capezig

We are tinkering with a 1994 EX with a flaky transmission. First notice was missing the downshifts when slowing, such as around a corner and then getting back in the gas without stopping. The transmission acts like it has gone to neutral. The cure is to come completely off the gas, let the engine idle all the way down, and then it will catch a gear. If you come to a complete stop, it shifts through 1st and 2nd pretty normally. Now, unfortunately, the transmission seems to get stuck between gears, especially 3rd and 4th, and hitting hitting the gas just winds out the engine without going anywhere. The 'cure' again is to allow the engine to idle all the way down until it engages in the next gear, and then ease back into the gas. The fluid has had 2 drain and refills with genuine Honda fluid, the shift and lock up solenoids have been changed with ones that click vs. our old set the did not click when putting 12v directly to them. I opened up the TCU and there was no evidence of burned or leaking capacitors. There are no codes displayed when shorting out the blue connector below the dash on the passenger side. Reading through the forums I think next is to check the throttle/trans cable, but after that I am stumped...any help appreciated, we need to get this car going right for my daughter to drive...

MAD_MIKE

Check for stored codes.
Verify NM/NC sensors are clean of any ferrous material.(remove, clean, reinstall)
Back probe TPS and verify linear voltage change.

capezig

Mad Mike, thanks for the response. I have checked for codes before and found none, but I will check again tomorrow. I get the back probe of the TPS and will do that with the instructions from our Haynes book... But, I don't recognize the "NM/NC sensor" reference?

MAD_MIKE

If no codes are stored, verify that the 7.5A memory fuse under hood is not blown.

NM/NC sensors are hall effect magnetic pickup sensors that are located in the right side cover of the transmission. Turn your steering wheel to the right and then look behind the wheel. You will see the right side cover of the transmission. There will be two sensors located at about 10 O'clock and 2 O'clock, use a 10mm box wrench to remove the locking bolts, twist the sensors to break free and carefully prise the sensors up and out.

capezig

Mad Mike, I found the info on the NM/NC sensors...I will check these too and post all results.

MAD_MIKE

FWIW, throttle cable to trans should not have any slack, but should not be pre-tensioned either.

NM/NC sensors should have a resistance of 400-600Ω

capezig

Mike, On the TPS: reference voltage was at 4.98, throttle closed starts at 0.47v and maxes out at 4.33v at full throttle deflection. On the NM/NC sensors, the aft tested at 490 ohms, and the forward at 488 ohms. Anything on the sensors magnetic tip seemed to be of the minimal slime variety...but I don't know how much of this it would take to mess up the readings. I must not have been quite awake when I started this morning because I checked the fuses before checking for codes...oops...but as I said before, we have not had any in the past and no blinking D4 light ever. The throttle to trans cable does not seem tight at rest, and does start to move the lever immediately with the throttle moving. Test Drive: the car does seem to go up through the gears correctly and pretty smoothly. The only issue still seems to be getting lost downshifting sometimes. If you are going 40, and brake to come down to 20 fairly quickly, and then get back in the gas it's like the car is in neutral and just revs up and goes nowhere. If then you come completely off the gas and let it drop below 1000 rpm's it will then 're-engage' and go back up through the gears as it should...???

MAD_MIKE

If the trans is going neutral after gear shifting have you verified the fluid is full?
On older/worn transmissions the circuits may not stay fully charged and can leak down pretty quickly. Warm the engine transmission up. With the engine running verify the ATF is within the hash marks, if not fill so it is.
Then place the gear selector in every gear for a few moments while stopped to charge each circuit. Immediately place the car in park pull dipstick wipe clearn, reinsert fully, pull out and check level. It should be at minimum at the lowest level.

If you live in a hilly area, or your commute is through hills with curves/offcamber turns, I would suggest doing the above and filling the trans til it was near the upper mark of the hash on the dipstick.

The VSS controls downshifting as well as speedometer output. However, if it is failing, it can cause the TCU/Transmission to go into a limp mode and prevent shifting as well. It can become dirty and need to be cleaned as well.
VSS - Vehicle Speed Sensor Troubleshoot, Repair, Replace - How To.

capezig

Mad Mike, the fluid is ok...we have done a couple drain and refills with Honda fluid...but the VSS does not seem to be...it failed the bench test with no 5 volt pulses on the output (double checked terminal assignments)when spinning it by hand or with a cordless drill, and the fit of the little drive shaft in the VSS is very sloppy. I have a new one on the way...fingers crossed...

capezig

The transmission saga continues...the new VSS was installed and the fluid was topped off to the top of the hash marks on the dipstick...but it still does not shift right. From a stop the trans does shift to second at about 21 and then third just over 30. The 1st to 2nd shift feels good, but the 2nd to 3rd seems a little sloppy sometimes, sometimes fine. The downshifting is still a real problem...If running at 35 and slow to 20 the transmission can't seem to catch a gear, or not the right one. If you stay off the gas completely and let the rpm's drop below 1000 rpm it will always downshift correctly to the right gear.

It is about 20 minutes to the highway from the house so I have yet to test it again over about 40 mph...

We have:
done a couple drain/refills with genuine Honda fluid,
changed the shift and lock up solenoids with used but good ones that click w/ 12v applied,
changed the VSS with a new one,
checked the throttle body to trans cable tension,
opened and inspected the TCU and found nothing burned or leaking,
pulled out a little gray hair from my head...

capezig

Mad Mike...after changing the speed sensor with new I also did another drain/refill of the trans fluid. There was some grey slime on the magnet. I drove it for an hour and then immediately did another drain and refill. During the hour of driving the shifting got worse and worse, getting to the point where the only way to shift up or down was to come off the gas for several seconds until the engine dropped to an idle. But...I just checked for codes and now we have a '15' and the D4 does not flash while the engine is running. I found this re: that code that says it was for a 1994:
"Code 15: D4 light OFF:
Disconnected main shaft speed sensor connector
Short or open in main shaft speed sensor wire
Faulty main shaft speed sensor"
Is this the right info and is this referencing the sensor I just changed, or something else? Did I need to do some kind of reset after changing that sensor to let the TCU know it was there and new like pulling a battery lead?

Edit: wake me up...I'll bet I should pull that 7.5 amp fuse under the hood to clear the memory, drive it again and see if it comes back...

holmesnmanny

Take a real close look at the connector that the vss plugs into and see if its corroded.

Also they do get old and the inner metal/plastic pins can break or deform over time.

Just have to look closely.

Also make sure the connector was closed all the way. Some vss's are a real pain to connect/close fully.

MAD_MIKE

This is correct.
Not all TCU codes will illuminate the D4 lamp(goofy I know), you have to check and verify that there is a stored code.
AFAIK you do not have to clear the 15 code for the trans to work properly after fixing the code 15 issue. But it is a good idea to clear so that you know that the code is not being reset.

Disconnect 2pin connector from NM sensor, and recheck resistance of NM sensor.

Is the resistance correct?

No.
Recheck pins and sensor for damage to sensor wires, if no damage found, replace sensor.

Yes.
Remove the 22pin TCU connector. Check for continuity of pin D12 to ground, and D19 to ground.

Is there continuity to ground?

Yes.
Check for damage to Orange/Blue or White/Blue wires of NM sensor harness.

No.
Reconnect 2pin NM sensor to harness and recheck resistance at 22pin connector D12 and D19.

Is the resistance between 400-600Ω between D12 and D19?

Yes.
Check for loose, corroded, damaged pins/connector in the harness and at the TCU itself. Perform similar test on for code 9/NC sensor/harness(D15 & D17(Blue/Green & Blue Yellow wire check))
May want to confirm not a faulty TCU with a known good spare TCU.

No.
Check for continuity of D19 through harness to sensor.

Is there continuity?

No.
Repair open in Orange/Blue wire to sensor.

Yes.
Check for continuity of D12 through harness to sensor.

Is there continuity?

No.
Repair open in White/Blue wire to sensor.

Yes.
Check for loose pins/connector at TCU.
Test with a known good TCU if no loose/corroded/damaged pins found.

Tip, while doing these tests, wiggle the harness from time to time. If there is an intermittent ground or break it may not show up without giving the harness a shake during testing. Similar to the vibrations/bumps that occur while the car is being driven.

If slurry has appeared on the drain plug after a previous drain/refill, some of that slurry may have been slung onto the magnetic pickup of the sensor. Recheck that it is not fouled with ferrous material.

And finally.
A code 15 may not be an electrical problem.
There could be a mechanical problem inside the transmission. Although IMO you would notice such a problem, not just an erratic/incorrect shift event.

As Ser Manny has stated, recheck all your connectors again. Verify the connectors push together and the pins are not damged/missing.

Verify the battery is fully charged/holding a charge, battery terminals are clean and tight, and that engine/trans/harness grounds are clean and tight.

capezig

Thank you for sticking with me on this...it is driving me nuts at this point...

I cleared the memory and went for a drive, taking notes, this morning.

From a stop, with easy throttle pressure and in D4, the car kind of slides into 2nd at about 20mph (not a crisp shift). At about 30mph the rpm's start to wind out with no vehicle speed increase. Pull off the gas completely, allow the rpm's to drop and settle below 1000, and it locks into gear (but I am thinking maybe its 4th not 3rd?) Continuing easy throttle pressure I could get up to 70 mph at about 2500 rpm with no apparent further shifting.

On another similar run up, and after getting through the missed 3rd gear like above, I punched the throttle at about 50 mph, and the rpm's wound out and the transmission dropped out of gear. I flicked it into D3 manually and it went into gear with an associated increase in rpm like you would expect from a downshift at that speed.

On the way home, at a steady 35 mph, with constant throttle pressure, I was able to manually shift from 4th to 3rd to 2nd and back again at will.

Total drive time about an hour. I checked for codes again and there were none.

?? Applying basic shade tree logic, it would seem to me that we might still have guts in the transmission if I can manually shift between gears?? And that it is a control issue, as you guys seem to still be pointing toward with the above provided T/S sequence. I will get to that asap and post back.

Thank you!

capezig

Gentlemen; I ran through the t/s for the nm and nc sensors and it all checks out good. Only twist was that the color coding described was reversed between the two sensors if I am seeing the previous diagram correctly.

But, then I went back and re-checked the shift solenoids with 12v direct. the lower of the two, with the blue w/ yellow wire does not sound as strong as the other...click is kind of muted. I thought this was a 'used but good' one, but maybe not so good.

Would this bad solenoid cause such an issue as I described after my note taking test ride with not being able to get into 3rd?

MAD_MIKE

The lower pair of solenoids are the 'Shift Solenoids', if they are not functioning/sealing correctly the shift will be soft/sluggish/vague/non-existent.

Pull the solenoid again and verify there is no crud on the filter and recheck how well it clicks. Jumper a ground to the main plate and then click test to each terminal. If you can identify which solenoid that does not 'click' you will be better able to determine if it is indeed the solenoid related to your shift event.

If it does sound weak, try flowing some solvent through the valve while clicking it on and off. If crud blows out and the clicking noise increaes in sound you may have just had built up junk inside the pintle valve seat.

Solenoids are spring loaded closed and magnetically held open. If the spring in the plunger valve has jammed or failed it will not close properly/fully. Electrically it will be fine(coil fine) but pressure and function will be incorrect.

Honda Electronic Transmission Problem- Troubleshoot, Inspection, Repair, Replace.

FWIW, Q-tip shaft is the exact same diameter as the pintle valve seat port. If when pushing on the valve you do not feel the spring loaded resistance of the valve, it may be the spring has failed. I would not recommend using anything hard as that may damage the valve tip/seat.

capezig

Mike, of the two shift solenoids, the one lower on the engine with the blue/yellow wire was the one not sounding right. I blew out and put the other set of solenoids back on the car last night, they clicked better both on the bench and on the car than the set that was in place. Hope to test drive tonight.

BSprick

I just picked up a 94 accord ex and am having similar problems. When going from 2nd to 3rd it goes into gear but I have to hold it into 3rd otherwise it pops out and goes to neutral. And I can't downshift from 4th to 3rd, it just won't go in. I was told the synchros could be bad, so just a thought.

holmesnmanny

Make your own thread. Dont threadjack.

BSprick

I was just giving a suggestion of what I was told it could be. I'm also going to look into the suggestions Mad Mike gave.

capezig

BSprick, it sounds like you might be working on a manual trans and this whole thread is about an automatic....

MAD_MIKE

Mea culpa, I should have been clear. Lower pair of solenoids are the shift solenoids. Upper pair are converter lockup solenoids.

Shift solenoids and Lock up solenoids function as A and B units.
Looking at the end of the disconnected solenoid pigtail with the locking tab portion UP wires are A and B.
Shift Solenoids
_A_ _B_
OFF_ON= First
ON__ON= Second
ON__OFF= Third(same as Reverse)
OFF_OFF= Fourth

capezig

Mike, I was on the right pair of solenoids, just didn't know how to tell A vs. B and the combinations , thank you. It was the A shift solenoid in the other set that was sounding pretty wimpy with 12v applied, which, in my simple mind, would seem to make sense with it going sloppy into second and then skipping to 4th...

And? In the solenoid off/on sequence, I am assuming that 'ON' is when the solenoid is getting 12v to pull the valve open?

Test drive this morning with the better sounding solenoid set makes me think we are onto something. Cold out of the garage she shifts well at 20, 30, and 40 (all ish) mph with fairly easy throttle pressure. No missed downshifts, seemed pretty good. Then as time went on, the shift at 30mph seemed a little slippy, and would take just a slight ease in pressure on the gas to get it to lock in right.

Shade Tree Theory?: could it be a difference in flow pattern through old, worn solenoid valve ports as the fluid gets warmer and thinner? The solenoids/springs are just tired and weak and don't hold as well warm?

MadMike, would this make sense at all?

capezig

Well, now it is worse than ever. Still, right from cold the transmission seems to act almost right for at least the first 15 minutes, then it starts to go downhill and by 30 minutes into the drive it will barely go. From a stop it is only through very gentle nudging that you can get the car to start moving at all without just winding out and going nowhere. Once moving, it seems to be stuck in 2nd, about 3000 rpm and going 40 mph. That is how we got the car home, and there it sits. I must say I am about ready to throw in the towel on this one...very frustrated...now parked next to the garage and covered in snow...looking pitiful...

capezig

still struggling with this thing...of note, every time I have done the usual 2 quart drain and refill, the magnet on the drain plug is covered with a thick coat of the grey slime with not more than an hour running time...how much of this stuff could there be? The transmission is slipping more than ever and not shifting anything that resembles normal. Is it time to just give up and look for a used transmission to throw in this thing or to send it to the big junk yard in the sky?