idle/sputter/stall/fuel issues

[OPERATIONGINGER23]

I know this post is about a frontier, but it's the same motor as the 240s so here I am. So, recently I picked up a steal of a deal, or so I thought. Picked up a 1998 Nissan Frontier Ext. cab with 123k miles for $400. Not bad, right? Previous owner said one day getting off the interstate it started "skipping" and would cut off every so often. Motor is a ka24de 2.4L. So I took on the project. Brief rundown of the issues:

-Truck won't hold idle
-Truck sputters and chokes at low rpms and then stalls
-while driving, truck won't take throttle very well (try to floor it, and it bogs)

Upon much research, I've replaced the following things, each time in hope of making this investment worthwhile.

-mass air flow sensor
-throttle position sensor (even set it with multi-meter)
- coolant temperature sensor
-plugs
-wires
-distributor cap
-exhaust manifold
-o2 sensors
-cleaned throttle body

So I come to you all, in hopes of someone finding something I'm missing. I'm not completely blind to the mechanical world, but I'm no mechanic either. Any help or suggestions would be greatly appreciated.

[PapaSmurf2k3]

Realistically you need to determine if it's a fuel or ignition problem. Does your spark look really healthy?
Did you try resetting the Ecu after replacing all of those items?

[kevinfm91]

Is the truck completely stock or does it have some performance parts on it, exhaust, intake and what not.

[essfourteen]

Sounds like a vacuum leak.

[PapaSmurf2k3]

I was thinking of that too, but usually vacuum leaks are less and less prevalent with more throttle. The effect of the small vacuum leak becomes insignificant compared to the large amounts of air being sucked in through the throttle.

[centralcoaster33]

Vacuum is a good guess. I had similar issue. The hose from the PCV that goes to a vacuum manifold (that then goes to the intake manifold in four places) was exploded. My engine was sucking in air from past everything. Maybe check that area out? It's not easy, being burried inside the intake curl, but I could visually see the hose broken around the end of the PCV. The four other short hoses to the intake could also be bad, they're bent 90 degress and right next to the block, so they're pretty worn out after the years and could be broken. I replaced them all while in there for a knock sensor and EGR issues. Setting your idle and timing should happen with the new TPS and MAF in my opinion, but if it's running terrible, you can't really set those. Maybe take a look with the timing gun while you're working, at least making sure you're not way way off.

[Moto Man]

The fuel pressure regulator is another item to consider.

[The Inflicted]

Bad idle could be due to a dirty idle air control valve, especially if the problem only manifests itself when the engine warms up.
Trouble is, it's a b**** and a half to remove. One janky way to clean it is to find the intake hose leading to it off the main air intake and spray carb cleaner into it. An even riskier but possibly effective way is to pour a quantity of liquid fuel injector cleaner into that hose so that it runs to the valve and let it sit for several minutes. When you start the engine there will be an immense could of white smoke, but it worked for me.