Auto harsh 1-2 shift

[g6civcx]

First, this is not my car. I'm helping someone else so don't say do a manual swap.

Second, I've searched every thread on Zilvia and NICO. If you know some better search terms to use then feel free to post. Otherwise, don't say do a search.


Car is an auto SOHC S13. When he first got the car, the transmission shifts really harsh in all gears, forward and reverse. It could chirp second gear with moderate throttle. Felt like dumping the clutch.

He took it to the dealer which drove it around the block and wanted $3,000 for a new transmission, quoting internal bearings failure.

He took it to a shop which checked the valve body, accumulators, and flushed the fluid. They said everything looked good.

Now all gears shift smoothly except for 1-2. 1-2 shifts is kinda jerky even with low throttle.

I drove it and it's not terrible, but he asked me to find out if it can be better.


I checked all the things people said to check.

The engine ECU throws code 55 which should be all clear. The auto ECU throws an intermittent code 3 = TPS. After I cleared the auto ECU memory and drove for a while, it doesn't throw any more codes.

I did a resistance check on the revolution sensor, line pressure dropping resistor, and TPS.

Rev sensor and dropping resistor came up to FSM specs.

The TPS came up 1000-8000 Ohms closed to WOT. People on NICO said that it should be 2-10. Could this be a problem?


I have not done a voltage check because the auto ECU is a little difficult to get to, but I will pull it and check out per the FSM.

Russ has said that it could be a torque converter on a similar thread, but I don't think this would cause harsh shifting in 1-2 only?


Any quick things to check before I go through everything in the FSM and do a voltage check?

[los_inc]

feed the trans some lucas no slip
it's a little thicker then trans fluid
it might help cushion the hard shifting
also check the condition of the trans mount
i hope this helps
-los

[g6civcx]

feed the trans some lucas no slip
it's a little thicker then trans fluid
it might help cushion the hard shifting

Are you sure about this? The problem is not that it's slipping. It's actually grabbing too much :)

check the condition of the trans mount

I'm sure the stock mount is toast, but would this cause harsh 1-2 shifts? I'll check it anyway.

Thanks for the suggestions.

[95KA-Turbo]

Is that little plug in the engine bay that is designed to make the transmission shift smoothly plugged in? On S14s it is on the driver side near the air intake box.

Simple as hell, but figured I'd ask just to be sure.




PS I have a S14 Auto tranny if you need a new one....I'm also in VA.

[Def]

Is the throttle cable tight?

Not sure if the S13s autotragic uses a second cable on the throttle pulley like some cars for some sort of shifting logic, but I used to make a quick $20 off people in high school by "doing a tune up" by hosing their engine bay out and tightening the throttle cable. It made every car shift better that had a second cable on the throttle pulley for the trans(mainly Hondas, but I recall my roommates Altima being the same).

[projectRDM]

There's no kickdown cable on the 240. The TPS being off would effect all gear changes I'd suspect, but it wouldn't hurt to adjust it a little and see if you get any results, either good or bad.

[AKADriver]

The 240SX doesn't have a physical kickdown cable. 95KA-Turbo, the plug you're talking about is the line pressure dropping resistor, the OP checked that. It was the first thing I thought of, too.

TPS out of spec seems pretty likely - can it be adjusted or does it need replacement?

[g6civcx]

Right, I pretty much checked all the easy things. The dropping resistor was 11 Ohms, which is between 8-12 as per FSM.

The secondary cable maybe the cruise control that you're talking about? This one doesn't have cruise so there's no secondary cable.

I'll try to see if I can adjust the TPS, but generally from what I've seen a bad TPS can't be fixed.

There's no kickdown cable on the 240. The TPS being off would effect all gear changes I'd suspect, but it wouldn't hurt to adjust it a little and see if you get any results, either good or bad.

I think you may be on to something. The car did get an idle adjustment at the shop so it may have softened up the shift a bit. I only feel the harsh shift in 1-2, but maybe the speed difference in high gear isn't so much so I can't feel it.

I'll check it out again. Thanks for reading.

[g6civcx]

Quick update. I checked with the technician yesterday and he said he adjusted the TPS to read .5-4.5V at the sensor.

I think that made the 1-2 shift much better than when it went in, but it's still not perfect.

I think the TPS needs to be replaced.

[g6civcx]

Quick bump with a couple of weird questions:


1) With the ignition key ON, when I turn the throttle, I hear a clicking noise in the engine bay area around the heater core. It's not audible from inside the car, only from the engine bay when I put my head near the heater core/passenger strut tower area.

The more I turn the throttle the faster the clicking becomes. What is it and is it supposed to do that?


2) I measured TPS voltage at the auto ECU and it's within FSM specs; however, the auto ECU is still throwing a code 3 = faulty TPS. I reset everything but the code still comes back.

I think the TPS needs to be replaced because I adjusted it the best I can. Voltage reading is right on with the FSM and there's no sticky spots. What gives?

3) It looks like someone has fooled with the transmission before because the factory seals looked out of place.

I did notice one very strange thing. In the SOHC FSM, there is a "lock up" solenoid, resistance = 2-5 Ohms. In the DOHC FSM, the same pin is called the torque coverter lock up solenoid, resistance 10-20 Ohms.

This is a pignose hatch = SOHC. When I measured the resistance on this pin and ground, it comes up 14 Ohms, which is spot on for the DE but too high for the E.

What gives? I checked everything and this is the only thing that was out of spec.

Could it be that the retard who rebuilt the transmission before used the solenoid from a DE and not an E? Could that be causing harsh shifting because the solenoid is partially locking?


This stuff is a nightmare. I hate diagnosing electrical stuff. Thanks for any advice.