Auto transmission with problems

[91SilForty]

Backstory thread: zerothread/201266

So tonight I took my multimeter out to the car and figured out the idle switch on the TPS wasn't engaging. I had adjusted the TPS to .5V, but I have to set it to .43V to get the closed throttle/idle switch to work. Fixed that, got diagnostics mode working again.

Here's the weird one: It no longer complains about the fluid temp sensor (yay), but it still complains about the TPS circuit. The TPS is brand new, bench tested good, and installed and adjusted right. WTF?

The symptoms now are:

1-2 is perfect, any amount of throttle, even at redline under full load. When it comes time for 3rd, it free revs. If you accelerate to redline in 2nd, then take your foot out of it, you can feel a slight kick when playing with the OD off button. The gears are still there, but they mostly just slip. I still think it's some sort of electrical problem though, because 3 and 4 were fine until they broke suddenly (profound I know).

Two questions:

Why is it still complaining about the TPS?

Can the solenoids get weak (bad ground?) and only allow the gear to partially engage?

Thanks for any help or advice.

[steve s14]

your tps is probably good but the tps circuit might be bad. maybe it might not be getting a 5volt reference or a weak ground. maybe the signal wire has high resistance or a bad connection. the transmission might be bad also causing the slipping in 3 and 4.if so, i have a transmission for sale! zer...01103

[91SilForty]

Alright, more screwing around has resulted in:

No diagnostic mode complaints! Woohoo!

When the idiot previous owner did the Silvia frontend, he never put the fender liners back in, so the grommet where the wiring enters the body has been blasted with water and dirt and crap and the connector between the ECU and the transmission brain seems to have oxidized slightly. Unplugging and testing continuity as per the FSM has resulted in complete communication between the transmission and engine again.

Bad news is 3/4 still slip badly, although I swear they're getting better as the recent fluid change flushes through. The car hasn't been getting driven much, so more regular useage may help.

At this point I'm thinking of throwing a bottle of Lucas transmission Fix in there. I've been reading all over the web and results seem to range between "Holy crap it works wonders" and "Not a miracle, but certainly helped." That's better than the typical 50/50 "swear by it"/"it exploded my car" in my mind.

Does anyone have any personal experiences with this product?

[hud240coupe]

Lucas helped my auto out a lot. I bought my 240 for real cheap with no reverse and 3 and 4 slipping. I had to nurse it till I parted together my 5 speed swap. I used lucas and 3 and 4 are good now. Drives great. Still reverse though.

[91SilForty]

Ok, well, we tried the Lucas Transmission Fix, and it did nothing, but I did realize something I forgot to mention before.

3rd and 4th don't hold acceleration at all, but they do hold engine braking just fine. Is this indicative of anything like a specific circuit not working?