Volvo 740 Turbo, Gas Use and speedometer

I have a 1990 Volvo 740 Turbo sedan that’s had a lot done in the past
couple of months. The brakes have been redone, most of the exhaust
system has been replaced and it’s currently having the water pump
replaced and the coolant system is being patched for leaks. My other
problems however are gas use and the speedometer. The car manual says
that it should get somewhere near 22mpg and I figured during the
winter it wouldn’t be as good but recently it’s really been downing
fuel. With the turbo only taking premium gas and fuel prices being
where they are this has really become an annoying problem. Anyways I
was wondering if anyone has any suggestions of where to look to try
and get some better mileage. The other problem is the speedometer.
It’s been broken since I bought the car about a year ago. I did ask
someone’s opinion on it, the person who did the brakes actually. He
said that it isn’t the actual speedometer thats broken because the
odometer doesn’t work either. He thought that the speed sensor was
probably what needed replaced but regardless I figured I would get
some other opinions if anyone has any. Thanks for any advice you can
give.

 

Not terribly likely but simple to check - does the temperature guage stay
near mid-range once it warms up? If it is significantly low or wanders a
lot, a new thermostat (genuine Volvo is definitely the way to go) could make
a real difference in fuel efficiency.

Mike

 

You can run standard 87 octane fuel, the ignition sensor will retard the
timing automatically and you'll get slightly lower power and fuel
economy. It won't damage anything though. 22 mpg sounds about right if
the car has an automatic.

I've never even heard of a speed sensor failing in these cars, it's
nothing but a coil encapsulated in epoxy. I have seen the wiring from it
crumble though, and the speedometer and odometer can in fact both fail
at the same time due to solder joints on the circuit board but I would
check the wiring under the car first.

 

I found out my Speedo's problem was in the dash unit because
everything worked but the speed. Sometimes it kicks in by itself.

What I did on my 1987 740 was jack the rear up, unbolt the bar in
front of the speed sensor and then unclip the sensor connector. I cut
the connector off, leaving a couple inches of wire to re-connect.

connector, like 10-12 gauge and attached one to each wire. I then
inserted the wires with the butt connector into each hole of the
housing and re-clipped it on. This rebuilt the connector.

If it sounds confusing, when you unclip the connector to the speed
sensor, you see it is a housing with 2 female connections that clip
onto 2 male connectors. The wire butt connectors, installed over the
wire and placed in the housing act just like what was there before - a
way to clip the wires on.

G'luck!

 

simple question

How can know what the mileage is if your speedo doesn't work?

 

My odometer works fine - the speedo can go out and everything else
still work. That's how you know the speedo problem is not at the
sensor but in a speedo gear.