ahardb0dy Posted February 16, 2012 Share Posted February 16, 2012 My 94 PF with the new/used JDM engine smells like it's running rich, I haven't checked the mixture with the computer yet but have no codes, No idea how old the O2 sensor is and I know I should change it. Question, will the O2 sensor throw a code when it is wore out or only if their is a problem with the electrical? What most likely would cause engine to run rich? Would the O2 sensor be top on the list? I was also thinking one of the injectors may be leaking fuel as when I first start the truck it kind of stumbles, was thinking an injector may be dumping extra fuel causing it to stumble upon start up, what do you think? Either problem (O2 or injector) would cause less than our normal stellar MPG right? Thanks all. Link to comment Share on other sites More sharing options...
Nefarious Posted February 16, 2012 Share Posted February 16, 2012 Well how was it running with the old motor? Was it running rich then? Did you use your old 02 sensor? Are you sure you didn't miss any electrical connectors or grounds? Has it had any tune up? Did you do the spare plugs, and check the cap and rotor for corrosion when you put in the new motor? How is the fuel filter? Link to comment Share on other sites More sharing options...
ahardb0dy Posted February 16, 2012 Author Share Posted February 16, 2012 Well how was it running with the old motor? Was it running rich then? Did you use your old 02 sensor? Are you sure you didn't miss any electrical connectors or grounds? Has it had any tune up? Did you do the spare plugs, and check the cap and rotor for corrosion when you put in the new motor? How is the fuel filter? It wasn't running with the old motor, and my buudy I bought it from probably never did any thing to it, not much for preventative maint. don't know how it ran on old engine O2 sensor is in the exhaust pipe right? Same one is still in there I haven't replaced it yet I didn't install the engine and engine runs really good otherwise I replaced the plugs (NGK), air,fuel,PCV, oil and filter. Cap and rotor looked good did not replace yet. replaced fuel filter. Link to comment Share on other sites More sharing options...
5523Pathfinder Posted February 16, 2012 Share Posted February 16, 2012 if its running rich, the O2 sensor is seeing a lean condition, telling the computer to add more fuel. There could be a actual problem, or the O2 sensor hasnt completely given up. The O2 senor basicly measures how many times the engine goes lean to rich and back again. There is a specific number of times this should happen at a certian rmp. If you were to tap into the O2 wiring and measured its signal with a Occiliscope, you would watch the wave form move up and down. The other twist is that it has to hit a certian voltage for both the lean and rich cycle. If it doesnt, usually(cause our rigs are older) it will not throw a code. A electrical failure is what usually turns the light on. If it was me, I would look around the engine back for vacuum leaks. Intake ducting after the MAF is what you are concerned about. This may be from a vacuum hose off or split, or a gasket that is not sealing. Also, you may want to check timing and be 100% sure its correct. This would also cause some lean/rich issues. 1 Link to comment Share on other sites More sharing options...
ejin4499 Posted February 18, 2012 Share Posted February 18, 2012 My 94 PF with the new/used JDM engine smells like it's running rich, I haven't checked the mixture with the computer yet but have no codes, No idea how old the O2 sensor is and I know I should change it. Question, will the O2 sensor throw a code when it is wore out or only if their is a problem with the electrical? What most likely would cause engine to run rich? Would the O2 sensor be top on the list? I was also thinking one of the injectors may be leaking fuel as when I first start the truck it kind of stumbles, was thinking an injector may be dumping extra fuel causing it to stumble upon start up, what do you think? Either problem (O2 or injector) would cause less than our normal stellar MPG right? Thanks all. just for kicks disconnect the o2 sensor and see if it leans out or stays running rich. If it leans out there is your problem an $80 o2 sensor. If it stays running rich see if something is impeding air intake. Link to comment Share on other sites More sharing options...
wd21overland Posted February 18, 2012 Share Posted February 18, 2012 Remember if you need to test it the ecu has a built in O2 sensor test. http://www.nissanpathfinders.net/forum/index.php?showtopic=21 1 Link to comment Share on other sites More sharing options...
tmoore4512 Posted February 19, 2012 Share Posted February 19, 2012 if its running rich, the O2 sensor is seeing a lean condition, telling the computer to add more fuel. There could be a actual problem, or the O2 sensor hasnt completely given up. The O2 senor basicly measures how many times the engine goes lean to rich and back again. There is a specific number of times this should happen at a certian rmp. If you were to tap into the O2 wiring and measured its signal with a Occiliscope, you would watch the wave form move up and down. The other twist is that it has to hit a certian voltage for both the lean and rich cycle. If it doesnt, usually(cause our rigs are older) it will not throw a code. A electrical failure is what usually turns the light on. If it was me, I would look around the engine back for vacuum leaks. Intake ducting after the MAF is what you are concerned about. This may be from a vacuum hose off or split, or a gasket that is not sealing. Also, you may want to check timing and be 100% sure its correct. This would also cause some lean/rich issues. Great minds think alike I guess... I was going to mention almost to the T exactly what he had said... I had the same issue... replaced the sensor fixed the issue... (I did not have a code either... do the below first!) Remember if you need to test it the ecu has a built in O2 sensor test. http://npora.ipbhost...hp?showtopic=21 X2 Link to comment Share on other sites More sharing options...
ahardb0dy Posted February 19, 2012 Author Share Posted February 19, 2012 I'll see if I can get out there today, have to install an amp in my car and we have a birthday party going on here today, I want to check the mixture ratio on the ECU as well. Thanks Link to comment Share on other sites More sharing options...
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