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1992 paseo
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Discussion Starter · #1 ·
I'll try to make this as short as possible for a long story. I have a '92 Paseo 1.5 5 speed. Around 200,000 miles started running rough, dead cylinder, turned out to be a total of 3 burnt exhaust valves. I replaced the burnt valves, hand lapped the rest, put new valve stem seals in, changed the oil. While I had the head off, I poured some of the Seafoam cleaner on top of the pistons as I have heard that the rings can get a lot of carbon built up on them. Car ran awesome but at the end of the 3rd day when I exited off the interstate the oil light flickered on. In 3 days it went through 3 quarts of oil. Only thing I came up with was I had used a hammer on top of the 11mm socket and lightly tapped the seals down instead of just pushing them into place by hand. So I tore it back down put in another new set of seals by hand only. Fired it back up sounds great still. But I noticed a lot of black smoke when I gave it gas. I checked the oxygen sensor and it was reading like it was fixed at zero ( 0 ). Easy enough fix, so I decided to take it to work and would pick up the sensor on my way home and replace it. It had a lot of black smoke, couldnt tell if there was blue though. But when I got home, the oil level had dropped about 1/2 a quart, and it smelled and felt like it had gas in it. Well I replaced the oxygen sensor and guess what... its STILL FIXED AT ZERO and still has black smoke on acceleration. What am I missing? I sure hope its simple and cheap, and hoping its not the computer. btw.. no check engine light on either. It has the two wire O2 sensor, and one side shows continuity to ground, and the other just shows open, and no sign of voltage. HELP! I dont even know if I solved my oil consumption problem either. The car runs too good and looks to good to give up on it yet.
 

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How are you testing the sensor?

Are you letting the car warm up enough?

The sensor has to be at 600 deg to operate.

The car should run fine without it even working though(like before warm up).It operates in open loop or defalt( programmed) setting. Even if you cut the wires to your ox sensor it would not cause the engine to run rich enough to put out black smoke.

Check your plugs for fouling, sounds like you have a stuck on injector. Listen to the injectors (with a large screwdriver, one end on the injector body and one on your ear )with the engine running( idle ) You should hear a steady clicking as the injectors open and close
 

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1992 paseo
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Discussion Starter · #4 ·
tested it using a DVOM. it just reads 0 volts. i let it get to operating temp still no change. up until i pulled the head, had no black or visible blue smoke. only used about 1/2 qt per 1,500 miles prior to pulling the head. my past experience tells me that even if its in open loop it should be fixed @ 0.4 volts or so until it goes into closed loop, not fixed @ 0
 

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1992 paseo
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Discussion Starter · #5 ·
did not change the rings, changed 3 valves, lapped them and put in new valve stem seals, which i re replaced and just pressed in by hand instead of lightly tapping with hammer
 

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There are different types of oxygen sensors.

Two of the most common are Zirconia and Titania.

Zirconia type( which is in my Tercel )also the most common, does not use a reference voltage from the ECU, but produces its own voltage( through an electrochemical reaction )depending on the amount of oxygen present in the exhast stream.

Titania type uses a reference voltage from the ECU, and its resistance changes( and the current it sends back to the ECU) depending on the oxygen present in the exhast stream.

So no, the sensor wont be fixed at any voltage once it gets up to temp,( at least 600f)the voltage will depend on the difference in the oxygen in the exhast stream and the ambiant oxygen. When up to operating temp( engine running) the sensor will swing between .1-.9 volts.Even when the ECM puts the system into open loop (like when accelerating) the sensor will still be putting out a voltage( changing) in direct relation to the oxygen levels.

Where you might see a steady voltage of .1-5 volts with the engine off( ignition on) is with a Titania sensor, because the ECU is putting it out as a referece voltage.

IF your sensor is up to operating temp( over 600f), and its putting out 0 volts, then its bad, but the zirconia sensor WILL put out 0volts until its up to temp.
 
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