'95 KA24DE failing emissions, occasional stuttering

[ztCount2]

Hello!

I've been troubleshooting some odd behavior, and would appreciate some direction before I replace anything else.
The car is a 1995 240sx automatic w/ KA24DE @ 140,000mi. Mostly stock, other than an unknown brand air intake, apexi N1 exhaust, coilovers etc.

For a while it was running quite rich, exhibiting very aggressive pressure pops any time the revs dropped, getting poor gas mileage and being a general pig.
The car moved pretty decently above 3000rpm, at low speeds it accelerated slowly no matter the throttle position.
Emissions testing at this time showed very high hydrocarbons at low speed/idle.

Both o2 sensors were replaced, the missing crank sensor added, all fuel injectors replaced, fuel pressure regulator replaced, and several vacuum leaks fixed with new hoses.
This solved the richness, as far as I can tell. No more gas smell, much better mileage.
Acceleration may be slightly better, although still not very enthusiastic at low rpm.
Spinning the tires in the dry on smooth asphalt is unlikely without heavy side loading. Maybe that is normal for this base engine ?

The latest emissions test was aborted due to nearly constant pressure pops between ca. 2300 - 2700rpm, general unruliness, and the appearance of a check engine light.
On the drive back home from this test from there was one instance of hard acceleration which caused harsh stuttering/bogging, with seemingly random jumping of rpm.
This stuttering has happened a few times before, but it's difficult to reproduce. Maybe 1 in 50 WOT accelerations has this stuttering effect.

A quick look at the ECU showed code 12: air flow circuit meter.
The car idles slightly rough, every few cycles of the firing order includes a misfire / loping and slight shudder.
Removing the MAF plug smoothes the idle considerably, which suggests that the MAF is the culprit and needs replacing.
Agree?

I also cannot identify a few things, maybe you'll recognize them:

Taped to the MAF end of the harness, fuse/resistor on the end of it, looks like there was a shroud over it which is broken.


Same area, before the MAF branch.

[ztCount2]

Sorry for the doublepost, I don't see an edit button.

Forgot to mention that the temp gauge takes a long time to move, and maxes out around 1/3rd.
Not sure if a bad temp sensor would cause my issues, or if the gauge/connection is bad.
The previous owner swapped the auto gauge cluster for a manual one.

[SoundEfx]

I feel your pain because mine did almost the same thing.

First, change both your coolant temp sensors.
One is for the ecu and the other is for the gauge. It seems as if your gauge one is working, but their very cheap, so might as well get a new one.

Also, it seems as if the previous owner did some weird stuff, so undo it before buying a new maf.
Might as well bring the car back to stock to determine what exactly is wrong with it.