'93 Impreza Auto Transmission Issue

[jj421]

Well, my $300 Impreza has hit the road, and I've noticed some transmission issues. It's a 1993, automatic, 4-speed, AWD.

 

When I got the car, it had a bad radiator. Because of this, I did not drive it much, but I didn't notice any shifting issues. I replaced the radiator, and in turn lost some ATF through the cooler lines. And now it's acting a bit funky.

 

When I start the car, the "POWER" light blinks. Then I start driving, and it doesn't shift into second gear until I reach about 4000 RPM, no matter how gentle I am on the throttle. The shift into second is quite rough, as it sorta lurches forward. Then sometimes when it goes into third, it hangs for a second before it actually catches. Every now and again, it won't go into gear, and the engine just freely revs like it's in neutral. Usually if I coast for about 3-4 seconds, it'll go into gear. Shifting into fourth, as well as downshifting, acts normal.

 

I've done research for the past 24 hours, but haven't found an answer. There have been two or three threads with similar problems like mine, but they were not conclusive.

 

I read the TCU code, and it comes up with code 31 for the throttle position sensor. I have tested the TPS to what I think is correct. The Chilton manual says to measure resistance between pin 2 and 3, which should be 13k ohm - 5k ohm (closed - wide-open). Mine measures 5k ohm - 1k ohm (closed - wide-open). No dead spots or anything. I tried adjusting the TPS, but the only thing it did was set off the check engine light. The resistances didn't change much.

 

I back probed the TPS and measured the voltage. The power pin had a solid 5.15 volts, the ground pin had a solid ground, and the center pin successfully swept from 0.5 to 4.5 volts (from throttle closed to open). From what I've been reading, that's correct.

 

I pulled the fuse for the TCU to reset it. Had the fuse out for about two hours, then put it in and went for a drive. At first start, the power light did not blink. But it still shifted the same way. Now the power light blinks for the same code.

 

I've read that you can unplug the TCU which should lock it in third gear, but I wanted confirmation as to where the TCU is. Under the dash, I suppose.

 

Also, in terms of ATF, it's clear. Like, I mean clear. When I undid the ATF cooler lines, red fluid came out. I topped it off with new ATF, but it's clear on the dipstick (very hard to see the fluid). The dipstick is wet up to the full mark, and when I wipe it on a paper towel, it has a pinkish hue to it. I have receipts for a transmission flush about 15,000 miles ago (last October).

 

Just went for another drive, and found that manually shifting through the gears works better. The 1-2 shift is not as rough and going from 2-3 still hangs a bit, but not as bad.

 

So yeah, any advice as to what is wrong? I would like to get this fixed, as I'll be getting the registration soon. Thanks!

Edited August 14, 2014 by jj421

[johnceggleston]

do you still have the TPS trouble light?

fix this first.

if the trans does not know where the throttle is , it will shift funny.

 

are you checking the trans dip stick?

how long is the dip stick?

where is it?

 

i think the TCU is under the dash, it is on the 95 - 99 legos.

[jj421]

Yeah, I was going to go to the junkyard to grab another TPS. I just wanted confirmation because from my testing, the TPS seems to have checked out fine. Besides the resistance values, but I may have done those wrong (or the Chilton manual could be wrong).

 

Yes, I'm checking the transmission dipstick. Dipstick is pretty long, on the driver's side. I know there are two dipsticks, one for the front diff fluid and one for the transmission. Owner's manual says the driver side dipstick is the transmission fluid.

 

So I just went out to the car to read the codes again. I believe you're supposed to warm up the car before testing, but I tested them cold. No active codes, but there were two stored codes. Code 31 and 32 were stored. These are, of course, for TPS and VSS1. The VSS code is new, and this is annoying because all the threads I've found online have had these two codes. But they never posted what they did to fix the problem.

 

I'm thinking, could the TCU be bad? I read that replacing the TCU fixed a different transmission issue on another site. The ECU is reading the TPS and VSS just fine. No stalling issues, no throttle dead spots, no speedometer error, no check engine light. So why would the TCU see those as faulty?

Edited August 14, 2014 by jj421

[johnceggleston]

 

I'm thinking, could the TCU be bad?

it is pretty rare but possible.

you can pull it and look at the circuit board.

there have cases where a bad TCU caused torque bind.

the guy said the circuit board was scorched.

 

i forget, have you traced the wires and looked for cuts,

abrasions,

or rodent chew marks?

 

code 32 is for the VSS1, which is on the rear trasfer case of the trans.

i have NEVER heard of one of these going bad.

(the front speed sensor, VSS2 can and will fail.)

so i'm thinking this is a wiring issue, or a communication issue.

the TCU would be a good place to start.

 

somewhere there is a pinout for the 95 TCU.

probably others.

[jj421]

Thanks for reminding me to check the wiring. I've been screwed over by wiring before. The immediate wiring connected to the TPS seems to be fine. But if that wiring was damaged, I would think the ECU would see it as faulty too. So it's gotta be TCU wiring.

 

I do not have torque bind of any kind, so yeah.

 

This morning I had to move the Impreza to leave for work, and the power light did not flash. I don't know why not, seeing as the only thing I did since I last started it was measure the TPS voltage. Yeah, to me it sounds like a wiring issue, especially if it's intermittent like this. I'll be at WCSS this weekend, but when I get back, I'll check out the wiring.

[johnceggleston]

the flashing ''power'' light, 90 - 94 , is a trouble indicator light.

it menas there was an electrical issue with the trans the last time you drove the car.

if you start the car and do not drive it,

the power light will not, may not, flash the next time you start it.

 

try it when you get home tonight.

park in the drive way and turn off the car.

then restart it, look for the flash, do not shift out of P.

turn it off and then start it again.

look for the flash, not there?

 

if it is a wiring problem, it will be after the TPS signal wire goes to the ECU,

but before the TPS signal wire gets to the TCU,

or it will be in the TCU.

 

i have a wiring diagram for a 92 liberty, australian legacy.

it may not be exactly the same as your 93 impreza, but probably close enough for it to help.

and the pins on the TCU are almost guaranteed to be the same.

 

 email me at ''canubaru at gmail dot com'' i'll send it.

Edited August 15, 2014 by johnceggleston

[jj421]

When I moved the car this morning, the power light did not flash. So yeah, because I did not drive the car, the TCU did not sense a fault. I would love to take a look at the wiring diagram; I'll send you an email now.

[jj421]

Okay, well I got home from WCSS and I'm a bit annoyed. Now it's working fine. Transmission shifts fine after the car sat for the weekend.

 

I started it up and moved it in my driveway. Power light did not flash (didn't think it would), then I parked it. Waited a while, and took it for a very short drive (about 3 minutes). Shifted normally. Came home and I downloaded your wiring diagram (thanks for that!) and went out to the car. I'm still not sure where exactly the TCU is. I pulled the panel off under the steering wheel, and was presented with this.

 

 

I'm guessing the "JC" box is the TCU. I could be wrong, but I don't think an ECU would only have two plugs. And from what I've been reading, the ECU is on the passenger. That being said, anybody who's done an EJ swap should correct me on that. But yeah, I took a look at this box, but didn't really see any frayed wires or obvious connection issues. I did see this though on one of the wires:

 

 

It was hiding under some electrical tape. Does not look factory, but it was well done. The wires were tight, but I crimped them even tighter to be sure. Otherwise, I installed everything again and went for another drive.

 

Shifted perfectly normal. Under light acceleration, it shifted into second gear at 2000 RPM. Medium acceleration, 3000 RPM. Hard acceleration (not full throttle), 4500 RPM. The 1-2 shift was not as rough, and the 2-3 shift was perfectly normal. Didn't hang or go into neutral. I drove it for about 10 minutes, got it up to temperature, but not too long since the water pump gasket is leaking a bit. It drove great!

 

After I got back from that drive, I turned the car off then turned it back on. Power light did not flash.

 

I guess I should be happy that it's back to normal, but I'm not confident it'll stay this way. It feel like a wiring issue, since it seems to be "on or off" (works or doesn't work; no in between). Much like it was with my IACV on my Loyale, that ended up being a connection issue. If that looks like the TCU, let me know and I'll follow the wires back from there. None of the wires seemed problematic visually, but I'll do more thorough testing if that is indeed the TCU.

Edited August 17, 2014 by jj421

[ossa55]

I have a 1994 Legacy that was acting exactly the same way. I t was not acting this way until we took it to a shop for a bad TPS problem. They replaced the TPS and then replaced the wiring harness plug to the TPS   and spliced it about 3 inches from the plug- in. Now it acts exactly like the guys problem above. Someone told me that when he spliced the wires it changed the resistance value and that I would have to replace the engine wiring  harness. Does this sound correct?

[jj421]

I'll let you know if I do anything to fix the problem. Right now the Impreza is sitting, half taken apart, waiting for a water pump to come in the mail.

 

I don't see how splicing wires would change the resistance, unless the splicing job was done poorly or a different gauge wire was used.

[jj421]

Well, new water pump is installed and car is running fine. However, it's still shifting weird unless I go through the gears manually. I'll have to track down the wiring when I get a chance. Kinda starting to annoy me.

[jj421]

So I want to update this thread. The car started running worse. Sometimes it would run rough at idle, and I'd only have barely any throttle or full throttle. Anywhere in the middle and it would just bog down and the whole car would shake/vibrate. I didn't pay attention to the RPMs, but it happened most often around 60 MPH.

 

I have installed a new TPS (got a used one off eBay). I installed it and noticed no difference. Car was still running rough. Also, when in neutral or park, if I rev it, it sputters until ~2000 RPM and then it revs fine. I threw a new fuel filter on there, but that didn't change anything either.

 

I also notice that if I have it in drive, it seemingly shifts from second gear to fourth gear. Then after about 5 seconds, it decides to go into third gear. I remember seeing a couple threads on the "skipping third gear" problem. I'll have to find those again.

 

Ugh, I'm getting a tad confused. Apparently the TCU is behind the radio/center console? I'll have to take a look. Have I ever mentioned that I hate automatic transmissions?

[jj421]

I believe I have found and fixed the issue. In the quest to fix the sputtering/misfiring, I found the spark plug wires for cylinder 2 and 4 were arcing really bad. At night, I could see it arc between both wires over a span of about four inches. Wrapped the wires in electrical tape, but they were still arcing through the tape.

 

Today I put in NGK plugs and wires, and that seems to have fixed everything. Car runs fine, no sputtering or misfiring. And it shifts perfectly now. I can actually keep it in drive without shifting manually.

 

I was talking with my friend and he said that in his experience, if the engine is not running right, the TCU won't know what to do and will send random codes. I'm still getting a flashing power light at start-up, but I presume it'll go away once the computers relearn everything. I'll post again in a few days with an update.

[jj421]

Well, after driving it a couple hundred miles, the transmission issue has presented itself again. So I think I will eventually do a fluid/filter change.

[idosubaru]

The JC box you took a picture of is the TCU

There's also the AT wiring on passengers side of engine bay that can also be disconnected.

 

After driving it - check fluid while idling - is it full of bubbles?

 

Probably dead ends but:

1.  check the transmission pan - is there any sign of damage or prior repair?

a.  if there's signs of damage - it could be dented and pushed up into the wiring/solenoids, there isn't much clearance at all between the pan and those components.

b.  if there's signs of replacement it may have been damaged, replaced, but the wiring/solenoids are still damaged.  unlikely without a code of course, but worth a ten second glance at the pan.

 

2.  sounds like you may have done this already - wiggle the wiring aggressively (in reason of course) while the engine is running.  start at the TPS and work your way back as far as the harness allows.  a compromised wire will show itself by affecting engine running while you massage the wire.  i located one like this years ago - no codes, couldn't find the issue - car ran terrible sometimes.  notable change in engine running when doing test listed above....splice in a used TPS wiring sensor and all was good.