pwb

Hi, replaced my O2 sensor and temperature dropped from 110-115 to 102-105 Celsius
Now it dont goes over 105 before i see drop beacuse thermostate open, on the old it could goes as high as 115 before it open.
Since the O2 sensor could have so much to say, what about other sensors?

dave1123

Have you recalculated your fuel mileage? Running hotter is usually an indication of a lean mixture. Usually a bad 02 sensor will make the engine run in "closed loop mode" meaning not controlling mixture by the sensors but by preprogrammed data from the chip. This is a richer mixture for warmup.

That's all I've got.

pwb

no, not yet. Replaced it yesterday so i will refill today to see if the fuel mileage is better. But the strange thing is that the temperature in front is the same, its the temperature where the sender is that is colder, but maybe the sender is so close to the exhoust that its possible that colder exhoust would lower the temperature on the sender?

pwb

The old O2 sensor is going up and down (0,2-0,6) and not over 0,6v when i test it with propane, its also going down slow after i remove the flame.

pwb

Another thing, it dont smells as hot as before outside the car, when stopping before i have had a hot smell on the passanger side, maybe some burned undercoating that was on the back on the exhoust tube, this smell is gone, so it must be running a litle colder i think. But need to use it some more to see if thats correct.

dave1123

I had a rethink. With the 02 not working, the rich mixture was still burning in the manifold and pipe and the convertor was running hot. Now it's back where it belongs.

One of the coolest things I ever saw was a Champion test spark plug made of clear glass. You could actually see the cylinder flame color and verify the mixture. This was about 40 years ago, however.

pwb

That make sense :-)

pwb

MPG before 13,5-14. After replacement of O2 sensor 15,5 or even higher :-)
The funny is that there wasnt any O2 error codes so replace a old O2 sensor could make some difference.

Would a correct air flow sensor and air intake temperature sensor do even better? I have cheap sensors, if i buy mopar sensors, could they make some difference?

dave1123

When vehicles first started being controlled by computers, there was a axiom used by techs, "If you're faced with a problem that you just can't trace down, replace the 02 sensor." I believe it's still true. One of the things some on this website do is relocate the IAT from the manifold to the intake system somewhere BEFORE the throttle body. It's supposed to improve power and smooth running. I don't know how it effects mpg. IMHO, the mpg you're getting now is about as good as it gets.

About replacing the sensors, Some aftermarket sensors are good, some aren't. With the kind of mileage you're getting now, I wouldn't replace any until you have further problems. Just my opinion.

pwb

ok, thanx.

Bustedback

A slow responding o2 won't usually set a code, especially on an OBDI vehicle. As long as the PCM sees that it's switching it will be happy. But a lazy o2 will cost you in fuel mileage and performance. You get what you pay for with o2 sensors, pay a little more for quality. A friend of mine bought some cheap sensors for his Chevy truck and it ended up costing 1500 bucks for new catalytic converters.