Auto transmission with (surprise!) problems

[91SilForty]

Ok, first a brief history.

Car was purchased from a total ******** who beat the living hell out of the car, but, at the time everything worked. It's a 91 240SX. KA24DE, 4 Speed Auto, Silvia front end conversion, HICAS, Cruise, AC, i.e. pretty loaded.

P.O. Appears to have started a 5 speed swap but stopped halfway through. All wires going to transmission had been cut and then spliced back together. 1->2 shift was like a dumped clutch, other shifts weren't much better, but they worked. Car had strange hokey spliced in wire on TPS plug. And household wiring twist connectors on the ignition wires... but that's another story. At any rate, the car was driven for about 8 months without too many problems. In the space of about 2 weeks, the transmission stopped going into anything past 2nd gear.

At this point another car fell into the lap of the owner (my roommate) and the 240 sat for a couple months before I got back to school from the summer. I like to tinker with cars when I'm bored, and his cars usually are, so it works out pretty well. I got sick of looking at it out in the street, so I started tinkering with it.

First, I ran the diagnostic mode, and got trouble codes for the fluid temp sensor and the TPS. TPS was a big duh, so I replaced that. That fixed the dumped clutch syndrome on the 1-2 shift, and throttle response. Still no 3rd gear. Tried unplugging the revolution sensor, no change. Changed (not flushed) transmission fluid and filter. No change. Adjusted inhibitor switch (didn't check to see if it actually works, just adjusted as per the FSM). No change.

Here's the weird one. After I replaced the TPS, it stopped doing diagnostics mode. The light still comes on when it should during normal driving, but it won't go into diagnostics mode. I've checked the transmission computer visually (looks fine). The only thing that changed when it stopped working was changing the TPS.

Basically 1-2 is perfect, 2 disengages when it should shift to three, and then it just free revs. At that point it often won't go back into 2nd unless you move the gear selector. Before the problem, the transmission felt plenty strong, so I still think it's an electrical problem. I've checked all the fuses.

Any ideas are welcome.

Thanks

[91SilForty]

*BUMP*

Really the biggest problem as I see it now is the fact that diagnostics mode doesn't work. Can anyone point me in the right direction?

Thanks

[dickie]

wish i could be of more help, have you tried posting in the 240sx tech section? nistech should know a thing or two that could help you...

any reason youd be opposed to finishing the 5 speed swap, and curing the problems in the process?

[karmakaze]

wish i could be of more help, have you tried posting in the 240sx tech section? nistech should know a thing or two that could help you...

any reason youd be opposed to finishing the 5 speed swap, and curing the problems in the process?

thats what i would sugest.

[91SilForty]

Unfortunately, it's a matter of time, money, tools, skill, and it's not my car. Tech section you say? Darn... I thought I did post there. Whoops.

Can the mods move this thread for me or should I start a new one over there?

[dickie]

just start a new one, i wont tell anybody

[moyea]

Without seeing the car I would definitely focus my attention on the A/T wire harness. But make sure to check the fluid, duh. A flush may be in order.

Bust out the Voltmeter and get ready to jack up the car.

Check: You pretty much covered most of it.

Revolution sensor, Throttle sensor, solenoid switch, inhibitor switch, dropping resistor, TCU and TCU wire harness, basically everything listed in the FSM.

Look closely at the wires going into the transmission itself, the inhibitor switch, and recheck the TPS. Make sure it really is working. With electrical problems you have to be thorough.

If all else fails you can always pull the wire harness from the junkyard.

[91SilForty]

Well, started a new thread: zerothread/202825

Played with it more, got diagnostics working again. Follow above link for full story. Thanks for the help
Modified by 91SilForty at 8:38 PM 10/11/2006