'94 Convertible ** S13 auto trans prob = NOT auto trans problem

[honeybus]

[Since many (most?? all??) S13 convertibles are automatic transmission, I though I could get a better response by posting here, in addition to the Tech Board.]

I thought my problem was my S13 auto trans, but after replacing the AT, the same problem popped up.

Symptoms: S13 auto trans 'down shifts' on its own from OD to 3rd, and then to 2nd with a steady and light pressure on accelerator @ highway speeds, and speeds over 35 mph.

scenario:

240SX 's auto trans runs fine

1) I replace the alternator, I run the 240SX and then determine that FI #2 is dead.

2) mechanic agrees and mechanic replaces the #2 FI

3) 30 miles and two days after mechanic work, which is also about 50 miles after my alternator R&R, the auto trans goes into 'down shift' action. When down shifted, there is no power thru the auto trans and any more gas pedal only runs the revs way, way up.

If I sit quiet on gas pedal and trans will 'up shift' to OD. Then, in a few seconds same thing happens: 'down shift' for 3-5 seconds, and 'down shift' for 5-10 seconds and after 20 seconds it returns to Over Drive.

4) mechanic said not his doing ! ! ! I took the 240SX to an auto trans specialist. Honest shop. Said ATF was pink and odorless; we (shop and me) saw no shavings in AT pan after it was pulled/removed. AT shop had no idea what the exact problem was.

5) replaced 'bad' AT with known, good used AT. Outstanding results for the first few (25) miles!!

6) 30 miles after good ued AT was installed, and occurring the next day, the exact same symptoms. EXACT!!

I have the FSM at home, but nothing there I could find describes these symptoms.

The auto trans specialty shop said to rebuild the trans (obviously not the right diagnosis!!)

Would a NISSAN dealer be able to diagnose and PIN POINT the cause of the symptom. Accurately and correctly !! What equipment should they have to do this, other than a 'code reader'?? -Yes, I am showing a CHECK ENGINE LIGHT as I have for the past three years. Code was 32, EGR code. Couldn't find the problem, so light always on...

I know this is a technical question, sorry

Barry Burneskis [email protected]

[guyaverage]

[educated guess] Throttle position sensor is out of whack/defective/loose.[/educated guess]

You might want to swap out your tcu (transmission control unit) with a different one if that doesnt work (search ebay and junkyards, should be able to find one pretty cheap).

[JeromeS13]

It sounds similar, but not exact to a problem that I previously had. I swapped in an auto transmission from an S14 when mine went out. However, it wouldn't manually shift and would not stay in overdrive. The only way it would shift into overdrive was if I had the gas pedal SLIGHTLY pressed.

Run through the AT diagnostics mode in the FSM. If it will not allow you to enter the mode, chances are that its your inhibitor switch. The inhibitor switch is the sensor that is mounted inboard and adjacent to the actual gear selector on the transmisssion. Did you swap those out or did you use the one that came on the transmission? It sounds like that is bad or needs adjusting.

[honeybus]

Thanks guyaverage and JeromeS13:

Guyaverage, is the TCU the same thing called ATCU?? Is the TCU the little shinny box behind the ECU (electronic control unit) in the right floor foot panel?

JeromeS13, I think my mechanic used the wires and things from the 1st Auto Trans when he installed the 2nd AT. Since I have the 1st AT on my garage floor, should I be able to see the 'inhibitor switch'?

Update: last evening I checked my 'check engine' codes. I get 32 - EGR function (normal for me) and a new 34 - knock sensor.

Since the knock sensor is right around the Fuel Rail. My mechanic replaced FI #2, and perhaps messed up something. The first time I got this problem was 25 - 30 miles after his work. Then the 2nd time I got this problem was 25 - 30 miles after the 2nd AT was installed. My trip meter is still just over 100 miles, so from the start of the alternator replacement (me) to the #2 FI replacement (mechanic) to the replacement of the AT (mechanic) is just about 100 miles!!

TIA

[JeromeS13]

Those have no effect on the transimission. However, even if he did swap the inhibitor switch, it could be out of adjustment. Yes, you can see if its still attached to the old transmission. Just look for a weird looking thing behind the gear shifter with a harness coming off of it.

Have you tried running through the AT diagnostics mode yet?

[honeybus]

JeromeS13, I don't have the smarts to figure out the FSM. I have been r\trying to track down a code 32 (EGR) for three years without success. Now I also have a code 34.

The only symptom that I 'may' have is "Does A/T hold lock-upat the specified speed?" I don't know what LOCK-UP means.

And, "Does A/T hold lock-up condition for more than 30 seconds?" I gues it means that the lock-up (what ever that is) should be for more than 30 seconds...

Damn!! I see on page AT-21 the "Vehicle Speed when performing and releasing lock-up"

With OD on , and at full throttle, vehicle speed when lock-up is "ON" is 99-104 MPH. Who in the heck goes that fast on the roads.... OK,, at half throttle with OD on, lock-up is "ON" at 70-75 MPH

So I guess LOCK-UP is not what I am seeking.

These is something called 'Diagnosis by CONSULT' I guess that is something special.

No, I didn't run through the A/T diagnosis, but nothing I read in the A/T section of the FSM describes my symptoms.

Barry

[JeromeS13]

Follow the self-diagnosis (without consult) on page AT-29 and see what those results are.

[honeybus]

Sunday update and road test::

You know my symptoms: after running a short while, the 240SX will not hold 4th gear, but will drop to 3rd and 2nd quite instantly, and my revs will go up accordingly, up to 4-5k if I am not careful. There will be revs but no power, seemingly like the trans is in neutral.

Update: When fresh out of the driveway today the 240SX convertible drove like a dream for the first 10-13 miles. At mile 16, the symptoms started, but like a build up. And at 20 miles from fresh startup, the dropping and slipping was very, very bad.

After the first 25 mile run today, I wound up at a spray wand coin car wash. I cleaned the engine, washed it with spray soap, and rinsed the engine with fresh water,

When I pulled in to the spray wand coin car wash booth, the 240SX was acting up. 25 miles. When I pulled out, it was like a fresh virgin, and quite well behaved. I thought I spray wash fixed the problem. Apparently, all I did was cool the engine down.

I though I would satisfy myself that all was fixed by doing a 10 mile out and 10 mile back trip on the interstate.

I only got 7 miles when I decided nothing was fixed, and started the 10 mile run back home.

Miserable.. It got worse and worse, and I was doing max speeding at 30 mph on the back roads. It just would not hold a higher gear, even if I tried running with OD off.

Another amazing observation is that when I took my foot off the gas pedal, the RPM went down to idle speed, like 700 RPM. And the car seems to be in neutral, just coasting down and up a hill. I would have like to prove that observation by leaving it in Drive and seeing if the car would creep forward when it came to a rest, or if it would hold on an up grade.

That's all. Any other / more thoughts??

Barry

[honeybus]

Follow the self-diagnosis (without consult) on page AT-29 and see what those results are.

Sorry, JeromeS13, I am a slow typist...

I will go out and do AT-29.

barry

[honeybus]

OK, I did the AT-29 and I read the OD flicker like this.

First LONG ON, then 10 more flickers, number 3 flicker longer than other nine.

I guess the first real long light is just to tell you the starting point.

3rd judgment flicker means “Throttle position sensor circuit is short circuited or disconnected”

Perhaps I disconnected that TPS when I installed the alternator. I was coming in over the top and going in from the bottom, never having done this before.

I disconnected a bunch of hoses above the area, and that long plastic air damn that runs just behind the radiator. What does this TPS connection look like??

Or could it be something that my mechanic disconnected (he had a helper, and sometimes those helpers are THICK!) when he installed my new #2 fuel injector. He said he had to do the install twice because something about a lot of fuel spilling around from the new FI.

Barry

[honeybus]

Is the TSP somewhere in this pic that I could find easily??

This is the area where I took off all those hoses, including the radiator hose.

Oh, I forgot. I had my mechanic replace the radiatior hose, too, when he was doing the #2 fuel injector..

Oh, I forgot this too::: I had the rubber hose off the throttle body and I sprayed a whole bunch of carb cleaner (or starting fluid) up the throttle to clean out the intake. Something to try to get rid of the EGR code 32... Alternator replacement time... before FI replacement time....

barry

[JeromeS13]

Yeah. Its on the driver's side of the throttle body.

[honeybus]

Yeah. Its on the driver's side of the throttle body.

So I guess I'll have to take the top radiator hose (the new onw!!) off to get to it..

barry

[honeybus]

So here's what the car looks like. (It's the white one in the front)

[JeromeS13]

So I guess I'll have to take the top radiator hose (the new onw!!) off to get to it..

barry

No, you don't.

[guyaverage]

See the sticker on the radiator hose, the plug just to the right of it in the picture goes to the TPS. There is one other plug that connects directly to the TPS, make sure its plugged in too.

If you have to take off the TPS to replace it, you will have to unbolt the throttle body from the intake manifold first otherwise and slide it off the studs, otherwise the TPS wont have enough room to slide off the throttle body shaft.

When I get to work tomorrow I can send you directions on how to check it out. I dont have time right now.

[honeybus]

Thanks, Guyaverage and JeromeS13

I found this picture on the internet. It may be a picture of the throttle with the TPS.

There are two decent S13 autos out in the yards, and I will want to know what and how to pull off the right stuff.

Also, I am pushing a cde 34, which is a knock sensor failure (too high or too low) code. I will want to pull one of those off also, 'cause I can probably get it for $5.... Throttle + TPS = about $10

[JeromeS13]

You need to make sure yours is dead first.

Follow this: http://www.240sx.org/faq/artic...m.htm

Then go from there.

[honeybus]

Thanks, I am printing the FAQ and going back home to read up somemore.

Here is anther picture of a throttle body I found, still trying to determine what the TPS looks like.

""Here is a picture of the 240SX throttle body. Note that this unit has the potontimeter type setup.""

I think it is the black screwed in item with the pig tail.

[JeromeS13]

Yes, thats it.

[bige240]

Did you try checking for transmission fluid leaks or even the fluid level? My car did the same thing and I was about a half quart low. Filled it up and it was fine. Check the level when the engine is Hot and cold... You may also have a leak in your egr (exhaust gas release) system.

[guyaverage]

The EGR wont affect the transmission shifting. It will make the engine run like crap if it is stuck open, but thats it. If its stuck closed, you'll never know the difference.

As far as the TPS, if you look at the first picture posted (not sure what that second one is from), you see the plug attached to the wires, but you also see 3 electrical contacts on the TPS itself. On your TPS, you need to disconnect the plug to get access to those contacts so that you can adjust the TPS properly.

You will need a multimeter to check for continuity (any el-cheapo $8 multimeter will do). You are going to need a helper. I'm going to write this like you have no idea what you are doing. It will actually sound more complicated than it is. Its actually really easy and shouldnt take more than a half hour or so.

WITH THE ENGINE OFF AND YOUR FOOT OFF THE GAS PEDAL, there should NOT be continuity on the bottom two contacts. If you have continuity between the bottom 2 contacts, with your foot off the gas pedal, the TPS is screwed, replace it.

WITH THE ENGINE OFF AND THE GAS PEDAL ALL THE WAY TO THE FLOOR, there should NOT be continuity on the top 2 contacts, there SHOULD be continuity between the bottom two (by now you have seen that obviously with 3 electrodes the middle one is always part of the checking). If the TPS fails this check, its screwed, replace it. If its ok so far, keep going.

Now, start the engine and just barely touch the gas pedal until the rpms sit between 900-1100 (the manual I think says 900 plus or minus 150, just shoot for 1100, it makes things easier, thats where I set mine and it works fine). There should NOT be continuity on the top 2 contacts OR the bottom 2 at 1100 rpm. (Note: Stay clear of the fan while you are doing this!) If you have continuity between the BOTTOM 2 contacts at 1100 rpm, the TPS is bad, replace it. If there is continuity on the top 2 contacts, its probably just out of adjustment (stop the engine). Loosen the screws that hold the TPS to the throttle body (you will need to small hands and/or small tools to do that) and rotate the tops of the TPS just a SMALL bit up, or towards the back. Tighten the screws (just snug enough to keep the TPS from rotating, they dont have to be really tight for now) and now see if there is continuity on the top 2 contacts at 1100rpm, if so its still out of adjustment. Loosen the screws, rotate it towards the back a tiny bit, tighten the screws, start the engine, put it to 1100 rpm, and check the top 2 contacts again. Keep doing this until the top 2 contacts have continuity at idle (foot off the gas), but no continuity at 1100 rpm. If you cant get it to do this, get a new one. If you can get it this far, tighten the screws. WITH THE ENGINE OFF AND THE GAS PEDAL ALL THE WAY TO THE FLOOR, there should NOT be continuity on the top 2 contacts, there SHOULD be continuity between the bottom two. If this is what you get, you're getting there. Tighten the screws and reconnect the plug.

NOW, the other plug, the one that connects to the wires coming out of the TPS. Unplug it. You will see 3 contacts in there also. Check the resistance reading between the center contact and either of the outside ones. You should get a reading of about 1000-3000 ohms from the center contact to one of the side contacts, and about 9000-11,000 ohms between the center contact and the OTHER side contact. If it checks ok, now check it again, but with the gas pedal to the floor. The resistance readings will be the opposite of what they were. The center to side contact that had 1000-3000 before should now be 9000-11,000 and the one that had 9000-11,000 ohms should now be 1000-3000. If this isnt what you get, or if the readings are way out of this range, replace the TPS. If it checks ok, you're almost done.

Plug everything back in and start the engine, if it idles where it did originally, you're done. If it is idling about 100-300 rpm higher, rotate the TPS, in tiny increments, towards the top/back until the idle returns to normal, then tighten it up. You're done.

Now, there are I think 3 plugs, between the battery and the coolant tank. Make sure they are all plugged in. If not, do the obvious. If they are plugged in, unplug each one of them and check the contacts to make sure they arent gunked up or corroded. If so, clean them up, if they look ok, plug them back in.

Take if for a spin. If it shifts ok now, send me a beer. If not, I would replace the transmission control unit (ATCU). Yes, its under the passenger side kick panel by the engine ECU. You should be able to get one in a junkyard or off ebay pretty cheap. If after all of this it still doesnt shift right, pull your hair out. I would.

If you dont want to do any of this, drive to Cincinnati and I'll do it for you, I've done it a million times. Let us know what happens.

[honeybus]

Now, start the engine and just barely touch the gas pedal until the rpms sit between 900-1100 (the manual I think says 900 plus or minus 150, just shoot for 1100, it makes things easier, that's where I set mine and it works fine).

There should NOT be continuity on the top 2 contacts OR the bottom 2 at 1100 rpm. (Note: Stay clear of the fan while you are doing this!)

Barry asks?? I guess I will have the plug OUT, right?? Or should I make a set of cheater wires and tap into them for the continuity checks..

Take if for a spin. If it shifts ok now, send me a beer.

Barry says!! Right now, it shifts beautifully for the first 13 miles. It starts to lose it at mile 16, and is completely wasted at mile 20. Because I was usually driving it just less than 13 miles any time I took it out, I did not see the problem, if it actually existed before the Alternator and the FI replacement . I will have to do the tests on a cold engine, and then take it out for a 20 mile round trip and measure / test on a warmed up running engine.

If not, I would replace the transmission control unit (ATCU). Yes, its under the passenger side kick panel by the engine ECU. You should be able to get one in a junkyard or off ebay pretty cheap. If after all of this it still doesnt shift right, pull your hair out. I would.

Barry says!! Yes, I am going to a junk yard this Saturday for the ATCU and the TSP/throttle and a few other things on the 240SX, plus some Porsche 914 stainless steel heat exchangers for a friend, and a few exhaust things for a VW bus (my other cars are VW campers, 1976 & 1978)

If you dont want to do any of this, drive to Cincinnati and I'll do it for you, I've done it a million times. Let us know what happens.

Barry cries¿¿ The 240SX won't go further than 20 miles without really wiping out the shifting / transmission. I doubt I could get it to go 50 miles if there was a nuclear attack and this was my only transportation to safety.

As you can imagine, I am 'dark' regarding the 240SX. When I was researching the code 32 EGR problem, I tore apart two 240SX's in the junk yard just to see how to get at things. I spent hours trying to find the pieces that were named in the various helper post on code 32.

The alternator was just a bit frustration at first because I did not know the right way to get at it. From the bottom or from the top. We have a library system that gives access to a repair procedures for many cars, and it is clear and has pictures. The FI was easy to diagnose, but not easy to figure out how to replace.

I guess I am spoiled by my VW campers. I can do most anything with them, or learn fairly easily anything new.

Thanks. I will do the tests, probaly AFTER I pick up the parts from the junk yard... ($10 for a TSP, and I guess the throttle comes with it...)

[bige240]

Thank you... I know the egr doesn't have anything to do with the transmission shifting...He said he had 2 codes one for EGR and one for The TPS. If he is getting an egr code, that is usually a vac leak somewhere....That's why I removed all the emissions off of both of my 240's. all those vacum lines and associated crap are space taking and do nothing. You are getting him Deeep into a project that he is not very knowledgable about. The tps's are pretty quirky, and he probably does need a new one. The inhibitor switch is a good place to look also...This guy obviously has multiple problems with his car and you are covering only one of them.

[guyaverage]

On a 1994 the ECU will not throw a code for a vacuum leak or a mechanical failure of the EGR system, it will only detect open circuits or short circuits in the electrical control part of the system (solenoids, wiring, etc). The EGR valve and piping could be on fire (or not even there), but as long as the electrical part is intact and functional, the ECU doesnt know or care. Since the EGR doesnt have anything to do with this problem, and if the engine runs fine even with the EGR code, then that is the least of his problems.

He already has a code for the TPS, its not going to get any more screwed up than it is. Something in the electrical circuit is either shorted, or open, the ECU has already figured that out. What I showed him to do is going to help identify whether the TPS itself is bad or if associated wiring could be the issue. And if the TPS is bad, what I showed him will get him able to adjust the replacement one good enough to get him back on the road. Knowledgable or not, he sounds capable and willing to learn, let him have at it.

Barry- Yes, plug out while doing the continuity checks. The 5-spd TPS is adjusted while plugged in (checking voltages) but the automatic TPS is adjusted using the closed throttle/wide open throttle switches which is what those 3 contact are, so the plug has to be off. Same thing for checking the resistance on the wired plug.

Also, you said they have a couple of 240's in your junkyard? If you happen to come across a spare ATCU (other than the one you are going to get), if you can get it dirt cheap ($5-$10), I'd love to have a spare. I'd like to do some experimentation on one and I dont want to screw up the one I have, and I cant find one locally anywhere.

[honeybus]

Also, you said they have a couple of 240's in your junkyard? If you happen to come across a spare ATCU (other than the one you are going to get), if you can get it dirt cheap ($5-$10), I'd love to have a spare. I'd like to do some experimentation on one and I dont want to screw up the one I have, and I cant find one locally anywhere.

Guyaverage, there are three junk yards that I go to on my regular rounds. There is only one ATCU in one of the three yards. These yards are reasonably priced. Crazy Ray's in Baltimore

There is one junk yard in Woodbridge VA that I went to on Sunday past. There is a '91 auto there that looks like fresh pickings. This yard is completely unreasonably high in ANYTHING. Only if I cannot get something at the other three. Penny's in Woodbridge VA [[I forgot. The '91 is a hatchback with 125k on the odometer...]

If I come across another fresh A/T 240SX at the other three yards, I will will be sure to pull the ARCU. These pick and pul yards do not have a price list for an ATCU, so I guess they are 'very reasonable'!!

Barry


Modified by honeybus at 12:38 PM 9/21/2006

[94_240sx]

I don't want to create a new thread, so will just post here. This is my story. Back in 1999, I heard whining noise one day and a couple of minutes later, car wouldn't move. Turned off the ignition, waited bit and it worked, but problem didn't go away. It happened again and again. I had enough, so paid some shop to rebuild it. Since then, it's been running great, but I noticed this problem recently. It only happens when O/D is off.

I drive around 40-50mph with O/D off. At this point I'm going with 3rd gear. Right? Let go of the gas pedal and gear changes 2nd and 3rd back and forth, so RPM goes up and down and up and down.

This never happens when O/D is on. Since I never turn off O/D, it's not bothering me much, but any ideas?????

[honeybus]

He already has a code for the TPS, its not going to get any more screwed up than it is. Something in the electrical circuit is either shorted, or open, the ECU has already figured that out.

What I showed him to do is going to help identify whether the TPS itself is bad or if associated wiring could be the issue. And if the TPS is bad, what I showed him will get him able to adjust the replacement one good enough to get him back on the road. Knowledgable or not, he sounds capable and willing to learn, let him have at it.

Also, you said they have a couple of 240's in your junkyard? If you happen to come across a spare ATCU (other than the one you are going to get), if you can get it dirt cheap ($5-$10), I'd love to have a spare. I'd like to do some experimentation on one and I dont want to screw up the one I have, and I cant find one locally anywhere.

GuyAverage, than you for sticking with me. On your first note "Something in the electrical circuit is either shorted, or open" I have this additional observation I posted elsewhere.

Barry said: " The power door locks on my '94 AUTOMATICALLY and spontaneously LOCKED, by themselves on two recent occasions [Mid and Late Sep 2006, like now time.]: I opened the drive door from the inside to get out, and a few days later this happened when I opened the driver's door from the OUTSIDE to get in. . . .Two times in one week, and just now, after 4 years of service." I think I have other electrical problems....

GuyAverage, the 240SX is not my primary wheels, but I would like it to be I need to work on my 1978 VW bus daily driver for about two weeks before winter sets in.

GuyAverage, I picked up all I need from the 122k 1992 240SX auto hatchback at Penny's in Woodbridge VA (BTW, local Wash DC people, it WAS a clean car before yours truly got to it). I am attaching a picture of my stash that I got 2 days ago, Monday 25 Sep 2006. It includes a TPS, knock sensor, ECU and ATCU. Also a radiator overflow and intake manifold. GuyAverage, if you can use either of the last two items, please PM me your Ohio mailing address and I will send them out to you for karma. I owe the community a lot!!!

I did not change out any parts, nor did I test the 240SX TPS because I am now clean on my judgment code (#3) but still having the transmission problem. The engine light is off when I start the car for a few miles, but comes slightly on after about 5-10 miles. I may be throwing just one code...

I plan to check the TPS readings when stone cold, since the (replacement) transmission runs fine when cold. Then run the 240SX until I get very drastic down shifting and limp home and check the TPS when the problem is there.

Not yet, though. One more run to the junk yard Saturday for the other 240SX ATCU (the ECU is probably $$30, too expensive for ****s and giggles) and grab a pair of Porsche 914 stainless steel heat exchangers to sell on eBay. Those damn things are EXPENSIVE!! And a few other items.

Just an update. Later.

[guyaverage]

You are lucky to have a good supply of 240's in your local yards, I scoured some local yards around here and the only one I could find was a 1990 that looked like it had been hit by an Iraqi roadside bomb. A few months ago I would have paid you decent $$ for that overflow tank because mine was a mess, but I went diving into the local yard and found one off a Toyota Tercel that looked like it would work, so after $5 and with special thanks to Home Depot I made some brackets for it and bolted it to some factory bolt locations on the shock tower and I have been happy with it ever since. My intake boot is in great shape, but thanks for the offer. Now if you can find an extra 1991-1994 ATCU.........

Your plan to test the tps hot and cold is a good plan. You might also want to check the temperature sensor hot and cold readings too (2500 ohms cold, 300 ohms hot). The plug for it is behind the battery, check out page AT39 in the factory manual. Other things that you should really also check are the speed signal circuit and revolution sensor circuit (pages AT-32 and AT-33).

Since you have the same symptoms on 2 different transmissions I still think either the ATCU is faulty or there is a problem with the wiring between the sensors on the transmission and the plug on the ATCU.

[honeybus]

GuyAverage, just to let you kow I haven't given up just yet!!

Sunday night and a few days before Sunday the 240SX was not showing any codes. Sunday night I ran through the AF-29 test when the engine was stone cold, and I got the #3 judgement code. Then I let it idle in the driveway until it came up to operating temperature, and there WAS NO #3, or any judgement code...

This is counter intuitive to the trans down shifting problem, which happens at normal operating temperatiur (about 16 miles)

I guess I am going to have to take the 240SX back on the road and see if the Check Engine codes come back (32 and 34), and the A/T judgement code #3 comes back...

(Last Saturday there was a second late 240SX A/T coupe in the yards, but I could not find the ATCU!! I wound up pulling an extra ATCU from a '88 because I was bored... )

Barry