94 240 conv with AT shift problems

[speedgods13]

My 240 has this problem. It shift perfectly from 1st to 3rd gear. Now, when going on the freeway, it will only shift to 4th, when the transmission is cold. Once it warms up, it will only drive in 3rd. Another thing I noticed, is when it's cold, and I hop on the freeway, if I throttle lightly, it will switch to 4th. When warm this technique does not work. When it's warm, and I try to accelerate, it doesn't grab, and just revs from 2500-3500 rpms, going about 45mph. If I can't find a solution, i'm just going to do the 5 speed swap.

[angHELLic]

Hi guys just ran into a problem that i need help with - I have a auto 91 240, 120000 original km's, just had 5 bolt s14 brake upgrade : problem occured while pulling into my driveway, when in park it is impossible to shift into gear without the use of the shift release, drives fine in reverse, but when in D, 1, or 2 car barely moves forward...please help any advice would be greatly appreciated.

[kosh1986]

iv been having trouble with mine for a couple days now wont shift till around 3 grand rpms think on just doing a 5 speed swap also

[pktj21]

did you ever find out what was wrong because mine is doing the samething

[speedgods13]

I've just learned to deal with it, until I swap out the automatic to 5 speed.

[pktj21]

you still having issues or have you figured anything out?

[speedgods13]

Have not found a solution to it. Doing a 5 speed swap, and never buying an automatic 240 again, unless I have everything to to the 5 speed swap on hand.

[kc240guy]

My old vert had the stuck in first problem so I unplugged the rev sensor and it worked. Then a couple years later it started not going above 2nd most of the time. Since it was rusted all to hell anyway I got rid of it and now I have a rust free 5 speed coupe.

[tcjohn2]

Thanks to all who worked out the shift problem. My '93 convert started to do it when I pressure washed the engine. i unplugged the sensor & it shifted perfectly. You probably saved me a transmission rebuild.

[gtd65]

Our trusty (maybe not so much recently!) '95 240SX has been laid up for the past 6 months or so due to the brake pedal switch stopper disintegrating. Well I'm back over in Florida for the rest of the year and we finally got around to fixing that issue last night - what a PITA that job is

Well after fixing the brake light the CEL light came on (I've not had this checked yet) and I noticed that the car is very slow to upshift (it's an auto) to 2nd gear from 1st.

I'm hoping this is just because it's been sitting for a while and needs a bit of a run to sort things out, however, having read most of the information here - does this also apply to the S14?

[biggie]

Most everything should apply to S14. But with it sitting that long I would have done some maintenance, including a transmission fluild flush.

[gtd65]

Most everything should apply to S14. But with it sitting that long I would have done some maintenance, including a transmission fluild flush.

Well I took a trip up to Advance for a CEL diagnostic check, the error codes were as follows:

1. PO325 Knock Sensor / CKT Malfunction BNK / or Single Sensor.
2. PO/31 Gear 1 Ratio Incorrect
3. PO/32 Gear 2 Ratio Incorrect
4. PO/33 Gear 3 Ratio Incorrect

On the way up to the store the transmission was changing up more slowly than usual but it appeared things were getting better the closer I got to Advance

The guys at Advance had a look at the codes and reckoned the problem is more than likely due to the car sitting for a while and recommended using "Seafoam" and driving around for a while to see if the problem continues.

The CEL was cleared and so far it's not reappeared.

I've never actually done a fluid change on an auto box to date - there seems to be two schools of thought:

A..Change it per the manufacturers recommendations.
B..Never touch it at all

I've always gone with option B and other than this issue not had a problem.

Is it easy enough to do an auto-transmission fluid change or flush with minimal tools/equipment

[biggie]

To get everything out, I've always went to a dealer (or place that has a machine) that can flush it. I paid to have my Vert's AT flushed when I first got it, never had an issue out of it, still worked fine when I removed it.

[ROOFLESS]

im not sure if anyone still post on this thread but i figured i might as well ask hoping some one will have an answer for me. Like everyone alse with an auto 240 vert, mine has shifting issues. i bought the car out a junkyard, test drove before i bought and ran perfect, On my way home with it, it wouldn't shift in to second gear. So i explained my problem to the owner of the junkyard i bought the car from, good guy, and he gave me a used transmission free of charge. so i swaped the transmission in my drive way. long story short couple months later is now doing the same thing changed filter and oil, neutral saftey switch adjusted shift linkage, nuthing works. the other day i realized that when i accelerate fast but not aggressively from a stop it would shift hard in 2nd but drop back into first after like 5 sec, and sometimes it wouldnt shift into second at all and i would have to pull off the road shut the car off and back on or let off the gas until RPMS drop and slowly accel (works sumtimes). HELP!! please SUGGESTIONS?! OPINIONS?! SOLUTIONS?! need my DD workn again

[cmkelly]

The first transmission was probably fine, you just needed to follow the instructions on this thread and disconnect the rev sensor. Do you still have access to it? If not try the sensor disconnect.

[ROOFLESS]

no i dnt kinda wish i kept it but i was moving out of state at the time and i didnt have any space to bring it with me. i will try the sensor tomorro and hopefully thats the problem

[gtd65]

Well our S14 still suffers from this problem - I can work around it to an extent by changing the throttle position to "manipulate" the gear change but my GF just simply does not seem to understand the concept of doing this...

Can anybody point me in the direction of the location of the rev sensor on the S14?

[ROOFLESS]

i disconnected the rev senosr and drove it around the block on a cold engine and it shifts like butter, i honestly cant believe sumthing as minor as a sensor was causing such a headache but BIG THANKS to NISTECH and all those who contributed. i feel so much better know that i know the problem is gone

[cmkelly]

I imagine we've ALL felt exactly as you do right now. First the initial fear while driving, "crap, what's going on?" Next the fear of how much it's going to cost to repair. And finally the overall gratitude to all those contributors on this board that have gone before. Glad you're back in the saddle again!

[gtd65]

Can anybody clarify which sensor I should disconnect on my S14 then?

Please see pics below and numbering sequences provided for guidance.







I've only really got this weekend to try to sort this out, as I'm off to WA state at the end of next week... gonna be a bit cooler to say the least!!!

[gtd65]

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

[cmkelly]

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

[gtd65]

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!

[jonesbones]

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!

[biggie]

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

[jonesbones]

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.

[biggie]

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

[jonesbones]

How much do you think for a transmission? 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.

[biggie]

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

[jonesbones]

And the transmission comes with a sensor?