Check your fuel filter and pump. Disconnect the line at the injector rail. Son in law's 04 Xterra had been sitting for 8 years with fuel in the tank. I drained that formerly gasoline chemical substance with the replacement pump and Thought everything was good. I had the same exact issue that you're describing. Found I had even more debris that made it into the intake of the pump and all I could get was a spurt of gas and that was it.

 

Welcome to Club Frontier!!! Have you hooked up an OBD-II Code Reader to your truck's OBD-II Port? Are there any Diagnostic Trouble Codes recorded?? If it's not your fuel filter / pump, then it could be your distributor's gone bad - modules inside of it, that is.

Download a copy of the Nissan Factory Service Manual, (FSM) for your model year Frontier from any of of the attached three websites:

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Nissan Frontier repair manual free download PDF | Car Manuals Club

Nissan Frontier 2000 - 2019: repair manuals, wiring diagrams and owners manuals - more than 250 manuals for free download.

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Nissan Frontier repair manual free download PDF | Car Manuals Club

Nissan Frontier 2000 - 2019: repair manuals, wiring diagrams and owners manuals - more than 250 manuals for free download.

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Follow the procedures in the FSM to test & diagnose your distributor. If the modules inside are bad, you'll have to replace them or the entire distributor.
Hope this helps... Good Luck

 

The OBD-11 scanner lastly was reading the throttle pedal position sensor. My truck doesn't have a TPPS. Before that it read TPS and IAC. Which all have been replaced. Fuel pump was good. New fuel filter. How can I tell if the computer is bad.
Thanks to all that have replied

 

The OBD-11 scanner lastly was reading the throttle pedal position sensor. My truck doesn't have a TPPS. Before that it read TPS and IAC. Which all have been replaced. Fuel pump was good. New fuel filter. How can I tell if the computer is bad.
Thanks to all that have replied

Did it give a P-code though? Some scanners might generalize a parts fault, but the code is what actually matters here so you can do a proper look-up in the FSM (links provided by idlafie). You're correct in that it doesn't have a TPPS.

When you installed the TPS, did you "calibrate" it? The process is rather confusing, and I just fussed with it a few weeks back on my truck (98 2.4L). It had been either idling high, or idling poorly depending on engine temps (when warmed, it kept dipping down to near-stall RPM). I pulled the throttle body off and completely tore it down for cleaning (including the IACV solenoid and chamber). When I had it all back together, the TPS is what gave me the most grief.

The FSM describes a process for probing for resistance on two pins as you clock the sensor. Problem is that if I seemed to follow the FSM, it ultimately preloaded the sensor position which caused a constant high rev (around 2K RPM). To clarify, the TPS "sensor" is actually a combined throttle position switch and throttle position sensor. That is, it detects both the overall throttle position, plus a yes/no of the throttle is even opened. After not getting the results I needed when following the FSM, I resorted to something like this:

1. When you're looking at the sensor from the front of the truck, the left harness is the throttle position SWITCH (pins 4, 5, and 6; left to right) and right harness is the throttle position SENSOR (pins 1, 2, and 3).
2. Engine off, using a multimeter to probe pins 5 and 6, you're supposed to clock the sensor until you find the point in which the switch just barely detects when the throttle is opened a hair (by manually rotating the throttle cable drum on the back of the throttle body). Problem for me is that even though I find the sweet spot, I was somehow still putting tension on the sensor portion so that when the truck was started up, the ECU was being told by the sensor that the throttle was opened. What I believe happens is that if the ECU thinks the RPMs should be higher based on the TPS, it'll open the IACV to bring more air to raise RPMs (you'll know this is happening because the TB will make a much higher pitched vacuum sound while you have the air filter off).
3. Eventually what I resorted to doing instead was checking the sensor voltage (pins 2 & 3, engine running), which had somewhere around 2V when the TB was closed. FSM says the voltage is supposed to be 0.2-0.8V when closed, and 3.5-4.5V when open. So, I clocked the TPS to get the voltage back down. This brought the RPMs back down and somehow also kept the idle at a reasonable level.
4. However, step #3 didn't make sense because then it would mean the position switch would be out of whack. Well, what I eventually found out is that if you clocked the TPS just a hair too much counter-clockwise, that voltage level would actually spike back to 2V and still satisfy the switch position. That is, it'd go 1V --> 0.8V --> 0.5V --> 0.2V --> 2V as I clocked it. So, in essence you have to find a very sweet spot where the TPS reports that the throttle body switch is closed AND the position sensor voltage is 0.2V - 0.8V. You really need a multimeter for this, since adjusting the TPS left/right does not produce a linear result, and the engine/ECU reaction isn't very useful.

After that, I followed the FSM instructions to disconnect the sensor, clock the distributor to get the timing right (20°±2° BTDC). Mine still idles a little higher than I'd like (850RPM ± 50, though it used to idle around 750 for as long as I could recall), but the idle has smoothed out. There's also a idle adjustment screw on the TB near the IACV...it's a plastic screw that has a rather large slot. Tightening the screw is supposed to lower the RPM, but mine is maxed and won't go any lower.

Sorry for long post; hope it helps somehow.