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Oxygen sensor question

965 views 11 replies 5 participants last post by  Ignatz 
#1 ·
Has anyone replaced their Oxygen Sensor and noticed an improvement in performance? My '93 190E 2.3 still has the original 02 sensor.
 
#3 ·
I have my O2 sensor replaced twice (every 90K miles) in each case there was a very noticeable improvement in performance. I also measured the lambda readings and the cars behavior during driving conditions before and after the replacement. The car was reacting much quicker with the new O2 sensor. Acceleration was not smooth and after the change it is like new.

My car burns some oil about a quart every 500-800 miles so the oxygen sensor was completely covered with soot.

If I were you I would take it out and have a look. I'm shocked you are still on the first O2 sensor.
 
#4 ·
I replaced mine a long time ago, and no improvement. I think I was fighting a dirty injector and replacing the Oxygen sensor was part of my plan. I'm at 287K now and running great. Dumping a bottle of Techron in the gas tank every 2-3 months is part of my maintenance wackyness. Next month will start my 20th year of ownership. I'm starting to forget why I replaced things.
 
#5 ·
Thanks for the replies.
We bought our '93 2.3 new, and the maintenance booklet doesn't say when to replace the Oxygen Sensor. It only states to replace the California models at 60K. We are approaching 113,000 miles, and I was curious if I should replace it.

My SLK230 threw a P0141 code and I need to replace the downstream 02 sensor. I have an original type Bosch replacement.
 
#6 ·
As a datapoint I also purchased mine new back in 89 though. The dealership insisted on changing it at 90K miles back 15 years ago. I'm in California. It was part of a major tune-up, so I'm not sure if the sensor alone was responsible for the improvement.

You may have seen a post of mine about not being able to pass smog out here six months ago at 180K miles. I took the car to the dealer and they insisted the O2 sensor was fine, but I think they were wrong. They changed the injectors instead. The performance mildly improved but the smog readings got worse. Later the cat was changed with an aftermarket and it passed. The muffler shop said the first thing the dealer should have done was to change the O2 sensor, as it is the cheapest way to improve things. He has been in business for 40 years so I believe him. If the cat change did not fix the smog that was going to be the next thing to do, but it did so I did not change it right away. I kept the original cat and inspected it, it was coated with soot. Which is why it was not doing much to reduce emissions. It was also blocking airflow.

I got suspicious about the 02 sensor after what I witnessed in the cat. Pulled out the O2 sensor and sure enough it was also covered with soot.

I can not see the sensor working with so much soot on it.

So I changed the O2 sensor and felt that the car was more responsive after the change. Though, I must say, the thing that really made a difference for me was a few months later my EHA valve started leaking fuel and after I replaced that the car really started accelerating much smoother. I have a thread on that too. BTW, the EHA life appears to be only 90K miles too. Got that replaced twice in 180K miles.

So if you are after a performance improvement in acceleration, I would also consider the EHA replacement. Those are not cheap though, they run about $250 but very easy to change as a DIY.

Good luck.
 
#8 ·
My 92 2.3 runs a little leaner since changing the sensor. I have also read recommendations of changing it every 60k miles. Mine was at 125k, and figured it was either original or had 60K on it. Mine doesn't use/burn oil, but it was still pretty black, so I am guessing it was original.
My version was in the engine bay, not under the car, so it was easy to get to.

Fairly inexpensive preventative maintenance.

Good Luck.
 
#9 ·
Hamada, seems '93 (2.3) and '89(2.6) O2 sensors are different. My 89 has only one sensor and it is right before the main cat under the car. It connects from under the car under the floor carpeting.

I wonder if the 93's have a separate sensor for the EGR valve. 89's do not have an EGR valve.
 
#11 ·
I remember when I replaced it before on m 1993 2.3, it was just one sensor in the engine bay on the exhaust manifold and I could not find anyone under the car past the catalytic converter. I will take another look and let you know if I just have one or two sensors (up & downstream).
 
#10 ·
I installed the new downstream O2 sensor on my 2001 SLK230 today. I couldn't believe how clean the undercarriage is, the old sensor and wiring were very clean and easy to replace. I cleared the codes and no more check engine light.

Maybe I'll tackle the 190 next.

Thanks again for all of the replies.
 
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