Volvo 740 Turbo, Gas Use and speedometer

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!

archive:

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.