I have a '95 Neon SOHC and the head gasket went on it, so I did the head gasket swap, however I forgot to change the oil, so eventually it started ticking, then knocking, and finally threw a rod over the course of like 2 weeks. I realized my mistake at the end, however when I finished the head gasket swap, the car developed a new problem. The car seemed to like redline at 2500rpm. You could ease the throttle up the rpms and get it higher, but when you just floored it, just rocked back and forward between 2000rpm and 2500rpm, sometime backfiring through the throttle body. Because you could ease it past 2500rpm, I was able to drive it around, but from a rest, if I "raced" it it would just lurch off like normal and surge at like 2500rpm, sometimes around 4k rpm. After it threw a rod, we took the motor out and sourced a '97 SOHC motor for it, we used the old motor's intake manifold and sensors, throttle body, transmission, and cam position sensor. We had the newer motor's coil pack, wires, and we bought brand new plugs and gapped them to .35" When we finally got the car put together, the same problem was still there. After writing this, I am thinking towards that the Cam position sensor may have gotten messed up, but what would it be? I ran the codes and I got code 12 and 24. I know 12 is the battery and I think 24 was the Throttle Position sensor. I tried cleaning the manifold with throttle body/carb cleaner but all it did was throw a foot of flame towards my face, so I took the hint along with the laughter across the street.

I haven't driven the car since I put the motor in, but it does start up nicely. During the removal of the engine, the transmission leaked, some fluid, so I don't want to try moving it yet. What type of fluid goes in a Manual transmission for a Neon and where/how?

I think 24 was the Throttle Position sensor.It could be your TPS or that it's disagreeing with your MAP sensor.

What type of fluid goes in a Manual transmission for a Neon and where/how?Make sure you use the A578-specific semi-synthetic fluid (p/n 4773167) that's available at the dealer. It is specifically matched to the synchronizer material for good shifting, and has special friction modifiers to last a lifetime...You're on your own if you decide to use something else.

I tried starting the car with the TPS unplugged, and the same problem remained, you still think it's the TPS?

Also, I have already added ATF+3 to the transmission made by Advance Auto Parts.

Also, I have already added ATF+3 to the transmission made by Advance Auto Parts.ATF stands for Automatic Transmisson Fluid...start saving up for a new tranny!

Well, I haven't driven it yet, so I'll drain it soon, so I have to get the dealer's fluid or is there a cheaper alternative?

Well, I haven't driven it yet, so I'll drain it soon, so I have to get the dealer's fluid or is there a cheaper alternative?Get the dealer fluid. Expensive, but worth it.

This is for the sensor problems, I had that problem on my neon. The sensors that where out were the TPS, 02 sensor, & 02 high voltage, which would adjust when U change the sensor.

My suggestion is that you get it check with an OBD computer that fits your cars application, "Thats How I Knew About Mines".

Been a while since a post, but I am still having a problem with the car. Since then, I have replace the throttle body and accompanying sensors(Idle Air, and TPS) and the MAP sensor, however, the problem has not stopped. The thing about the car seeming to redline at 2500 stopped with the replacement of the TPS. However I do not know what could be causing it. I am suspecting the coil pack, because we spliced a '97+ head onto my '95 harness and used a '97 coil pack, however, it wouldn't start until we reversed the two wires other than the black(ground I presume) wire. Then, for some reason it cranked and has been running ever since. Could that have caused a problem/is there a reason why that happened like that? I am out of ideas as of this message and I'm going to try and inspect the wires to the harness, otherwise I don't know.

Oh yeah, as far as the transmission fluid, I am using 70w-90 gear oil and have been driving it for a little. No problems yet.

I also have another problem that may not be related but... after driving the car around for longer than about 20 minutes I hear and see boiling in the reservoir. I am not sure why, but if any ideas, please help