low miles per gallon

[BammBamm]

My 82 FI has been plenty of challenges. Now Im working out the last of them. The engine runs well with great power but I am only getting 25MPG. I also notice unburned fuel collecting on the back of the car. It seems like alot so I know it's running rich. Would exhaust sensor be the first place to start?

[RRoller123]

25 mpg is pretty normal for the FI. There have been a few threads on this. Mine runs an average of about 24 mpg, running around town and back roads with most of the time the pedal touching the floor or thereabouts.

[124JOE]

are you seeing a puddle out the exhaust?
thats not gas its water

[BammBamm]

Im seeing black sticky fuel coating the back if the car. I am familiar with that symptom being a rich fuel mixture.. It does sadden me that i will only be getting 25mpg.. Do carborated cars get better milage?

[RRoller123]

Can you post a pic of what is on the back of the car?

[124JOE]

ok run premium fuel for three tanks to help clean it out

[BammBamm]

It may to a week or so. I cleaned the car.

[BammBamm]

would changing the exhaust sensor help?

[wizard124]

If you break the sensor trying to remove it, you have created a bigger problem for yourself. That happened to me.

If it is working, you should be able to read VDC fluctuating with a multimeter. Do a search for procedures and readings.

[klweimer]

If you're not sure when you last replaced the sensor, replace the sensor. It's no worse that changing a spark plug. Under ideal condition, this sensor was to be replaced every 30,000 miles. Do you still have a catalytic converter? I'd be surprised if much raw gas is getting through there when it's warmed up. Unplug the oxygen sensor and read the voltage between the wire and ground with a digital volt meter. According to Mark Allison, the output should be around .45 with the engine holding at 2000 rpm. But as someone mentioned above, they jump all over the place when working correctly. Remember, 35 years ago, 25 mpg was pretty good; I think that's a pretty typical number. I don't believe the carb'ed units are any better. Most of the time, most of the carb'ed motors are less efficient than most of the FI motors (lots of generalization there )

[RRoller123]

If you break the sensor trying to remove it, you have created a bigger problem for yourself. That happened to me.

If it is working, you should be able to read VDC fluctuating with a multimeter. Do a search for procedures and readings.

I believe you should see an average voltage reading of about 0.4VDC and it will jump around. Exhaust needs to be fully heated, i.e. 2 or 3 fan cycles complete.

[bobplyler]

Do carborated cars get better milage?

No.

[silvadw]

I get around 30 mpg mixed driving on freeway and in suburbs. 34adf with no original California pollution stuff. I though FI would be better than that

[BammBamm]

I rebuilt my brake system and now Im getting almost 30mpg..

[klweimer]

You rebuilt your brakes twice? Shouldn't you get 60 MPG?
Seriously, what's really interesting is to T into the O2 sensor line while it's hooked up to the FI and then go for a drive and watch the O2 readings while driving under different conditions. Mine was consistently running lean (less than .45 volts), especially under acceleration. By loosening up the spring on the AFM by 4-5 teeth, I was able to bring that up to the .45 or a little higher during most operations. I will probably lean it out a bit bit before I go for the emission test.
Kirk