overheating and stumbling

[Nissan370]

on my way home and noticed the car was idling high and stumbling some.

looked up at my oil temp and it was sitting around 230-240 high for the temps being only 40 deg.
i pull over and also notice my engine temp gauge is jumpping from cold to normal temp then back and forth again. some times just sitting on low as if the car is not warmed up.

i pop the hood and remove the coolant reserve cap slowly and its boiling.

i turn the car off let it set for a few and i walk to get some oil and coolant
may not have needed the oil but i used them both.

got home. and i am strongly thinking my thermastat is sticking.

any help thxs

[osbornsm]

Sorry to say, most of the forum will be able to diagnose your vehicle because you're so far off OEM. Stumbling @ high temperature is only initiated by the car @ 280F... your description of issues @ 240 should not cause this.

But then again, you're turbo'd and ECU'd... so i got nothin.

[SouthArk370Z]

Originally Posted by Nissan370

... engine temp gauge is jumpping from cold to normal temp then back and forth again. some times just sitting on low as if the car is not warmed up...

The ECM is probably seeing the reported water temperature jump from minimum to maximum. When it sees max, it cuts power. I'd check the water temp sensor and wiring first. See FSM (link in my sig) for more info.

[Nissan370]

well reason i was thinking stuck thermastat.
if the thermastat is stuck closed it blocks coolant from getting to the motor
that coolant becomes ineffective and the engine temps began to rise.
as i was driving for about 30min before i notice the car feeling funny.

and as soon as the engine temp gauge showed normal and sit there for a few the oil temp started dropping so.

the oil temp my have been alittle higher then that but when i started to look around it was sitting about 240

[SouthArk370Z]

It could be the 'stat but a bad 'stat will not usually cause fast fluctuations in temp - they tend to stick in one position or have a limited range of movement. The sensor is probably working properly some/most of the time but it only takes a blip to knock the ECU into self-preservation mode.

Edit: have you checked to make sure nothing is blocking the radiator?

[juld0zer]

Originally Posted by SouthArk370Z

The ECM is probably seeing the reported water temperature jump from minimum to maximum. When it sees max, it cuts power. I'd check the water temp sensor and wiring first. See FSM (link in my sig) for more info.

I'm putting my money on the coolant temp sensor or its wiring too.
If you're not too burly, take off the ornamental engine covers, climb up with your knees on the radiator core support (the flat hard part) and have a look down near the firewall. You will see a silver cast alloy pipe with a connector coming off it. The sensor has a blue plastic base so it's easy to see but hard to access.

My mate had a R58 mini cooper S which had a faulty coolant temp sensor, it went from sub zero to way over 100*c and kept cycling back and forth. It tricks the ecu to run the cold start map and also tricks the ecu to run the failsafe mode with fans on full blast and AC disabled on our cars. Stuck thermostat would never cause that quick of a fluctuation.

Fortunately, Nissan uses the same sensor on heaps of their cars so a second hand donor is in abundance. And heaps of aftermarket options. It's a denso sensor from memory and you will need a deep socket to remove/replace it.