Pathie4me Posted March 6, 2007 Share Posted March 6, 2007 I have a 98 3.3l pathfinder and it starts fine when cold but stall out when it warms up, there is no codes. Link to comment Share on other sites More sharing options...
nissandoms47 Posted March 6, 2007 Share Posted March 6, 2007 well any more details? like what happens when it stalls. RPM fluctuations? or just dies... Link to comment Share on other sites More sharing options...
Pathie4me Posted March 7, 2007 Author Share Posted March 7, 2007 all power is there it just stalls and wont start again untill it gets cold again. Link to comment Share on other sites More sharing options...
NismoSkyZ Posted March 7, 2007 Share Posted March 7, 2007 Plugs possibly? Link to comment Share on other sites More sharing options...
XPLORx4 Posted March 7, 2007 Share Posted March 7, 2007 Did this happen all of a sudden, or did you notice problems with drivability before this? If the engine doesn't give any signs that it's about to die before it quits (i.e. no rough idling, misfiring, lack of power, etc.), then it's possible that the engine coolant temperature sensor may be bad. High ECT values will trigger the PCM to shut off the engine. If the sensor is sending a voltage that's too high , the PCM will think the engine is overheating and will shut it down. You may not trip a check-engine light if the ECT sensor's voltage is high, but not out of spec. Check the resistance of the ECT sensor to see if it's bad (or if you have an OBDII scan tool, such as the Scan-Gauge, it can show the ECT.) Refer to page 116 for details. Link to comment Share on other sites More sharing options...
02silverpathy Posted March 7, 2007 Share Posted March 7, 2007 (edited) This part is about $24 from Advance or Autozone....I had a post about this moons ago...it gave my path some of its needed MPG back...I will see if I can find that! ********Shew that took forever!*********************** Old Azz Post Edited March 14, 2007 by 98silverpathy Link to comment Share on other sites More sharing options...
mora2818 Posted March 12, 2007 Share Posted March 12, 2007 So I replaced my Coolant Temp Sensor after I saw this post and noticed 3 more MPG on average with the first tank. What causes this drastic change? Link to comment Share on other sites More sharing options...
RWC5S2 Posted March 12, 2007 Share Posted March 12, 2007 What is the life span on these sensors? I just turned 50,000 on my 2003. Should I start looking for a new sensor? Link to comment Share on other sites More sharing options...
XPLORx4 Posted March 12, 2007 Share Posted March 12, 2007 (edited) So I replaced my Coolant Temp Sensor after I saw this post and noticed 3 more MPG on average with the first tank. What causes this drastic change? When the ECT is low, the PCM operates in open loop mode, which means instead of using the O2 sensors to monitor air-fuel ratio for optimum performance and fuel economy, it will use a pre-programmed fuel map. Typically this fuel map causes the engine to run a little rich. When the ECT reaches 154°F, the PCM switches to closed-loop mode and begins using the O2 sensors to regulate the fuel injectors. So, let's say for example that your ECT sensor reads too low by 30 degrees. The thermostat opens at 180°F, and the normal operating range of the engine is between 175-225 (needle stays in the middle), but if the ECT sensor reads only 150°F when the temp is really 180, the PCM may cycle back and forth between open and closed-loop, reducing your fuel economy. What is the life span on these sensors? I just turned 50,000 on my 2003. Should I start looking for a new sensor? Variable, I suppose. I have nearly 150K on my '97 and the sensor seems to be operating normally. Edited March 12, 2007 by XPLORx4 Link to comment Share on other sites More sharing options...
tmorgan4 Posted March 12, 2007 Share Posted March 12, 2007 (edited) So I replaced my Coolant Temp Sensor after I saw this post and noticed 3 more MPG on average with the first tank. What causes this drastic change? Did you have the code for a bad sensor or just wanted to replace it? Edited March 12, 2007 by tmorgan4 Link to comment Share on other sites More sharing options...
mora2818 Posted March 12, 2007 Share Posted March 12, 2007 No CEL thrown, just crappy gas mileage over the last 6 months. Figured $22 bucks was worth a shot. So far it should pay for it self very fast. Could O2 sensors cause a similiar issue with gas mileage if they are reading wrong thus causing switching back and forth between loops? And I should specifiy, could they read wrong and not throw a CEL? Link to comment Share on other sites More sharing options...
XPLORx4 Posted March 12, 2007 Share Posted March 12, 2007 The O2 sensor doesn't trigger the PCM to switch back and forth between open-loop and closed-loop. Once the engine is warmed up, the PCM operates in closed-loop mode. (I think it switches to open-loop under full throttle.) If the O2 sensors are bad, they'll likely thow a code, but replacing a sluggishly-responding sensor will improve economy as well as emissions. I found this article very informative about how O2 sensors work. Link to comment Share on other sites More sharing options...
02silverpathy Posted March 14, 2007 Share Posted March 14, 2007 XPLORx4 knows his sh** all right! I had a super AFC attached to my trucks ECU/PCM and it definately switched to open loop when in wide open throttle...I say this because the adjustments I made for the 70% throttle + made very little difference in where the wideband O2 sensor read....I had to make super drastic adjustments to see any difference, even then I am not sure how that worked (to show a difference). The truck even with a few bad injectors got its mixture dead on the money at 13.5 parts air/fuel at WOT. Awesome deduction Dean! I am not sure why certain sensors where out faster like the CT Sensor...all of us use coolant and most of us change our coolant...but my rig was neglected from its 1st bill of sale, so maybe when I changed it that was the first time it was done??? Link to comment Share on other sites More sharing options...
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