B230FT Fuel Mileage

[Chuck25624]

Can anyone tell me what the fuel mileage should be on a 1994 940 B230FT? I know that driving habits and conditions are a factor, but I'm only getting about ten MPG around town and thirteen to fifteen on the highway.

[360beast]

That's awful, running way too rich. I get very low 20's around town and on a decent long motorway run at least 30mpg.

Probably a worn out ECT.

[irishcarfan]

Generally get about 280-300 miles out of a tank on our B230FK

[Forrest]

I usually reckon about 24-26 mpg on average. Better on a long motorway run. That’s B230FK with automatic transmission.

The O2 sensor can lead to lower MPG. If it’s original it might be worth changing it.

[Mertz]

Low 20s around town. 28-32 on a clear run.

[Dirty Rooster]

When my odometer was working I got 31mpg, but I don't do short runs.
I assume I'm at 29-ish, might be rich, I'm thinking about getting a new water-temp-to-CPU sensor ...

If I had a "thing" that told me I'm getting 10mpg around town I'd rip everything apart to find the fault!

[baggy798]

You should be getting about 21 around town and 26-30 on a run.

Surprised it hasn't thrown a check engine light. Plugs are going to be getting fouled up and bores washed down.

[Chuck25624]

No check engine light, no codes. Going to change the O2 sensor this week.

[baggy798]

Do check the resistance of the engine coolant temp sensor like 360beast says. It's under the intake manifold runner number three.

From FAQ:

The resistance values between each of the pins on the sensor and ground, are (by eye from the chart):

32F (0C)-- about 6000 ohms within a range of +/- 10%
68F(20C) -- about 2300 ohms
104F(40C) -- about 1300 ohms
140F(60C) -- about 600 ohms
176F(80C) -- about 300 ohms
212F -- about 190 ohms

[bob12]

Originally Posted by baggy798

Do check the resistance of the engine coolant temp sensor like 360beast says. It's under the intake manifold runner number three.

From FAQ:

The resistance values between each of the pins on the sensor and ground, are (by eye from the chart):

32F (0C)-- about 6000 ohms within a range of +/- 10%
68F(20C) -- about 2300 ohms
104F(40C) -- about 1300 ohms
140F(60C) -- about 600 ohms
176F(80C) -- about 300 ohms
212F -- about 190 ohms

That's quite interesting as the quoted resistances ^^^^ are not unsurprisingly about the same for as those for the single dash coolant temp gauge (+ & - on the sensor and connector terminals).

As the 'back' sensor under No3'ish is dual with separate feeds for the ECU and the EZK with only + on the two sensor/connector terminals and - via the sensor body, I am thinking that by connecting a couple of 200 ohm resistors to the connector plug terminals and earthed separately to the engine/body, you could test the sensor/see what happens. Totally impractical though!

If it were me and I thought this sensor was past its useful lifespan I would just replace the sensor which ain't expensive.

Bob