowing to a stop .The >Volvo boys are stumped and so am I .

Unplug the air mass meter, does it start then?

If that's ok, check the engine wiring harness, '88 is right on the threshold
of when they changed to insulation that doesn't crumble. When I cut open the
harness on my '87 I was amazed it ran as long as it did, there were bundles
of literally bare wires, the insulation turned to dust and crumbled off and
eventually ignition and injection wires were shorting together and causing
random weird behavior and stalling until one day it just shut off and
wouldn't start.

 

[John Robertson]

HORRID THOUGHT BUT YES I WILL THANKS JAMES. I uplugged the air mass meter
and it then rans so I cleaned the terminals on the lead and the meter .Its
idling a bit fast but running well but tomorrow who knows ?

 

[James Sweet]

HORRID THOUGHT BUT YES I WILL THANKS JAMES. I uplugged the air mass meter
and it then rans so I cleaned the terminals on the lead and the meter .Its
idling a bit fast but running well but tomorrow who knows ?

That sounds like a bad air mass meter then, but it's worth checking the
wiring as well. Fixing a rotten harness is not impossible, I did it on the
street in front of my house while it was snowing, I was really wishing I'd
done it in the summer when I noticed it was starting to crumble.

 

[John Robertson]

Just now its running well reset micro switch on throttle body cleaned air
mass meter contacts and fiddled tuning as wel, as base idle which was too
high .
Two days its running well are but tomorrow ?Its running very sweet actually
smooth and reactive .

 

[James Sweet]

Just now its running well reset micro switch on throttle body cleaned air
mass meter contacts and fiddled tuning as wel, as base idle which was too
high .
Two days its running well are but tomorrow ?Its running very sweet
actually smooth and reactive .

Do inspect the wiring harness though, when mine was failing that's how it
was, it would act up one day, then I'd fiddle with something and it would
run like new for a few months, then act up again, then it started having
issues more often until one day it just stalled and wouldn't start.

 

[John Robertson]

My wifes 740 Turbo is running well it was adjustment of the micro switch on
the throttle body resetting the base idle and altering the mixture which now
is running neither rich or lean .Cleaning up various contacts such as on the
Air mass meter and other switches and contacts helped .The electronic idle
control contacts and internals as well .The throttle body is just a normal
proceedure every so often .She drove many klm on sunday with no issues so
its now 4 days no hiccups .Oh the wiring is interesting in places as well so
that is now more secure ,thanks James .