bluesuby Posted August 12, 2015 Share Posted August 12, 2015 Usually I like to change the oxygen sensors around 100,000 miles, but due to procrastination and no check engine light, and this is the first day in months when the weather is suitable. I changed the upstream sensor with hopes of better gas mileage. My car is a 2005 LGT wagon with 136k on the odometer. Can I expect any improvement in fuel economy? I have not done the downstream sensor for 2 reasons: If I got a check engine light I'd have to read codes to figure which went bad, and looking at the location of the downstream sensor, this looks like a job best done on ramps or a lift. I read the downstream sensor is really only telling you if there's an emissions problem, and if I had a problem the car would throw a code. The same article said the upstream sensor does all the work with the car's computer and helps preserve the catalytic converter (I tend to believe this simply by looking at the price of each). Should I be in a hurry to do the downstream sensor? The car seems to run smoothly and I haven't gone far enough to see fuel economy results. By the way, the replacement was done by turning the wheels right and opening the access door. Just be sure to spray the base of the old unit with PB Blaster or a similar product. It did come loose with the special socket and a 12" ratchet wrench. Link to comment Share on other sites More sharing options...
bluesuby Posted August 14, 2015 Author Share Posted August 14, 2015 Had my first opportunity today to take an extended drive and travel on roads free of traffic. On the butt dyno the car runs more smoothly and acceleration is stronger. If anyone has comments on what I might expect from fuel mileage, I'd appreciate hearing your comments. I bought a Denso from Rock Auto because they had a great price and the Denso comes with the correct wiring. I'm not afraid to get out the soldering iron, but I'm not sure that arrangement would hold up as well with the varied engine and weather exposures. Link to comment Share on other sites More sharing options...
bluesuby Posted August 18, 2015 Author Share Posted August 18, 2015 OK, here's my observations. The on-board readout for mileage is indicating an improvement of 1 to 1.5 mpg over what came before. Of course it's hard to call this scientific because of variations in the driving cycles, weather conditions etc. It may be quite some time to recover the cost of a new sensor, but I know that cel was going to light up this winter on the morning after a snowfall and when the forecast says daytime highs in the twenties for the next month. Link to comment Share on other sites More sharing options...
orndog Posted August 18, 2015 Share Posted August 18, 2015 Yeah, you replaced something before it failed, it will be hard to measure an improvement. I've changed a sensor before it was needed myself. Link to comment Share on other sites More sharing options...
bluesuby Posted August 18, 2015 Author Share Posted August 18, 2015 Yeah, you replaced something before it failed, it will be hard to measure an improvement. I've changed a sensor before it was needed myself. Perhaps the failure wasn't bad enough to throw a code, but I'm thinking the effectiveness has been degrading since new. If this one goes over 250,000 miles it was worth it. Link to comment Share on other sites More sharing options...
Perscitus Posted October 5, 2015 Share Posted October 5, 2015 With everything else the same (no other mechanical or electrical changes, same/similar gas, similar ambient conditions, etc.), you could have quantified it if you had logged a few SSM or OBDII params specific or directly related to the front sensor before/after the swap. For example: A/F Correction #1 (Short-term fuel trim; STFT) A/F Learning #1 (Long-term fuel trim; LTFT) A/F Sensor #1 (AFR or Lambda) A/F Sensor #1 Current A/F Sensor #1 Resistance A/F Heater Duty And with a ECU/ECM reset in-between, you could have captured some Learned Views showing the before/after A/F Learning #1 A-D range values after say 100-200 miles of driving with the new sensor vs the Learned View captured just before swapping it. Link to comment Share on other sites More sharing options...
NavyMan86 Posted October 27, 2015 Share Posted October 27, 2015 I'm throwing the P0420 code and also throwing the P0304 code. Cat bank 1 efficiency or something and cylinder 4 misfire. Pretty sure the 420 code is causing the 304 code since the engine itself, mechanically, runs smoothly. Might just change the spark plugs anyway? But it didn't feel as though it needs it. Thank god I found this. I found the Denso uppipe o2 sensor for three different prices from the denso site itself and two others. I don't trust the "OE style" sensors, priced at 63 and 54 dollars. The SubaruOnlineParts description isn't enough to get it. Think I'm just gonna go with RockAuto. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.