Coolant Temperature Gauge Fluctuations?

Thank you very much for the reply. I already swapped the temperature sensor about a month ago and that didn’t fix the issue. I also confirmed resistance of the sensor and voltage at the connector. Regarding the cluster, I see the part isn’t that expensive, but it looks like a lot of work to replace it. A few questions, could it possibly be a loose or dirty connector? If so, is it accessible without removing the dash? Is the cluster just an output display, or does it influence the ECU and engine - air/fuel mixture? Note that when I have stalled and whenever there is hesitation, the temperature drop (especially below C when waiting at a light) often precedes hesitation and codes being triggered.

Note, I noticed that the visible ground connections to the body in the engine bay look pretty rusted. I also read that a bad ground somewhere can result in high resistance at the ECT sensor. Could it be that there is a bad ground that both the Fuel temperature sensor and ECT sensor have in common?

I checked for a good connection at the temp sensor and added a small drop of adhesive in the plastic part of the connector to help ensure it doesn’t move. But the issue is still present. Regarding the grounds... This is a new area for me. I was looking at the wiring diagram and figure I should start with the ground connections to the body for the E16 and F24 connectors, and also the battery ground? See attached. And what do I do exactly to clean up a ground? Use PB blaster and Deoxit, and sandpaper to improve the contact?

Thanks, this is helpful. I plan to clean up the Grounds Monday night. I’ll let you know how it goes.

I cleaned the grounds and I think that helped a little. It is a little hard to tell as the outside temperature has dropped about 15-20 degrees the past couple weeks here in NJ. I am only seeing codes about 1x per week, and it is only P0181 (no more P0183). I have only encountered hesitation/sudden drop in RPMs/temp a few times the past couple weeks, instead of it being frequent occurrence every day. This could be solely due to the cooler outside air temp though? My fuel economy is probably about 4 of 5 less (over the past few months) than the typical average for this car, which has over 289k miles. I changed the spark plugs (replacing the NGK laser iridium’s with 70k miles on them) and I think I am getting. About 1mpg more. I have a very basic scanner that provides fuel trims when a code is tripped and I noticed that with the last codes, the STFT was 25% (rich) and the LTFT was -4%. I am thinking my next steps will be to clean the throttle body (could explain running rich and hesitation?) And replace the fuel temperature sensor eventually.

Correction, LTFT seems to be correcting for a rich condition. The STFT might have compensated for a false cold fuel temperature reading?

Hi, the hesitation (jerking, threatening to stall) issue still occurs intermittently. I can drive for hours without issue, but then when the issues occurs, it is pretty severe. It tends to happen (sometimes) after being stopped at a red light and then accelerating (even lightly), especially when it is warm out. I changed the PCV valve and that didn’t really help. I used seafoam injector cleaner and my MPGs improved pretty significantly (by about 7MPG consistently), but this issue still occurs. Not sure if this helps but today, I accelerated pretty hard (didn’t floor it) and noticed that it started happening more during that acceleration (stumbled a few times maybe over 20-30mph) and continued to happen every time I accelerated from a stop during that drive... Then when I turned the car off and on, it seemed to go away.
I am thinking of cleaning the MAF and throttle body. What else can do this? I am also thinking it could be an O2 sensor or dirty fuel filter. Is there any methodical approach I can use to narrow this down?

Okay, thank you. I am considering replacing the cluster but want to understand its role a little better before I spend money on it. Could the cluster cause the drivability issues mentioned above, or does the cluster just serve as a display which doesn’t impact performance? When the temperature needle drops, the hesitation/stumbling occurs. It is not a separate issue.

All the grounds and battery connections are clean and tight. I purchased a Bluetooth dongle scanner (ANCEL BD200) last week but it doesn’t scan all the systems that you showed in your video. I will probably stop by an auto part store this week to have a CAN scan performed. However, I have observed some interesting things with my current scanner. I am thinking the temperature drop might be the least of my worries (or even just a symptom from the below issues that seem to happen simultaneously). I’m pretty sure I need to post a new question or 2 to handle some of the below. Please let me know how I should organize the question(s).
1. The first image shows an example of the temperature drop I have been talking about.
2. 2nd and 3rd images: After the car was idling for a while (waiting in line at a car wash on a warmer day), I noticed the LTFT was around +30% (wow). When I left the car wash, immediate stumbling/misfires and rapid temperature fluctuations occurred. I then paid a lot more attention to the LTFT and noticed that when the car stumbles/misfires and the temperature drops, the LTFT is typically in the +20s or higher. If I drive it for a while, or even turning off and on, the LTFT tends to settle back down to normal levels and the car runs very, very well.
3. I don’t have a pic but noticed after a rough patch of the issue (when the LTFT was 30%), the on-board monitoring test showed there were numerous misfires in multiple cylinders.
4. 4th image. Could the VVT sensor be bad/dirty and maybe that is causing all of this craziness? The idle sometimes feels rough (not always).

Thank you for your help with this complex issue.

The temperature data generally has some fluctuations (see below) but I believe it is roughly the same during periods where the LTFT is high and during periods when it is normal. My scanner doesn’t have an overlay feature, but I will work on collecting 2 temp charts, one from a normal period and one from height LTFT. When the temp drops (below “C”), it is only momentary (maybe a second) but occurs simultaneously with the misfires. Could the sudden temperature drop be the engine going into limp mode from a possible dirty/clogged VVT solenoid not responding properly during acceleration. Note this car has 293k miles, I always use synthetic, but have had a couple longer oil change intervals. Note, as mentioned earlier in this thread, I have seen codes P0181 and P0183 quite a bit, but only when it is warmer out. My original theory was that a false low temperature reading from the fuel temp sensor was resulting in more fuel to be added. But now I am also thinking a potentially dirty VVT solenoid could be a significant cause of the symptoms (rough idle, loss of power/misfires, stalling (rarely gets that bad).
I also noticed there is an ambient temperature pid, that typically shows a temp that is 20 degrees cooler than the outside air temp. Not sure if that has anything to do with it.

Thank you, but I would like to try to rule out other possibilities before doing something drastic like changing the ECM. Today I noticed that the STFT often jumps to 25% when the system goes into closed loop and LTFT has been hovering around 9%. There is also a P0101 code. I cleaned the MAF recently, so I know it is not dirty. I also noticed that the commanded evap purge% was 0% through about 3 hrs of driving. I’m going to check the evap purge valve tonight. I guess I should also be checking for leaks? Any suggestions? How can I tell if the MAF is bad?
Note, the ambient temperature has been correct the past few days, so the 20-degree difference I noticed previously might seem to be an isolated event.

Update, last night inspected the Evap purge solenoid by unplugging its connector and the hose to the canister to check for suction and there was none present. I also tried to blow through it and couldn’t. Surprisingly, I did not get a code tor the unplugged connector (after a few restarts) until I drove it to work today. Immediately upon getting the code (P0444 as well as P0101) the car seemed to go into limp mode as acceleration was very weak. I pulled over, cleared the codes and restarted the engine. After that, power was restored, and I noticed the commanded evap purge was fluctuating again (instead of zero). The code event seemed to “wake” up the evap functionality. After that, the LTFT was 0 and the STFT fluctuated roughly +-8 for the remainder of the drive (not bad).
So, I am thinking it is either the ECM as you suggested, the MAF or the MAF harness/connector, or even just a dirty throttle body (as I have seen in another forum that dirty throttle body is known to cause this p0101 and stalling with this generation of Sentras). I plan to clean the throttle body and do the relearn (only costs me a bottle of cleaner). Remaining questions:
1. If that doesn’t work, is there any relatively easy way to test if it is the ECM or MAF?
2. If I buy an ECM that is preprogrammed to my Vin, would it be plug and play, or would the keys have to be paired somehow?

Thank you for your assistance.