First Gen (95) Neon problems

This car has about 360k miles on it, and it was parked years ago when a piece of broken clutch cable locked the engine up. I thought the engine was dead(I didnt realize it wasnt until after i pulled it out), so I replaced it with one from the junkyard with 60k miles on it. Before the engine problem, the car was almost undriveable due to wiring harness deterioration, so I replaced the underhood wiring harness with one from another 95. Its all put back together now and runs fine, but there are a couple of problems. 1, the gauge cluster works intermittently, along with the cooling fan, and turning the turn signals on and off sometimes changes what works and what doesn't. 2, it wont pass emissions testing due to high NOx, but it doesn't set any fault codes. I want to finish fixing it because its a really rare car (one of 15 built NYG ACR 4 door), and it runs and drives fine otherwise, but I'm not sure how to fix the last few problems.

The electrical issues sound like deteriorated grounds to me. The high NOx, I don't know.

Congrats on reviving an NYG ACR. I had a chance to buy one but it was a little rough for what they wanted for it. I loved my white one but always missed the chance for an NYG.

high NOx is from too-hot combustion chamber temps - lean mixture / over-advanced ignition.

The gauge cluster probably needs the pins where it connects to the wiring harness re-flowed. You basically just pull the cluster out and touch a hot soldering iron to each pin for a few moments.

Neons don't have adjustable timing, and there are no codes for lean mixture, I will swap the oxygen sensor and check for vaccum leaks again though.

The O2 sensor will auto-correct for vacuum leaks.

My guess is, the cat's dead. NOx diagnosis is really simple:

Is the engine running at the correct temp? (Hot makes NOx)

Does the EGR valve function correctly?

Is closed-loop fuel control functioning?

Is the ignition timing right?

Are the combustion chambers clean? (Excessive carbon raises compression and therefore NOx)

Is there the proper grade fuel in the car? (No, you can't run 87 in a car that specs 91 and expect it to pass emissions. Yes, I know it comes from the same nozzle.)

If you can answer yes to all of these... it's the cat.

Or, there's an even quicker test. Does it have a tiny $60 mufflershop cat on it? It's the cat. Those can fail NOx even when new.

I think its probably the cat too, it barely passed the last time it was running. The thing that sucks is that I live in california so its going to be ~$700 for a new cat

one of 15 built NYG ACR 4 door

Drool...

I just picked up my second 95 sedan (first was a Sport, this one is not. ) and im scheming on painting it NYG. Just got a job which is partially learning bodywork, so color me slightly excited.

This one doesnt look so good anymore (wonderful 90s mopar paint quality), its fun to drive though at least.

700$ for a catalyst? Damn, I had one done on my truck a few months ago for 180$ installed and passed with flying colors on my emissions. Go to a muffler shop or call around and find a cheaper catalyst. Even a catalyst for my my mercedes is 350$ installed so a neon should be closer to the pickup price.

Magnaflow 446265 is a direct fit calif. emissions for $270 on rockauto.

OBDII cats cost way more in Cali, $270 isn't bad though, my dad paid $600 for one in his legacy a few years ago, it looks like they have come down a lot.