Hi everyone. I've recently been having trouble with my Protege, it's eating gas. Right now I've only gone 60kms around town, and there is more than a quarter tank used. The car runs very smooth, less than 110,000km on it. I have another Protege, (2000, SE, 1.6L) with 200,000km, which can get 125-175km on a quarter tank.

There are two codes coming up, one is P1170 and the other I can't remember the numbers, but it has something to do with the evaporation system. (Same code is appearing on the 2000 Protege as well)

After doing a lot of research, I figured I'd start with the front Oxygen sensor since most of my research pointed to that.

Anyways, I took a video of the voltage fluctuation from the front O2 sensor. Research says that during idle the voltage should be between 0.45-0.5v. On acceleration, it should go up to 0.9v, and on deceleration, down to 0.1v. When the car is OFF, the voltage from the oxygen sensor stays around 0.113v. The way this is jumping around almost tells me that it's not reading correctly, but I'm not 100% sure. I was hoping someone on this forum could help me figure out this gas guzzling problem.

Thanks in advanced,
Mike

Here is a link the video:
2001 Mazda Protege SE - Error code P1170 - Oxygen sensor problem? - YouTube

 

It is easy to blame the O2 sensors. But too often the messenger gets killed for the bad news.
I don't think that a bad O2 sensor can raise the fuel consumption that much. First check the basics: plugs, wires etc. Clean the MAF sensor, check the EGR system, look for vacuum leaks.
Your engine should improve a lot by doing that. If you then still get the P1170 the odds are that the sensor is bad.

 

Hi tanprotege... I already checked all the plugs and wires. The MAF sensor is clean and the engine sucks in air just fine. I don't have access to a shop or tools at this point in time, so checking the EGR valve is a bit difficult. No apparent vacuum leaks. But saying all that, wouldn't those issues cause the engine to run rough? I have to repeat, the engine runs VERY smooth. It's just a fuel consumption problem.

 

Sorry, brain freeze.

I wonder how you calculate the fuel consumption. Do you rely on the fuel gauge or do you top off the tank and take the reading from the pump?

Fuel gauges cheat. First they drop fast, then at 1/4 or so they drop really slow-and it varies from car to car. You have to take the readings at the pump to reduce your error.

Confirm your fuel consumption over 3 tanks full.
Meanwhile check the wheels for dragging brakes.

tan

 

I always check my consumption this way:

1. Fill up the tank to first click, reset odometer
2. Drive until gas light comes on
3. Fill up tank to first click, record miles and litres used to fill up the tank

I then divide number of liters by 4.5 (4.5 liters in a gallon) and multiply kilometers traveled by 0.62. Then I take the miles and divide it by the gallons of fuel used to fill the tank. I never drove this car for the last few months, but with my older Protege the mileage has been pretty consistant. Always between 34.9-35.6mpg (in town) and 46.1-47.9mpg (on highway).


This car on the other hand though (since my father has been driving it in my home town) this car has been getting 17-18mpg around town and 26-27mpg on the highway. He has been complaining of the mileage ever since a few months ago, when I was away.


As for dragging brakes, all brakes were done on the car when we bought it in August. Handbrake does stick sometimes in the cold, but quickly releases.

 

I would remove the O2 sensor and clean it if possible and then reinstall.

 

I've googled doing this, but most people say you're better off replacing it than cleaning it. When you clean it off you're really just removing the built up carbon from the outside cover of the sensor, and not the sensor itself.

I'm going to a parts store tomorrow to buy one, I'll post back with results within the next week or so (after gathering some gas usage data).

 

Thanks, revy. Your way of calculating fuel mileage is correct. Obviously, you are in Canada, because your gallons are supersized.

I had an issue with my brakes. It appeared that the e-brake had fully released but the actuator mechanisms inside the drums were sticking.
Make this check: drive it and let it coast to a stop without applying the brakes. Secure the car and get out to check the temperature of the brake drums and the front disks. Since you did not apply the brakes they should be cold. The disks always drag a little, but they should be warm only and both sides should have the same temp.

Thanks for reporting back.

 

I followed your instructions, and all brakes were cold. In fact, my back drums seem to not even be engaging at all. (found this out after braking hard a couple times) The front rotors took all the heat. I also have been having trouble with my handbrake, but that's another issue. (I'll keep this thread on the topic of mileage)

Thanks,
Mike

 

Sorry for the late response. I was traveling.

So far I was holding you back on the O2 sensors because they are costly. P1170 means:
HO2S Bank 1 Sensor 1 Circuit. You can check the sensors (Youtube, How to check an O2 sensor). And you can check the wires to and from the sensors prior to replacing them.
It is also possible that the exhaust system is partially obstructed. you would have to pressure check using a vacuum gauge. Look for a Youtube how-to.

Good luck