Hello fellow nico club members, back after rebuilding my wrecked pathfinder. So I have a few issues I need help solving.
1st issue is the fan clutch is always spinning at full speed from the second the car turns on to the second it turns is this normal? I dont like it, sounds like a semi coming down the road lol.
And the 2nd issue that's very worrisome to me, the RPMs seems to always be about 2000 while driving and never go above 3000, always shifts at 3000 and when I let go of the gas it drops to 1500-1000 rpms instantly not gradually. It can only go above 3000 if it is revved at a stand still. And this worries me because I have a feeling the motor is failing and this doesnt help.

Forgot to mention its also a 2004 SE Automatic

Your fan clutch is locked up. There is no fixing that so it must be replaced. As for the engine speed oddity, it sort of sounds like you're describing what the ECM does when it goes into fail-safe mode but that usually means the engine speed will be limited to 2400rpm or so as it forces a fuel supply. You need to attach a decent quality scan tool to the data link of your Pathfinder to see what is going on with your engine and read any DTC issues that are being flagged before you can even begin to figure this one out.

Thank you for the response. I have no check engine light, don't know if that's relevant or not. As for DTC codes, I've scanned the car and I get codes "1 INITIAL START" for transmission code and "P1564 ASCD SW" for the engine.

Edit: HO2S1 B1, B2 both are running rich

Not all DTCs will turn on the check engine light. No worries on the "1 INITIAL START" message. This is not a malfunction message (Whenever shutting off a power supply to the TCM, this message appears on the screen.) Refer to page AT-40 of the FSM https://www.nicoclub.com/service-manual ... 004/at.pdf
The P1564 DTC is a malfunction indication for your cruise control switch on your steering wheel. I'm not sure how this is related to your symptoms but it is tied in electrically to your transmission control module so that might be the cause of your problems. See pages EC-54-55 for a description of the ASCD system and pages EC-645-651 for a more detailed description of the P1564 fault. I don't know if fixing this would resolve your issue but it should be fixed nevertheless. https://www.nicoclub.com/service-manual ... 004/ec.pdf
As for the O2 sensors, they are a witness, so to speak, of what is happening with the air/fuel mix ratio. If they are showing a consistent low voltage (rich condition), that signal should be telling the ECM to reduce the injectors pulse width to lower the amount of fuel injected. Your long term fuel trim readings with the scan tool should be able to confirm that by a showing negative percentage value on both banks. Here again, this might all be related to improper signals the ECM is receiving from the TCM because the ASCD is putting out a bad signal.

Oh wow! That's a lot of good info there. Thank you l, will see what's up with the ASCD.
Sorry to bug you but one last thing, was driving tonight and got a new code P0420 for a catalytic converter (might explain the fuel smell, backfired twice and bad fuel economy) could this also cause the possible fail safe mode?

The P0420 code is a catalyst system efficiency below threshold issue with Bank 1 (passenger side). The ECM is looking at the upstream O2 sensor and expecting the downstream O2 sensor to be within a certain signal range but it's not. The rich condition you noted earlier is the scary part now because of the "backfire" events which are more likely to actually be fuel saturated in the catalytic converter that ignited. The scary part is that this can destroy a catalytic converter faster than you can think, 'what the hell was that'. Possible causes of P0420, are referenced on page EC-334 of the FSM. Of those causes referenced, my money is on leaky fuel injectors. If your long term fuel trim is indicating a negative percentage of anything more than -10% (I bet yours is more like -20% or more), but you're getting unmetered fuel so your O2 sensors see this rich condition, then I would say that confirms the infectors are leaking. However, a fuel pressure test would verify that without a doubt.

Ahh ok. Gonna have to look into it. Thanks for all the help!