740 GL computer problems

  • Thread starter Thread starter F Murtz
  • Start date Start date
F

F Murtz

1990 740 GL Earlier today it stopped then I got it to idle.It would idle
for ages but every time i accelerated it stalled, then I managed to
start it at high revs which it would maintain but would stall when revs
dropped.
I think there is gremlin living in the computer laughing at me
Fault code says temp sensor but car has been working well except for
starting since I got it a few months ago but now it conks out
and does not want to start at inconvenient times. It seems to pump fuel.

I left it for about one hour after use, tried to start it, would not go
so I disconnected battery for five min, reconnected and it started which
suggests something tells computer to not allow engine to go and after I
wipe its memory it goes again
can faulty temp sensor cause engine to stop and misbehave in such a
manner or some other sensor?

Have not had time to install sensor as it is in the most difficult
position the designer could find
 
F said:
1990 740 GL Earlier today it stopped then I got it to idle.It would idle
for ages but every time i accelerated it stalled, then I managed to
start it at high revs which it would maintain but would stall when revs
dropped.
I think there is gremlin living in the computer laughing at me
Fault code says temp sensor but car has been working well except for
starting since I got it a few months ago but now it conks out
and does not want to start at inconvenient times. It seems to pump fuel.

I left it for about one hour after use, tried to start it, would not go
so I disconnected battery for five min, reconnected and it started which
suggests something tells computer to not allow engine to go and after I
wipe its memory it goes again
can faulty temp sensor cause engine to stop and misbehave in such a
manner or some other sensor?

Have not had time to install sensor as it is in the most difficult
position the designer could find
Click to expand...


Have you tried unplugging the air mass meter? It's a common problem that
causes exactly those symptoms.
 
James said:
Have you tried unplugging the air mass meter? It's a common problem that
causes exactly those symptoms.
Click to expand...
Is that the wide flat plug near the air cleaner and do you leave it
unplugged temporarily?
 
F said:
Is that the wide flat plug near the air cleaner and do you leave it
unplugged temporarily?
Click to expand...


Yes, and yeah, it won't run right with it unplugged, but it will start
and run in limp mode and be drivable enough to get home or to a service
shop. If the behavior improves with it unplugged then you need to
replace the part. You could try cleaning the connections, some have
reported success with that, but the only time I've had a problem, the
AMM was truly dead. It's an expensive part, but you can find used ones
on occasion.
 
James said:
Yes, and yeah, it won't run right with it unplugged, but it will start
and run in limp mode and be drivable enough to get home or to a service
shop. If the behavior improves with it unplugged then you need to
replace the part. You could try cleaning the connections, some have
reported success with that, but the only time I've had a problem, the
AMM was truly dead. It's an expensive part, but you can find used ones
on occasion.
Click to expand...
Thanks I will try that
 
James Sweet said:
Yes, and yeah, it won't run right with it unplugged,
Click to expand...

Of course, you're assuming he's got the Bosch fuel injection system.
My 1990 740GL is Rex/Regina, and doesn't have an air mass meter,
just an intake air temp sensor (as he said) "near the air cleaner".
I guess it depends on how wide his "wide flat plug" is.
 
: James Sweet wrote:
: > F Murtz wrote:
: >> James Sweet wrote:
: >>> F Murtz wrote:
: >>>> 1990 740 GL Earlier today it stopped then I got it to idle.It would
: >>>> idle for ages but every time i accelerated it stalled, then I
: >>>> managed to start it at high revs which it would maintain but would
: >>>> stall when revs dropped.
: >>>> I think there is gremlin living in the computer laughing at me
: >>>> Fault code says temp sensor but car has been working well except for
: >>>> starting since I got it a few months ago but now it conks out
: >>>> and does not want to start at inconvenient times. It seems to pump
: >>>> fuel.
: >>>>
: >>>> I left it for about one hour after use, tried to start it, would not
: >>>> go so I disconnected battery for five min, reconnected and it
: >>>> started which suggests something tells computer to not allow engine
: >>>> to go and after I wipe its memory it goes again
: >>>> can faulty temp sensor cause engine to stop and misbehave in such a
: >>>> manner or some other sensor?
: >>>>
: >>>> Have not had time to install sensor as it is in the most difficult
: >>>> position the designer could find
: >>>>
: >>>
: >>>
: >>> Have you tried unplugging the air mass meter? It's a common problem
: >>> that causes exactly those symptoms.
: >> Is that the wide flat plug near the air cleaner and do you leave it
: >> unplugged temporarily?
: >
: >
: > Yes, and yeah, it won't run right with it unplugged, but it will start
: > and run in limp mode and be drivable enough to get home or to a service
: > shop. If the behavior improves with it unplugged then you need to
: > replace the part. You could try cleaning the connections, some have
: > reported success with that, but the only time I've had a problem, the
: > AMM was truly dead. It's an expensive part, but you can find used ones
: > on occasion.
: Thanks I will try that


Hi "F. Murtz",

Regarding the "cleaning the connections" advice, wisely suggested by James,
I've enjoyed considerable success using dielectric grease on both the
sockets and the pins in that AMM and then plugging it in and out ten times.
Don't laugh! That procedure was given to me by our local Volvo dealership
technician.
It worked........

Good Luck.
Andy I.
 
MasterBlaster said:
Of course, you're assuming he's got the Bosch fuel injection system.
My 1990 740GL is Rex/Regina, and doesn't have an air mass meter,
just an intake air temp sensor (as he said) "near the air cleaner".
I guess it depends on how wide his "wide flat plug" is.
Click to expand...
Continuing saga,(I think it is regina)In the morning it kept conking out
over and over again with me disconnecting wait 5 min restart go a bit
conk out. not all morning but about 1 1/2 hours then it started and went
for the rest of the day no trouble.
So I think it is going to be murder to diagnose.
 
F said:
Continuing saga,(I think it is regina)In the morning it kept conking out
over and over again with me disconnecting wait 5 min restart go a bit
conk out. not all morning but about 1 1/2 hours then it started and went
for the rest of the day no trouble.
So I think it is going to be murder to diagnose.
Click to expand...

The plug near the air cleaner is wide and flat attached to a square
thing in the air intake near the cleaner it does not look like the small
temp sensor in a round air intake pipe that is in the picture of regina
engine but the rest looks like regina layout
PS disconnecting it did not alter its conking out behaviour
 
F said:
The plug near the air cleaner is wide and flat attached to a square
thing in the air intake near the cleaner it does not look like the small
temp sensor in a round air intake pipe that is in the picture of regina
engine but the rest looks like regina layout
PS disconnecting it did not alter its conking out behaviour
Click to expand...


An air mass meter looks like this
http://www.swedishautoparts.com/shop/catimages/Volvo-Air-Mass-Meter-8111207.jpg


Is your check engine light on? I believe 1990 is new enough that it
should have OBD.
 
F said:
Thats what it looks like And fault code says temp sensor but car has
been working since I got it with fault light on
Click to expand...


Well if you have a temp sensor fault code, then I would definitely start
with the temp sensor, if it has no signal from that it will run very
rich. Change that part and go from there.
 
You must log in or register to reply here.
Back
Top