97 Honda Civic Torque Converter acting strange

I have a 97 Honda Civic EX automatic. 144,000 miles.

I drive it heavily, and I've recently noticed that the Torque Converter
sometimes will unlock at 55+ mph on the highway, and it won't lock even
if I speed up.

If I slow to a stop and the accelerate back up past 55mph, it will lock
and stay locked, sometimes.

The transmission fluid is above minimum, and it had a proper change of
fluid about 25,000 miles ago. It looks clean.

Any ideas?

 

check the coolant level and thermostat. lockup depends on the solenoid
getting signal from the engine computer - it won't send that signal
unless temperature conditions are met.

 

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Ditto to what Jim said . . . The cooling system has to be full, with NO
AIR (full reservoir cures air problems) so the computer can generate the
right signals.

Change the Z1 tranny fluid now and then too, Eh?

'Curly'

 

That's one of the first things I checked. The coolant was changed about
7,000 miles ago, and the reservoir has been at tip top.

 

There is no air that I'm aware of. Is there a trick to make sure? The
coolant reservoir has always been at or near the top.

The last time I had the Z1 transmission fluid replaced was at the
dealer, at around 118,000 miles.. after I changed out the CV axles, pan
gasket and cam gasket. Right now, the only thing this car leaks is
condensation from the A/C evaporator.

 

Oh, and the thermostat works properly. It was changed out along with
timing belt and water pump at 95K miles, at the Honda dealer. The temp
gauge works as it always has.

 

ok, but when checking coolant, look inside the radiator, not the
reservoir. if there's too much air, it can't suck back properly and a
giant air lock can remain in the system.

ignore the temp gauge for this diagnostic - it runs on a different
sensor and the needle movement is non-linear so a large temp difference
shows no difference in the gauge.

 

I looked today when the engine was cold. Coolant was at the top, right
up to where the pressure cap snaps into place.

Also, today I put about 110 miles on the car, and the torque converter
worked like a charm.. It locked at 51mph and up like its supposed to.

Sometimes it works great. Gotta love those intermittent problems.

 

i should do a write-up for diagnosing this problem some time and mail it
to tegger for hosting. right now, i have an led wired into my solenoid
circuit for this exact same situation - so i can see when the solenoid's
getting signal. so far, the solenoid system is rock solid in that the
clutch locks whenever the solenoid gets signal. but there is a problem
if that signal is not consistent.

basically, the signal goes out when the ecu believes in the car is going
fast enough, is in the correct gear and when the coolant is warm enough.
a partial [out of order] checklist therefore is:

1. check the solenoid for operation
2. check the circuitry that feeds it
3. make sure the coolant system is absolutely purged with absolutely no
airlocks
4. check the thermostat
5. check the the coolant sensor [the two-wire one under the distributor,
not the single wire one, that's for the gauge on the dash]

 

I drove it yesterday and today. It happened again. More than once.

I'm not sure if I understand about my automatic transmission having a
clutch.. I think I have a copy of the service manual somewhere. I'll
check it out this next evening.

How do I check the coolant sensor (two wire under the distributor) ?
I'll check the service manual..

I'll report back here, but it may be a few days to a week.

 

Yoww! I found my copy of the Service Manual. This thing is a
complicated beast. 4 clutches!? 2 lockup solenoids. My head is spinning.

I guess I'll start by checking the resistance of the lockup solenoids
and then I'll see if I can check the shaft speed sensors and go from there.

I still haven't found how to check the coolant sensor, but I'll figure
something out I hope.

Thanks for the help. If I figure out my problem, I'll post it.