Hodaka Rider Posted October 2, 2007 Share Posted October 2, 2007 On my '94 Loyale, should I get a code/CEL if I disconnect the Oxygen sensor? I was checking things over today, disconnected the sensor, and the idle did not change and I did not get a code. For some reason, I thought that strange. Link to comment Share on other sites More sharing options...
mikeshoup Posted October 2, 2007 Share Posted October 2, 2007 You won't get a code for a while. If you left it off for a certain number of minutes, you probably would. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted October 2, 2007 Share Posted October 2, 2007 The ECU won't react to it being disconnected right away. O2 sensors are interesting creatures - they don't begin "reporting" till they reach a specific high temperature. The ECU will not throw a code until it is unable to get a reading from the O2 for some specified amount of time, or possibly a specified number of start cycles. Depends entirely on the software of the ECU itself. It will not jump to conclusions about anything immediately - especially the O2 - unless it is in D-Check mode where it's internal test routines are much more stringent. Most ECU's I've seen won't pull an O2 code till you have driven 5 miles down the freeway, and NO single-wire O2 ecu will report an O2 code till the engine has reached operating temp and it kicks over to closed-loop operation. Till the engine warms it operates in open-loop mode where there is no O2 signal availible and it uses pre-determined fuel maps - ignoreing the O2 output entirely. GD Link to comment Share on other sites More sharing options...
Hodaka Rider Posted October 9, 2007 Author Share Posted October 9, 2007 OK, NOW I'm getting an O2 code. I spent most of yesterday doing brakes, axles (MWE FTW), and ball joints. Went for my brake bed-in loop through the countryside (lower speeds), and noticed my CEL on the highway on the way home (different route- highway speeds). Checked the code when I got home - 32. I have not done any further testing as yet. This is related to my previous thread input on hesitation/bogging/surging. (http://www.ultimatesubaru.org/forum/showthread.php?t=22047&page=4) I replaced the MAF and CTS to clear the codes mentioned in that thread. Next question: Has anyone known anything other than a bad O2 sensor to throw an O2 sensor code on an EA-82 SPFI car? Link to comment Share on other sites More sharing options...
Hodaka Rider Posted October 11, 2007 Author Share Posted October 11, 2007 OK, I'm thinking it may not be the sensor. I tested the O2 sensor: it's fluctuating between ~0v and 0.43 volts. Looks more like a lean condition than a bad sensor. Pulled a vac line after the t-body and voltage went down to a fairly steady .2-.3 - about what it should be. I may have mentioned before that my fuel pump seems to be a little noisy. Looks like it's time to check fuel pressure before and after filter and pressure regulator. Also need to check the wires at the pump for corrosion. Link to comment Share on other sites More sharing options...
mikeshoup Posted October 11, 2007 Share Posted October 11, 2007 Your O2 sensor should fluctuate between 0V and 1V. 0.45V on a narrowband is stoich. Your O2 sensor is bad. I've attached a graph of what the O2 sensor should be reading. Notice closer to 1 volt, the richer the mixture and closer to 0 volt the leaner the mixture. NOTE: In this graph, lambda represents the scaled ratio of air/fuel. 1.0 would be equivalent to 14.7:1. I don't think the lines are quite drawn straight on this graph as 450mV should be right at 1.0 Link to comment Share on other sites More sharing options...
Hodaka Rider Posted October 11, 2007 Author Share Posted October 11, 2007 I fixed my post - put a decimal in the wrong spot! Still think it's bad? It looks to me like it's just working really hard to compensate for a problem. Link to comment Share on other sites More sharing options...
mikeshoup Posted October 11, 2007 Share Posted October 11, 2007 Once the car is fully warmed up, depress the throttle a little. Does the voltage rapidly sweep between 0.2V and 0.7V? or there abouts? If not, then the O2 sensor is bad. You are backprobing the sensor right and leaving it connected to the computer, right? Link to comment Share on other sites More sharing options...
Hodaka Rider Posted October 11, 2007 Author Share Posted October 11, 2007 BTW: this testing was done with car fully warmed up (drove around town and came back, rad fan cycled during my testing) and I held the RPM's above 1200 for 2 minutes, as recommended in my service manual, before checking voltage. Rev up: Yeah, I'll try that tomorrow. Yes, backprobing with it connected. Link to comment Share on other sites More sharing options...
daeron Posted October 11, 2007 Share Posted October 11, 2007 check the voltage while you pull a spark plug wire. THAT will DEFINITELY cause rich exhaust fumes, and if that isnt above .5 volts then you need a new sensor. Just ask for the cheapest bosch-style single wire sensor; mine was a bosch piece and cost me 17 bucks. Link to comment Share on other sites More sharing options...
Hodaka Rider Posted October 13, 2007 Author Share Posted October 13, 2007 OK, tried the sparkplug wire disconnect - brilliant! Voltage did not change. Got a new O2 sensor - idle stabilized, revs smoother, but still a little surging. Back to the testing!! Link to comment Share on other sites More sharing options...
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