Nissan Repair Questions? Ask a Mechanic for Answers ASAP
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If the problem only happens when going downhill then I would first suspect fuel starvation. The downhill attitude is most likely allowing the pickup in the tank to suck air, either due to a restricted inlet filter or physical damage to the pickup/pump.
If you completely fill the fuel tank does the problem go away?
Try and take note of the fuel level when it happens, if the problem is truly related to attitude then you should find it happens when fuel level is under 1/2 to 3/4 tank.
I thought the problem was intermittent?
Whatever the cause the problem is intermittent. That doesn't rule out or condemn any component.
Do you have a scan tool to monitor data?
If no fault codes are setting it's really going to take the ability to monitor data while the problem is happening, or data recording to be able to play the recording back and get an idea of what is going on. Noting whether it only happens when the fuel level is lower was a simple thing that could be done without testing. Try keeping the fuel level high and see if the problem goes away.