I'm hoping this is something simple. 1993 Accord auto trans doesn't lock torque converter in 4th gear. Revs are 2500rpm @ 90kmh (56mph). Just confirmed it isn't locking this AM, so haven't checked anything. Will start with fluid level ... anything else to check on these cars?
1993 Accord - torque converter not locking
- Thread starter NJC
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the brake light switch might be funky causing a non lock up. just one of many causes. mike
I used to drive a 1990 Accord EX Coupe with an automatic, had the same engine and transmission as the 1993 models. There are two common failures for those cars.
1) The transmission computer (TCU) tends to blow out a capacitor on the circuit board and malfunction, this happens with age. You can buy a rebuilt TCU for $175, it is easy to replace and is under the passenger floorboard carpet. It only has 4 10mm bolts, very easy to remove. If the ECU is malfunctioning you will get a blinking S and/or D light on the dash. I had to replace my TCU at about 110k miles. When my TCU died, the transmission wouldn't lockup the torque converter and sometimes would only shift between 2nd and 4th. The S light on my dash would blink after about 3 minutes of driving the car, indicating that there was a problem.
2) The vehicle speed sensor also has a tendency to fail on these cars. Again it is cheap and easy to replace if it does go bad. When the VSS went out on my 1990 accord the speedometer would randomly not work and the torque converter would unlock at random intervals while I was driving. Sometimes the car would also throw a check engine light, but not always. Replacing the VSS cured the problem immediately.
1) The transmission computer (TCU) tends to blow out a capacitor on the circuit board and malfunction, this happens with age. You can buy a rebuilt TCU for $175, it is easy to replace and is under the passenger floorboard carpet. It only has 4 10mm bolts, very easy to remove. If the ECU is malfunctioning you will get a blinking S and/or D light on the dash. I had to replace my TCU at about 110k miles. When my TCU died, the transmission wouldn't lockup the torque converter and sometimes would only shift between 2nd and 4th. The S light on my dash would blink after about 3 minutes of driving the car, indicating that there was a problem.
2) The vehicle speed sensor also has a tendency to fail on these cars. Again it is cheap and easy to replace if it does go bad. When the VSS went out on my 1990 accord the speedometer would randomly not work and the torque converter would unlock at random intervals while I was driving. Sometimes the car would also throw a check engine light, but not always. Replacing the VSS cured the problem immediately.
Temperature sensor on my Neon wouldn't allow the ecu to lock the converter. My ignition system wasn't to good at the time so the rich mixture caused a misfire code, otherwise I don't think a code would've been thrown.
I haven't noticed any warning lights/codes, and all gears seem to shift properly. The torque converter just doesn't lock ... both of the other Accords I've owned ('84, '88) would lock at 55mph.
Does it ever lock up? Or can you go even faster and still not have the converter lock up?
I did forget to mention one thing, on my 1990 Accord the converter would stay unlocked if the car was cold. I could get on the highway and drive almost 2 miles before the converter would lock. I think the TCU waits for the car to get up to temperature before it locks up the converter. Is it possible your car isn't up to temperature?
The only other thing I can think of would be the shift solenoids. They tend to get clogged with silt from the clutch packs as the transmission starts to age. This site has some awesome illustrations and descriptions on how to resolve this. I never had to remove the solenoids on my car but I bookmarked this site just because of the great info. It also explains the shift sequence for modern accords with the TCU (such as your car).
http://techautorepairs.com/transmission.html
(EDIT) I just read that link, they list the NC Speed sensor as a reason the torque converter doesn't lock up. Might be worth looking at.
I did forget to mention one thing, on my 1990 Accord the converter would stay unlocked if the car was cold. I could get on the highway and drive almost 2 miles before the converter would lock. I think the TCU waits for the car to get up to temperature before it locks up the converter. Is it possible your car isn't up to temperature?
The only other thing I can think of would be the shift solenoids. They tend to get clogged with silt from the clutch packs as the transmission starts to age. This site has some awesome illustrations and descriptions on how to resolve this. I never had to remove the solenoids on my car but I bookmarked this site just because of the great info. It also explains the shift sequence for modern accords with the TCU (such as your car).
http://techautorepairs.com/transmission.html
(EDIT) I just read that link, they list the NC Speed sensor as a reason the torque converter doesn't lock up. Might be worth looking at.
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90crvtec;
Before I go any further, I'll try and go faster to see if it will lock. I've only had it on the highway twice ... and according to that link (good source of info):
Quote:
When the speed reaches 60 - 65-mph or more the lock up torque converter engages. This is felt as a slight nudge. Shift sequence ends.
That's a higher speed than both of my other Accords.
Before I go any further, I'll try and go faster to see if it will lock. I've only had it on the highway twice ... and according to that link (good source of info):
Quote:
When the speed reaches 60 - 65-mph or more the lock up torque converter engages. This is felt as a slight nudge. Shift sequence ends.
That's a higher speed than both of my other Accords.
For what it's worth (not much
) my 1990 Accord EX would lockup the torque converter as low as 45mph. In fact, there were a few times when I thought I could feel it lockup at 40mph but I wasn't sure, at those speeds the converter locks and unlocks are very subtle and are hard to detect.
Frankly, at 55mph I think your converter should be locking up. But maybe there's a variable range that the TCU uses to decide when to lockup, and in your driving situation it might be a higher speed. Who knows?
I hope you get it worked out, I loved my Accord. I wish they still made them the same size, the new ones are so big and heavy now. It's a pity, they don't drive anything like the older ones.
Frankly, at 55mph I think your converter should be locking up. But maybe there's a variable range that the TCU uses to decide when to lockup, and in your driving situation it might be a higher speed. Who knows?
I hope you get it worked out, I loved my Accord. I wish they still made them the same size, the new ones are so big and heavy now. It's a pity, they don't drive anything like the older ones.
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A while back I had a problem with my Accord almost constantly locking and unlocking on highway. I replaced the distributor cap and rotor just as regular maintenance (not thinking it would fix the problem), and it ended up fixing it.
The first thing I would do is check the coolant temp sensor.
Originally Posted By: artificialist
The first thing I would do is check the coolant temp sensor.
+1 and check that it is indeed coming up to temp. Maybe bad thermostat.
The first thing I would do is check the coolant temp sensor.
+1 and check that it is indeed coming up to temp. Maybe bad thermostat.
I do have consistently low coolant, as my rad has since sprung a leak. So that is in order to be fixed first.
I've noticed the check engine light and the D4 light flashes for ~2s when I turn the key to On position (just prior to starting).
I've noticed the check engine light and the D4 light flashes for ~2s when I turn the key to On position (just prior to starting).
Originally Posted By: Papa Bear
Maybe bad thermostat.
DING DING DING - we have a winner! Thanks guys for the help. Here's the lagging thermostat - opening properly but a bit slooooow on retracting. It should close in ~10s. WARNING - this is dull!
Changed it this AM and it DOES finally lock up at highway speeds.
Maybe bad thermostat.
DING DING DING - we have a winner! Thanks guys for the help. Here's the lagging thermostat - opening properly but a bit slooooow on retracting. It should close in ~10s. WARNING - this is dull!
Changed it this AM and it DOES finally lock up at highway speeds.
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