25 mpg

[resuwrecked]

Lol its just that like 3 other people said the same thing like it was new. But seriously. Just unplug it and drive normal for a tank. Injector cleaner is best used as a preventative maint. type thing, not so much for instant results, unless you use it in one of these to run it straight to the fuel rail under pressure

http://www.ntxtools.com/Merchant/graphics/00000001/str-tu-470a.gif

(disable the fuel pump and hook this device, pressurized by shop air)

[neanderpaul]

unplugged the O2 sensor. Ran a tank. 25 mpg. next?

[Pu241]

unplugged the O2 sensor. Ran a tank. 25 mpg. next?

Sounds like time for a new O2 sensor to me!

[neanderpaul]

Really? I'm sorry I'm an idiot. If it did the same mpg with the O2 plugged and unplugged I thought it would not be the O2 sensor. I'm being serious.

[Pu241]

Logic

No change in behavior when unplugging a "functioning" sensor attached.

Question then becomes is said sensor functioning?

Anyone know if an O2 sensor can be tested accurately with a multimeter?

[TominMO]

Really? I'm sorry I'm an idiot. If it did the same mpg with the O2 plugged and unplugged I thought it would not be the O2 sensor. I'm being serious.

If you were having a MPG-related problem, but with a known good O2 sensor, unplugging the sensor would only make the mileage worse IMO. So no difference implies to me that the O2 sensor is the issue, and you are running in the overly-rich "limp home" mode.

[neanderpaul]

Makes sense Tom. Thanks.

[Pu241]

^^^
Leave it to Tom to make what I thought was a concise explanation even more transparent to visible electromagnet energy!

[resuwrecked]

It would make sense that this means your O2 sensor is not bad. However, my experience with both the b3 and bp and a Wideband meter is that they run leaner with the sensor unplugged, both at idle and cruise. Thats from my experience with it.

Bad coolant temp sensor will make it run richer than its supposed to. I'd check the resistance with the engine hot and see how it compares to spec.

I still agree with euro that if you just go ahead and turbocharge the car the problem will be solved, lol.

[neanderpaul]

I don't know how to check resistance on either sensor. Any info there would be appreciated. Like settings on my voltmeter for instance. Is the coolant temp sensor the one plugged into the bottom of the rad? And as far as a turbo on the b3.... I have a b6t for this car. I have to finish my bp car before I get into this festiva. Obviously by the questions I'm asking I can't do these swaps myself. I am waiting for friends to help me.

[Pu241]

Coolant sensor is probably easily checked, might be something in trouble shooting manual on specs for it.

I disagree that the O2 sensor has been exonerated.
But, I'm also pretty sure you can't just check resistance or voltage output at ambient temps. I'll see if spec and or test procedure are in manuals.

Paul, you do have Festiva manuals don't you?

[neanderpaul]

Probably 3 if I can find them.

[TominMO]

Coolant sensor is probably easily checked, might be something in trouble shooting manual on specs for it.

I disagree that the O2 sensor has been exonerated.
But, I'm also pretty sure you can't just check resistance or voltage output at ambient temps. I'll see if spec and or test procedure are in manuals.

I agree with John's disagreement that the O2 sensor is not still suspect.

Since it's a simple one-wire sensor, you should be able to touch the + lead of your voltmeter to the sensor wire just above the sensor, with the - lead grounded on the motor. Set the voltmeter to 3 volts AC. If it is functioning properly, the sensor will read some low value as the motor is warming up, and then rise as the motor reaches operating temp. The range is .1 to .9 volts. The .9 volts indicates a rich mixture and .1 volts indicates lean mixture. When the motor is cold, the sensor produces no voltage until it gets sufficiently warm; it is in "open-loop" mode (probably running rich rather than lean, as a precaution). A broken O2 sensor will do the same thing. If the sensor doesn't reach .7 volts after warmup, the ECU gives a Code 15.

I got some of this info from page 6-10 in the Haynes manual.

[neanderpaul]

Good info. I'm going to see if I can find one of my manuals.

[neanderpaul]

I put the auto festy into a temporary retirement after I got cream puff. I pulled it out of retirement a few weeks ago. I replaced the 02 with a denso before the retirement. 25 mpg. I replaced the fuel pressure regulator. 25 mpg. I haven't replaced the plugs again yet. And I haven't replaced the coolant temp sensor. I will be after those next. Even with the festy sabbatical this is really REALLY old.