Call me crazy but I want to replace my o2 sensor even if my check engine light didn't come on. I think the sensors are old, anybody think if I made the replacement there is a possibility of better performance, fuel economy, and cleaner emissions?
replacing oxygen sensor for fun.... no CEL on but will car run better?
- Thread starter hhoang3
- Start date
If your car is passing the emission test with low numbers in each category changing the O2 sensors is just a waste of money. Now from previous experience you can have a bad O2 sensor and NOT have a check engine light (CEL). Check your emissions first and see.
Brad
Brad
As a ASE MT. I think that replacing o2 sensor's on a regular maintenance interval is not a bad idea. They see alot of heat and abuse and on some older OBD-1 cars the range of voltage for these to "set" a check engine light is larger.As the sensor ages, it becomes sluggish. Eventually it produces an unchanging signal or no signal at all. When this happens, the Check Engine Light may come on, and the engine may experience drivability problems caused by an overly rich fuel condition. Poor fuel economy, elevated CO and HC emissions, poor idle, and/or hesitation during acceleration are typical complaints.
Oh and keep all silicone related products far away from O2's. They are fairly sensative and anything with silicone will ruin a sensor.
Oh and keep all silicone related products far away from O2's. They are fairly sensative and anything with silicone will ruin a sensor.
John may be right. It may seem that a "new" sensor has to progressively get worse as time goes on, but where is the point where you could "feel" the difference? I had no CEL and thought my car ran great. Water in a plughole made the car run rich fouling the rear O2. I replaced it and now it seems I have better bottom end and a stronger pull throughout the RPM range. I am going to replace the front for the heck of it. BTW go to sparkplugs.com for genuine NGK direct replacement sensors. $300.00 for stock---$54.80 TMD @ sparkplugs.com
Steve
Steve
I'm not to sure if you could call it fun if you don't have to replace it... Just make sure you have a six point whatever since I'm sure yours are in there tight. Depending on how old your car is and how many miles and if the previous person that changed them out put anti sieze in there will determine if you get them out or not.
I'm just saying be careful is all.
Stephen
I'm just saying be careful is all.
Stephen
Once one sensor goes they will all begin to fail, one by one.
For the most part they are pretty easy to change however, replacing the front, pre-cat, up stream 02 sensor can be a real so and so. I was fortunate to have LarryB do that one for me.:smile:
For the most part they are pretty easy to change however, replacing the front, pre-cat, up stream 02 sensor can be a real so and so. I was fortunate to have LarryB do that one for me.:smile:
Go to your local auto parts store and borrow the O2 socket and wrench set for an easy replacement. I know it may suck but a little heat helps get stubborn sensors out. Remember not to contaminate the new sensor with anti-seize.
I recently replaced my Bank 2 Pre cat O2 sensor... it was a bit of a pain (those Honda engineers must have tiny hands), but certainly satisfying doing it myself and saving a lot of money (and having tools left over to boot!)
My CEL no longer lights up and the car runs great.
BTW all the sensors are the same - only the wires are different lengths. You could get the universal fit ones if you want to do a bit of soldering.
Good luck.
My CEL no longer lights up and the car runs great.
BTW all the sensors are the same - only the wires are different lengths. You could get the universal fit ones if you want to do a bit of soldering.
Good luck.
When I had headers installed at 55,000, I purchased 2 new OEM 02's {ouch}, but felt it was a good maintanance investment since they would have to come out anyway.
I recently failed smog.
The check eng light was not lit and there were no codes.
One of the O2 sensors was not working well.
I bought a scanner before making any changes.
http://www.scienceofspeed.com/products/engine_performance_products/Linear-Logic/ScanGaugeII/
The old sensors readings would not change much.
The sensors values were constantly changing as they should be.
http://www.scienceofspeed.com/products/engine_performance_products/NSX/NGK/NTK_O2_Sensors/
I have a 1995. I only replaced the Upstream sensors not the one's after the cats.
I believe the secondary sensors only function is to detect a bad cat.
My cat's were bad as well
The check eng light was not lit and there were no codes.
One of the O2 sensors was not working well.
I bought a scanner before making any changes.
http://www.scienceofspeed.com/products/engine_performance_products/Linear-Logic/ScanGaugeII/
The old sensors readings would not change much.
The sensors values were constantly changing as they should be.
http://www.scienceofspeed.com/products/engine_performance_products/NSX/NGK/NTK_O2_Sensors/
I have a 1995. I only replaced the Upstream sensors not the one's after the cats.
I believe the secondary sensors only function is to detect a bad cat.
My cat's were bad as well
Good advice, all of you answered my questions very throughly about oxygen sensors. Sometimes I feel the same about thermostats, they fail more often then they should.
If you would like to check if you are having performance issues from your 02 sensors, disconnect them. Once you get the CEL lit, take the car out. If the performance is much improved, then you know.
Regards,
LarryB
. Once you get the CEL lit, take the car out. If the performance is much improved, then you know.Regards,
LarryB
My car was hesitating at low rpms and I tried shorting the fuel pump resistor, that made the hesitation go away. But I also tried disconnecting the o2 sensors and the hesitation went away (cel came on, of course). So I decided to replaced the aged oxygen sensors since my fuel pump is a Walbro that’s not all that old. Now the car is laggy, but the “hesitation” is gone...but the throttle response is not good. I put on two new Bosch primary o2 sensors, no CELs. But something is definitely wrong! Do I need to reset the ecu when I replace the sensors?! I couldn’t find anything like my “laggy” issue, not sure how else to put it. I press the go pedal and it barely responds for a second or two and then it pulls hard like it should have immediately. Might be worth noting I tried to short the fuel pump resistor again for the last test drive and that didn’t help the situation at all.
If the primary O2 sensors were failing, the ECU might have been accumulating a lot of long term fuel trim as it attempted to bring the fuel mix to what the O2 sensors told it was the correct value. If the new sensors are working correctly, that long term fuel trim may be excessive. Short answer, I would be inclined to reset the ECU which erases the long term trim value which is stored in the ECU and starts the whole process of accumulating trim over again. If everything else is working correctly, this may fix your problem.
You didn't specify your model year. If you have an OBDII car you can use a good scanner to read both the short term and long term fuel trims. Once the engine is up to operating temperature, if the short term and long term fuel trims are small single digit percentage values with your new O2 sensors, then the O2 sensors are likely not your problem.
You didn't specify your model year. If you have an OBDII car you can use a good scanner to read both the short term and long term fuel trims. Once the engine is up to operating temperature, if the short term and long term fuel trims are small single digit percentage values with your new O2 sensors, then the O2 sensors are likely not your problem.
Short term trims are not stored in memory so resetting will do nothing to those numbers. Long term trims are stored in memory; but, if the long term trims are small numbers or zero, resetting just resets them to zero and is likely to have little effect. However, resetting can't hurt, costs 0$ so its worth a try to see what happens.
The short terms were between 43% and -30% or 43% and +30% and this is after the engine is at full operating temperature? Are those front and back numbers or are those the values that the front and back are bouncing between? Some oscillation in the short term trim values is normal. Short term of +43 to +30% are fairly high. If they persist at that high level it will eventually shift to long term values that are that high. Trim values that high suggest a fuel delivery problem. Either inadequate fuel pressure or clogged fuel injectors. If the short term trims are bouncing between +43% and -30%, that seems really extreme. Its not obvious to me what would cause that.
As a matter of interest, which O2 sensors did you replace? The primary sensors are the only ones that affect engine operation. The secondary snesors just monitor the operation of the cat converters and have no effect on engine operation.
The short terms were between 43% and -30% or 43% and +30% and this is after the engine is at full operating temperature? Are those front and back numbers or are those the values that the front and back are bouncing between? Some oscillation in the short term trim values is normal. Short term of +43 to +30% are fairly high. If they persist at that high level it will eventually shift to long term values that are that high. Trim values that high suggest a fuel delivery problem. Either inadequate fuel pressure or clogged fuel injectors. If the short term trims are bouncing between +43% and -30%, that seems really extreme. Its not obvious to me what would cause that.
As a matter of interest, which O2 sensors did you replace? The primary sensors are the only ones that affect engine operation. The secondary snesors just monitor the operation of the cat converters and have no effect on engine operation.
I replaced the primary sensors, fuel bank 1 was -30 and 2 was at 43, they did go to nearly zero but when I revved it they went back to those values (give or take a few %). It was warmed up and in closed loop mode according to the obd scanner. I’m sitting at work with the clock fuse out now, though it sounds like that won’t cure me! I suppose a fuel pressure gauge may be my next step.
The old sensors were very blackened, if that matters. I inspected a couple spark plugs last weekend and they looked ok as far as I could tell. The coil packs also looked good, I have had to replace those in the past due to water/rusty looking contacts.
The old sensors were very blackened, if that matters. I inspected a couple spark plugs last weekend and they looked ok as far as I could tell. The coil packs also looked good, I have had to replace those in the past due to water/rusty looking contacts.
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White balance can really mess with digital photos, so I can't be definitive in my diagnosis; but, those spark plug insulators look a little too much on the tan side which suggest that the engine might be running a little on the rich side. Those look like plugs from a nicely set up engine from the pre 3 way cat engines of the early 80s. Engines of the NSX vintage usually run at an AFR of 14.7:1 and the plugs tend to come out almost paper white. I am assuming that this is an OEM engine with the OEM heat range plugs since colder heat ranges can change the color of the insulator. If your old O2 sensors were blackened with sooty black stuff, that would tend to support the diagnosis of the insulator color suggesting the engine is running on the rich side. Did those spark plugs come out of bank 1 or bank 2 or one from each? If they both came out of bank 1 that would jive since the -30% trim is trying to reduce fuel to correct the AFR back to 14.7:1. If one or both came out of bank 2, I don't know what is going on unless negative trim means more fuel and positive trim less fuel (that would be odd).
I would still do the reset and drive around thing to see if the problem resolves itself. If the problem resolves itself, that would be nice. But, if you continue to run with significantly different trim values on the front and rear cylinders, that is a sign that something is not quite right. However, I am not sure what 'not quite right' would be. If the reset and drive around thing does not help, then I would be inclined to do a fuel pressure check and look at other things that could possibly cause the engine to run rich. I mentioned clogged injectors earlier; but, if you have an injector on 1 cylinder that is drooling a lot that can really screw up the whole fuel mix.
I would still do the reset and drive around thing to see if the problem resolves itself. If the problem resolves itself, that would be nice. But, if you continue to run with significantly different trim values on the front and rear cylinders, that is a sign that something is not quite right. However, I am not sure what 'not quite right' would be. If the reset and drive around thing does not help, then I would be inclined to do a fuel pressure check and look at other things that could possibly cause the engine to run rich. I mentioned clogged injectors earlier; but, if you have an injector on 1 cylinder that is drooling a lot that can really screw up the whole fuel mix.
Resetting the ecu actually made things worse, fortunately it was a short drive home. A little more background, I had experienced low speed hesitation but not so much low rpm until recently. Recently I started the car and it died a few times, so I replaced the main relay. Then the low rpm hesitation started. I have SoS headers, so all my O2 sensors plug in at the same spot behind the engine. I bought all four O2 sensors to replace, and the pair with the grommets (like the post cat ones on the car) had plugs for the front. So after I put them in I had to swap them out again. I also took out the cap and rubber seal from one of the connectors. All these things came together with me swapping the front and rear pre-cat oxygen sensors. Looking back on it, the trims were shouting that out at me I guess! Anyway, I disconnected one to confirm and then swapped them. All is well after a test drive this morning! I’ll get around to replacing the post car and the spark plugs shortly, but it looks like the main relay and oxygen sensors were failing at roughly the same time. Thanks for all the help, Old Guy!
And this didn't trigger any ECU error codes?
The factory sensors are made by Denso correct? Has anyone used the Denso O2 sensors for our cars from RockAuto?
I used Denso 02 sensors from rockauto recently in my 92. Cleared up the CEL and fluctuating idle that occurred briefly at warm up (can't explain why). The sensor wire was the correct length but didn't come with the rubber grommets that fit into the clips on the car. In retrospect I should have cut the rubber pieces off of the old 02 sensors and used rubber cement to attach them to the new ones. My part numbers are below.
| DENSO | 2344065 | |
| DENSO | 2344093 |
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