OK then here is a summary of what I tried today:

FAIL

A. Drove the car as normal - when engaging DRIVE the car lurches into gear and will stay in 1st gear until approx 4000RPM and then shift into second gear - car needs to be driven over (at least) 40MPH before it will up-shift into any higher gears.
B. Disconnected sensors 1 through 3 (individually) and car drove with the same characteristics as item A above - so no effect noticed.
C. Disconnected sensor 4 and when putting car into DRIVE no hard shift observed (definite difference). Car drove as if in some sort of "economy mode" with little or no feeling of power at all - suspect this is a mode where a single higher gear is selected? Car did not up-shift at higher speeds and appeared to be driving in a mono-gear...

Edit: Forgot to mention that with sensor 4 disconnected I can select 1st gear and drive off and then push the selector to 2nd and it will up-shift but continuing to DRIVE does not engage a higher gear - perhaps the car is stuck in 2nd gear when disconnecting sensor 4 after all?

So...

Disconnecting sensor number 4 seems to be the one that applies for the S14 but doesn't help my problem out so far.

One thing that I noticed, despite driving only relatively short distances, the car appeared to be pretty hot under the hood, even although the temperature gauge was in the normal position?

Any ideas based on any/all of the above?

Cheers in advance

No clue on the S14 - are there any forums/posts that deal with that model that could be useful? Sorry.

Problem solved!

Well, despite not having a TPS error code (or obvious TPS problems) - the TPS was showing readings well out of tolerance for the car.

Just changed the TPS today - which is the second TPS the car has had since owning the vehicle - and now the gears are changing perfectly!

It's taken a while to get to the bottom of this but it was a very cheap and easy fix now that it's over!

NISTECH,
Eight years after you posted this solution to the transmission problem as being the revolution sensor, I was having the shift problems discussed here, showed this forum thread to my mechanic, and had him remove the sensor to see if it made a difference and my transmission shifts MUCH better. Now I am without the sensor and need to replace it. I don't even know if they still exist. Do you or does anyone here (if any of you are still members) know the part number of this revolution sensor (for a 1993 SX CV), or how I can find it? Any help would be greatly appreciated. Thanks!

One of my first stops is to search on courtesyparts.com for 240sx parts. But there may not be any left in stock anywhere.

Thanks, I'll try there.
Do you know if it's safe to drive without it long-term? It doesn't feel unsafe, but it does feel and sound a little different. I'm not a mechanic (I've just have had my pretty little red vert for 18 years for my everyday car and would hate to lose it.) so I don't know what else the sensor effects to know if I can drive it if a sensor is never found, or if it just takes awhile.

I wouldn't think it would hurt for a little while. And luckily AT S13 trannys would be cheap and easy to find I would think.

How much do you think for a tranny? Does a sensor come with it as part of the transmission or is there a chance I'd get another transmission and have problems again because of the sensor. Thanks for your help. I'm at a loss and I'm trying to keep my car.

AT should be free from someone doing a 5spd swap. Just search Craigslist or something.

And the tranny comes with a sensor?

Just depends on the person/place.

is there an easy way to separate the connectors without destroying them?

Just wanted to post in here to thank all of those involved on the revolution sensor fix! It was amazing to watch the collaboration on this one and it was great work from all! Also, thank you for the solution!

thanks y'all. This post should be stickied. Y'all saved me so much grief and mild depression. I did the rev sensor removal "2nd connector" shifted but not great studdered until I got up to speed <10mph but went into all the gears. Parked, replugged the connector and bam shifts like butter. This may be a temporary fix but now I know what to do in a pinch. I'm in your debt team. 93 hatch fyi