Fuelly Forums - 92 VX only getting 33mpg

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If youre compression is only 180, it is a little bit lower than stock. mine was hitting 195 in all cyls. If I were you I would probably just replace the o2 sensor. chances are it has over 60k on it. You could maybe ask the previous owner? It also takes some getting used to to learn how to drive the vx efficiently. Did you know that you can put around in town in 5th at 32 mph? Does your shift light work? You should gain at least 5 mpg with the lean burn installed.
Im at 56-57 MPH at 2,000 RPM, but I saw a picture of someone's vx that had even taller gearing than that, that was supposedly stock. Mine is a 94, I wonder if 92's had a different ratio?

I have a question. Maybe I missed something, but I am wondering if maybe the person who had this car, before you, may have dropped a different transmission into it. If you have the right transmission, you should be at around 2000 RPM, a 60 MPH. If you are running much more than that, then your transmission was probably swapped out and your going to need to change that back, to get to the mileage your expecting.

Right now, you seem to be getting more in the neighborhood of what I get with my 89 Wagon, which has essentially a DX drivetrain in it.

Quote:

Originally Posted by thewizard182 (Post 87732)

Checked the o2 sensor voltage from d14 to d16.
As far as i can tell it is the correct l1h1 sensor.

Until it warms up it's completely random, anywhere from -1.9 to +1.9
After it's warm it idles at +0.2 to +0.4
Under normal acceleration it goes from -0.4 to +0.7
When i accelerate and then let off the gas it goes to +1.9
Under hard acceleration it goes to -1.9
At 2k rpm and 60mph it goes between 0 and -0.4
If i let off the gas to the point where i'm losing speed it gets into the 0 to +.02 range

It's never very smooth of a reading, the only thing i can predict is the idle voltage, everything else jumps around alot.

It will go from 0.2 to -0.4 to 0.4 to -0.6 with each refresh of my meter, with as constant of a throttle as i can give it.

Does this seem right? I should be in the positive range at highway speed right?

I saw no one responded to this. So I thought I would. I'm not familiar with the pins on the car and why you have negative voltage, but normally an O2 sensor is something like 0-5V and 2.5V is normal. The lower the voltage the richer and the higher the leaner, so I bet your pins are just subtracting a reference voltage or something.

I bet negative is right and + if lean. So I'd say running a bit lean is normal for a lean burn engine and going heavy negative while accelerating is normal since I'm sure even the VX richens the mixture for acceleration. Going hard positive after letting off the gas is just a lean spike after acceleration. That all seems normal to me.

Now you can't really correlate voltage to specific A/F ratios, but I'd expect to see a bit higher than .2-.4 at cruise/idle in a good lean burn situation, maybe...

You should try reading these measurements again now that you have the correct plugs in.

Quote:

Originally Posted by Gary Palmer (Post 89194)

Transmission seems to be correct.

Quote:

Originally Posted by itjstagame (Post 89428)

This is after the correct plugs are already in. Yes, it does use a reference voltage, 0 being stoic, positive lean, negative rich. I am negative at cruising speed, I'm not sure if that is right as i have a california car. I started another thread with this specific question but it's not getting many replies either.

I swapped in the federal ecu and on my first tank got 49 mpg. My best tank before was 43 mpg.