Alkorahil

both of these symptoms....sound like O2 sensor problems.

You dont have a check engine light (CEL) on from this?

http://www.phyzixautomotive.com/pro-fuel.html

Yep! That is correct. It runs in open loop when cold untill it warms up then goes to closed loop and the ECU starts taking readings and adjustig accordingly (about 5 mins or so usually as a good bench mark). This is why so many people say their vehicle starts fine then starts running like crud after it gets 'warmed up', one it goes to closed loop and starts reading from one or more bad sensors such as the engine coolant temperature sensor or O2 sensor and getting bad input it runs lowsy. I would also adda proper working fan clutch-something people dont always think about. I would agree!! All of mine have survived Texas summers for many years running the AC at full blast. The cooling system is relatively simple and straight forward. As stated if everything is working properly there shouldnt be any issues. A properly functioning radiator, good thermostat, a good radiator cap, proper coolant mixture that isnt years old, proper amount of coolant and good hoses are all that is needed. We stock that part..... 21200-V7206 THERMOSTAT R50 3.3L V6 10/95-05/01 $18.56 (list: $39.23)

Old school notes from Nissan: Pathfinder or V6 Truck "For extremely cold climates interchangie to P/N 23100-2B000 No other interchange of thermostats is recommended"

I have never run those on a truck, but I will say from personal experience they are GREAT on Toyota camrys and Nissan Altimas.

As a follow up turd-ness can also be from clogged catalytic converter or bad O2 sensor (which wont cause a CEL or ECU code).

Its all about having good timing! (seriously no pun intended)

500-600 is way too low...... If the ECU temp sensor doesnt help I would definately get a timing light and check your timing. Make sure to do it with the AC and all lights, fan, etc off and transmission in neutral. The distributor timing being off a few degrees could also cause low idle a turd-ness. Woudlnt hurt to replace the sensor AND check the timing.

I agree with trogdor. (I always recommend Rancho, ProComp or Bilstein) Procomp shoudl be a little softer but still last a log time Bilstein are the only other brand i would reccomend in this case but they will probaby be to firm for you as well.

I just realized this is a zombie thread! 5 years old.....I read the subject header and thought "oh no another seafoam thread!" On a serious seafoam note....we got a new product called Physix in about a month and a half ago. Takes two people to do the treatment. It isnt a dump in the fuel tank chemical and it feeds though the fuel induction through pressure not vacuum like many others I have seen. Now generally I consider most of this type stuff to be "snake oil." They did two demos for us on the product at work with two vehicles they got out back fromthe trade ins. They ran both vehicles before and after the treatment and there actually was a big difference in the smoothless at idle and under load. I may give it a try in teh near future on my truck to see how it does.

Yes I advise that to many of my customers when they inquire.

Yes I have seen this several times. people replace the coils or just one coil and the light does not go off or comes back on after a few days or even runs worse. They then replace with the real deal and it goes away. In short aftermarket coils can make the CEL come on. I will say though that I see this behavior on Maximas more than the others.

Withthe sudden loss of all electrical power and the descriptions you are giving you have blown one or more fusible links.

Grey is the inhibitor relay. Blue is the Park/Neutral relay

The relays in the corner are for the blower and the AC (AC closest to firewall) The silver box is the Dropping Resistor for the AT The other relay near the battery is the Auto Amp Relay

There is also a very small.(about 5 inch long) vacuum hose back by the firewall that connects from the back of the intake plenum to the fuel regulator. If you look real good from the driver side you can see it, or put your hand back there from the passenger side you can feel it. It is known to have frayed ends from heat and years and not draw a vacuum to the fuel pressure regulator. I have even seen them just fall off entirely.

He is supposed to come pick up some parts he ordered this week. I will ask him when I see him for you!

Yes, that how they were presented in Yon Olde Days.

AS I like to say, anything is possible with enough time and money. That engine was used in the R50 from 1996–1999. As stated above the engine mounts and tranny should bolt up. IF you can get the seriers of the transmission that was originally mounted to it that would be helpful information. IF it hasnt been pulled out of the donor vehicle yet I would get some measurements as well.

What is the production date? or the VIN?

You mention twice that it starts acting up 'after it warms up' and and 'about 10 miles'. I am thinking this may not be a transmission issue. This symptom has me thinking of the engine coolant sensor and the O2 sensor both of which start giving signals to the ECU after the vehicle warms up. I would start with the engine coolant sensor. When they go bad they will cause hell with the engine as the ECU doesnt know what to do. IT is a very simple to replace part and very important for the engine to run correctly and get good gas mileage and they do nee to eb reaplced from time to time. Many here can attest to this.

There is a guy around here who did that with his WD21. It actually looks good IMHO.

I agree with the others, with low power and backfire this defiantely sounds like a timing issue! Besides the timing belt which I would also defientely check as the others have said, you could have the distributor rotated too far advanced or retarted. You can check this with a timing light.

The R51 already has an external transmission cooler mounted on the front of the radiator behind the front grille. Looks just like a B&M trans cooler. Just reroute the hoses to bypass the radiator. The path for the oil lines goes trans->radiator->cooler->trans.