94 Accord torque converter in and out

My 1994 Accord seems to do something strange at highway speeds. It
seems that the torque converter is locking up and unlocking
repeatedly. I try to maintain a very steady speed, but I'll feel it
unlock and watch the tach jump up ~250 RPM, then watch it drop it back
down again. This will happen on flat road, but very much more so on a
slight (and I mean slight) incline. If I use cruise control, the
problem it's so bad, but still present. It seems like it's more
sensitive than it should be. It'll just as much as every 5-8 seconds,
especially if the road isn't perfectly flat.

Otherwise, the trans seems to shift fine. Shifts a little rough,
especially when it's cold, but nothing to really complain about too
much. I did a trans fluid change, but I didn't use Honda fluid
(changing again this weekend w/ Honda fluid after what I've read about
that).

Can anyone give me a recommended adjustment I can make? Could it be a
bad TC solenoid? Or is this just a standard Honda auto trans? It's
the first one I've owned.

About 140k miles, no check engine light.

Also, I've noticed two distinctive clunks when I put the car in drive
from park, especially when it's cold. It's almost as if it's a
two-part shift process. There's a slight delay between the two.

I'm trying to take it easy on the car. I just bought it, and I'm
afraid of any trans problems coming up already.

Thanks
Gregg

 

--------------------

The non-Honda fluid explains everything you described, probably.
Especially the really solid shifts. The short delay is famous on
Odyssey, but might get better after drain-n-fill. You'll have to do a
second drain-n-fill later, and be sure to do both of them when tranny is
warmed up, so you get a higher % of the crud into suspension. Let it
drain several minutes, then, if you want to be thorough, start the
engine for ten seconds and 'pump' out the converter by putting it into
reverse / D4. You'll get almost another quart out.

Some won't agree with that last part. . . . 'Curly'

P.S. Always mention your mileage :-(

 

Disclaimer: Much of the information I pass on is speculation, based on my
experience with Honda transmissions. My experience includes 8 years building
and rebuilding Honda torque convertors, 6 years of
building/analyzing/rebuilding Honda automatic transmissions, and 10 years as
owner of Honda Accords(currently 5). Please use this information for
reference only.

Hi Gregg:
I also have a '94 Accord that my daughter drives and I have had that
same hesitation at initial takeoff for over 100,000 miles. It's annoying and
unsettling, but I don't expect it's gonna get any worse. I have always used
genuine Honda ATF, and kept it changed at about 33k miles. No other
transmission troubles, and that car is approaching 175 k miles.

I don't believe the two symptoms are related. The trouble with your
lockup function is probably electrical; either PCM or external solenoid. I
don't remember which solenoid(s) control lockup on that model year, (later
models use a shift solenoid and linear solenoid to control lockup function)
and I'm not advocating that you start swapping them out. It seems to me that
the T/C shifting in and out of lockup wouldn't be caused by defect in the
T/C though. If the friction disk on the lockup piston were worn the slippage
would probably be so subtle that you wouldn't see it a s a shift in and out
of lockup. If it were worn badly you would probably experience a jerk when
lockup was achieved, but once locked it would stay locked until electrically
shifted out again.

If you really have concerns about gunk in your fluid, strain it through
a paint strainer after you drain it. Chances are you would find any
significant solids in it, especially if you are changing it regularly(30~35k
miles). Also, check it for a burnt smell; that might indicate that something
has been excessively hot. If you do find much in the way of particles, then
you might as well plan ahead for a transmission swap in the distant future.

I wonder if it's worth the effort to completely drain your ATF. The
solids in the ATF have to be awfully small to pass through the strainer, so
I wouldn't expect very much to be suspended in the oil. You have at least
two magnets in there to collect ferrous material(one inside and one in the
drain plug), a strainer with media that has about a 50 micron mesh(I think),
and numerous screens in the hydraulic path to capture potentially
troublesome particles in the oil. Changing the ATF isn't going to remove or
even disturb these trapped particles anyway. Much of the fluid that does not
drain is kept in the torque convertor, and the T/C check valve is what keeps
it in. That fluid has not settled in the T/C; oil flow through the T/C is
very aggressive and there is no settling going on in there. It even has
centrifugal filtering built in so it captures solids as it turns.
I find it hard to support the recommendation to run your
engine/transmission when you have the drain plug open. ATF is lube oil as
well as hydraulic fluid, and if your running your transmission through gear
ranges with no fluid you have clutches(probably 1st, potentially all)
running dry, gears meshing(oil pump, idle gears, drive gears) and bearings
(shafts, case bearings)turning without the lubrication that was engineered
in. Inside the torque convertor there are bearings(on stator assembly) and a
friction disk(lockup clutch) as well.
The question is how long can they run while dry, (or at least while not
immersed in ATF), before damage results, and I do not have that answer. I
suggest that if you are going to run the transmission without ATF in it, do
not do it for any length of time beyond what Curly recommends. With all due
respect to Curly; he may very well have experiences that I don't.
Doc
PS: Use genuine Honda ATF. These transmissions were designed around it's
use.

 

I think this is normal, my 87 does this. I read if there is a slight load on the motor, it will lock up the converter. On level
or downhill, mine jumps up a hundred rpm's. Going slightly uphill, or if i give it a little bit of gas,the converter will lock up,
dropping rpm's slightly.

 

Gregg Gruen says...

I too have a 94 Accord, and had a problem with the converter
working sometimes, but not others, but I didn't have the
short-term switching you seem to have.

In my case it turned out to be a temperature problem, not a
transmission problem at all. The computer will allow the TC
to engage only if the engine is FULLY warmed up. When I
changed out the thermostat, that fixed it.

In retrospect, though, I think there is a chance that the
cooling system just needed to be bled of air, so that the
coolant temperature sensor stayed fully immersed. I
started having problems after the coolant was drained and
replaced at 30k miles, and my guess is that the system just
wasn't bled fully. Anyway, I DID bleed it properly with the
new thermostat, and it's worked fine ever since.

This is going back several years, so I don't remember all
that well, but someone here told me how to do an important
test to see where the problem was. There are two solenoids
on the transmission which control the lockup converter, and
each of them is controlled by a pair of wires. I soldered
a straight pin to the end of each wire of a length of
regular four-conductor telephone line, and inserted the pins
down into the control line connectors so as to make contact,
and then brought the phone line into the passenger
compartment.

Then you can read the voltage across each control pair with
a volt meter, or hook up an LED across each pair in series
with a few hundred ohm resistor. When the computer is
trying to engage a solenoid, the voltage across that control
pair will go high (up to 12VDC), and your LED will light up,
but the voltage will be low otherwise.

As I remember, it is a three-stage process as your speed
increases. First one LED comes ON, then the second one
comes ON, but it flutters, as though it's only ON half way.
And then it goes solid ON when the TC is fully engaged.

The idea is to find out whether the solenoids are not
getting the control signals to turn on in the first place,
or whether they are getting the signals but are not engaging
properly. In my case, I found that the signals weren't
being sent in the first place, which pretty much locked down
the coolant diagnosis.

Your problem probably isn't the coolant, but you still might
want to make that test. There's no point farting around
with the transmission if the problem is with the control
signals not staying on.

Hope this helps.

 

Thanks to everyone for all the good info. I did the fluid change this
weekend with the Honda ATF, and I've already noticed an improvement in
the 1-2 shift. The outgoing fluid was fairly clean. It didn't smell
burnt. There was a thin layer of particles on the drain plug, much
less so this time than the first time I changed it. (bought the car
at about 133k, first change was directly after that. Nearly 140k
now.)

One thing I noticed today when I took it out on the highway was that
darn TC again. This time it wouldn't engage at all. I drove for
about two miles at about 68mph on flat highway and it wouldn't engage.
I got off, turned around and tried it again and it seemed to work ok.
I'm beginning to suspect something, but I don't know what. I've read
some about the TC solenoid, and I've found two on the transmission. I
might do a bit more research on those to see if I can determine
whether one might be sticking.

Thanks again,
Gregg

 

TC lockup doesn't work until the car warms up.

 

I have a similar problem, but in cold weather. I'm certain my
thermostat isn't closing all the way. When the temperature is below 45
the engine doesn't warm up enough for the LTC to engage.

Also, the LTC engaging and disengaging was bugging me shortly after I
purchased the car and was able to fix the problem by adjusting a cable
that runs from the throttle to the transmission by the radiator. It
should be tightened so the slack is taken out of the cable with the
throttle closed, but no more. Play around with it a bit and you'll
probably get what you want.

 

It turns out the problem was temperature related.

I did some digging on this newsgroup and spent a few days thinking
about it, and decided that it might be temperature related considering
I noticed the problem the most on a really cold day. I did a little
experimenting doing about 70mph down the highway with the temp control.
On hot (heater core valve open) the TC unlocked every time. If I
flipped it to cold (valve closed) it would usually lock up within 1-2
miles. I did this 5 or 6 times to confirm, and in every case it did
exactly the same thing.

I bought and installed a new thermostat from a dealer, and the problem
seems to have gone away. I've done one road test so far with excellent
results. If anything, it locks up better than ever. The old
thermostat looked different; I couldn't tell if it was aftermarket or
not. Both were 78C thermostats. I know the last owner had most
everything done at a local mechanic, so it's probably safe to assume it
was an aftermarket part.

 

spigot says...

Congratulations on your fix. Sure was a lot cheaper than
all the other possibilities.

How many trips, and how much money, do you think would have
been required to get a dealership to fix it?