1990 Honda Accord LX Tranny Lock-Up Problems

Greetings! I'm new to this site and I'm looking for help with my 1990 Honda Accord LX. I have a automatic tranny with a 2.2 L 4 cylinder. The transmission is not going into lock-up when at cruising speed. In D4 my tach is reading about 3100RPM at 70mph (is this normal?). Every once in awhile I will notice that the lock up will engage and it will drop my RPMs by 100-300. Does anybody have any advice on what could be wrong? I don't notice any engine lights or anything like that on in the car. The car has 162K miles on it. Other than this problem it shifts great and runs good. I have noticed my gas mileage has dropped a little bit because the lock-up is not engaging. Does anybody know any troubleshooting advice for the Lock-up assembly solenoids on the outside of the transmission? Any advice would appreciated!

Regards

I can't give you specific Honda advice, because my tranny experience is limited mostly to domestics.

That being said, it's a very common problem on GM's, except that rather than not applying, they tend to get stuck and cause the car to stall as you come to a stop. I'd prefer your problem to that any day.

The solenoid's operation is very straightforward, it's either on or off. The powertrain module decides when it should be locked, and energizes the solenoid.

If I were looking at your car, I's probably find a place to tap into the wire that energizes the solenoid, and set up a test lamp inside the car. If you go to the library, and if they have Mitchell On-Demand or a similar online manual, you can look up the location of that wire as it comes off the PCM (referred to as "pin-out tests") and it will tell which terminal is for that, and what conditions it should be active.

If it is too hard to access, you could do the same thing just tapping into that wire near the tranny, and running a test lead to your test light or meter inside the car. Then drive and make sure it commands a lock at the appropriate times, and that the signal is consistant.

Once you verify that the command circuit is operating properly, you move to the possibilty that the solenoid is defective. Most of the ones I've replaced in Asian trannies were inside the pan, fairly easy to access from under the car. The GM's are in the side cover, and require removal of driveline supports and lifting of the motor/tranny for access, kinda sucks. You'll have to see what the procedure is while you're looking up the pin-out tests.

It's pretty uncommon (as far as I know) for the actual lock up mechanism in the convertor to fail, but it's possible, I guess. Maybe someone here knows if that's happened in Hondas much...

I like to experiment, if it were my car I might be tempted to simply supply a 12v source to the solenoid wire with a jumper, and use that to lock it up manually, to see if it holds, then I'd know that the solenoid and mechanism were ok, and the problem was in the control system. But that's not "proper" repair procedure. I'll guinea pig my own cars, but not other people's, so that's up to you...

Thanks for the advice. The lock-up solenoid assembly is very accesible and is located right on top of the transmission. It has two solenoids, (not sure why two) but like you said I could disconnect the electrical connection and string a wire to a test light inside the car and then drive the car and see if the computer is sending the signal to the solenoid assembly to lock-up. I bought the car in Sept 05 and it worked when I bought it, but I noticed that the problem started to be intermittent. Then it just quit working. I was gonna try and find a lock-up assembly at a local junk yard and just replace it and see if it fixes the problem. I called a dealer to order a new part and they want $160 for it. Not worth it to me. The only thing I'm concerned about is that is could damage my trans since it is not going into lock-up and probably heating my fluid up higher than it is supposed to be.

Just a thought, but perhaps the Tranny Control Unit. In older model accords, they have a tendency to go bad. This usually causes a blinking d4 or S light. It is covered in the FAQ though. Easy to replace (under passenger kick panel) for about $50 at any junkyard.

I thought of that, but since he didn't mention the light I didn't think that was the problem, I've read where you guy's cars do that when the controller goes out. Still could be demented and not self-diagnosing, I suppose, that's why I suggested using s test light to see if the controller was commanding lockup appropriately.

I had roughly that behavior with one of my Accords. It's probably not right (indeed, I didn't see it on my other Accords), but posting my question here only came up with suggestions that it was downshifitng (whcih it clearly wasn't). I learned to ignore it, and in 60,000 miles or so it never changed behavior. 3100 rpm at 70 is about right, though.