Automatic Shifting Problem

[Mystikx]

Hello there,

Brief overview : I have only seen this problem once on this boards and it was not solved, give it another shot. I purchased a 93' SE coupe that had a shifting problem, figured i'd luck out and it would be an easy fix : WRONG.

The transmission shifts when it HAS too , not when it's supposed too. IT shifts at 6k revs everytime; no matter what gear. Now i went to the local mech and was told it was either speed sensor or solenoid , so to save money and tackle both cases i purchased another transmission that i knew WORKED, although the problem still occurs.

Now i than assumed perhaps it could be the speedo , it's a HUD and since i bought the car is had dimed in and out ; but i have seen it work. Therefore i'm going to give it a shot tom (i have analog) but i don't think it will solve my problem.

Although 5-speed swap has been in the back of my head the funds are not readily available at this time and basically want a daily driver .

What is fking wrong with my car... lol please help ...

[94_240sx]

You will have better luck if you post here since all 240 verts came only with AT.

[Mystikx]

Bump need this fixed!

[Felipe]

some how your car is not reading your RPM's right. so it dosent know when to shift.

[94_240sx]

Bump need this fixed!

Seriously, you'll get better response if you post here.

zerothread?id=96505

[Mystikx]

I think i may have found my problem Thanks 240 btw :

"It's the TPS. was throwing 2.68V at closed throttle as opposed to the 0.4 expected. Just got a replacement, gonna swap it in a little later, I'm tired as hell.Check the voltage on term 20 on the ECU (NOT atcu) to ground, see if it gives 0.4 at closed throttle and 4.0 at open and ranged in between. Sounds like you're having the same problem as me.And driving with the bad tps disconnected was fine. Obviously it shifted based on the charts in the fsm rather than pedal pressure, but otherwise performed beautifully."

This is quoted by someone who had the same problem, now i just wanted to confirm which part i need to disconnect. and its where-abouts

[Mystikx]

Update:

So i swapped my cluster over to analog , speed displays but does not fix my problem.

I also unplugged the TPS ; it would default and work if it was malfunctioning | It remains unplugged as im cleaning the contacts (GUNKY) but i doubt that will solve the problem.

Im pretty stumped at this point , could it be the speed sensor?I unplugged Rev sensor, no go ..

Im just frustrated and im not to fond of dropping money on a local mech , considering they have mis-diagnosed 2 times already ..

[Aaron D]

I don't know if this will help, but I had a buddy that had a '90 automatic with the same symptoms. He isolated the trouble to be a resistor on the drivers fender well, it was for the trans line pressure sensor. He replaced it and all was well with his car.

Might be something to look into.

[Mystikx]

Update :

Replaced the ATCU and looked into the Pressure Line Sensor ; i unplugged a resistor which was believed to be it .. located on the driver side fender.

Not to sure how to test it though .. im just learning lol

[Mystikx]

any last ideas? im heading to the transmission shop tomorrow just wanted to gather as many useful opinions as possible

[SsinnerR]

have you checked your transmission filter?

[Mystikx]

Im on my second transmission now lol ..

[Mystikx]

Perhaps this may help.

So earlier in the week i unplugged the Pressure Line Resistor? i think ..; drove around the block and didn't notice anything - plugged it back in after.

Than today went for a cruise around town and turning which i actually got it to shift . I would have to hold it at (ex. 3000rpms) for a couple seconds than it would shift , first gear seemed like a rough shift, than second gear went over smoothly.

Now i pulled over ; unplugged the Pressure Line Resistor(which is on the driver side wheel ) blew on it a couple times ( lol ) than connected again.

From there on in the problem than returned .. hmm could this be the problem ?

I'll take a picture of what i unplugged, wanted to confirm its the right one

[Aaron D]

Any word on if this was ever resolved?

I just did an engine swap into an auto and it wouldn't shift out of 1st, still don't know what it was (probably TPS sensor), but instead of the headache I just swapped to 5spd.

[Mystikx]

Ya it ended up being the TPS