1992 Accord 4d LX auto- 215k miles- about 2k miles on fresh Honda DW-1 ATF in the trans

Hi guys, new guy to the forum here. I've been scouring for an hour or so on this forum trying to find some insight on what's going on with my accord. I've found several instances but none have any real "fixed" outcomes that I can see, and I'd like to know if anyone has had any success so I have a better idea of where to start troubleshooting.

Issue: While cruising down the highway at 80 mph, the engine will run 3k rpm even. Once I let off the gas, or the cruise becomes passive on a flat or slight downhill it seems to downshift slightly and run about 3200 rpm. This wouldn't bother me if it didn't also do this with steady throttle on a straightaway every 10 seconds or so. It seems to be overactively engaging and disengaging the torque converter lockup from what I've been reading. This thread sums up my problems pretty well:
https://www.hondaaccordforum.com/for...problem-47475/

Some threads point towards the converter lockup solenoid, others the throttle linkage to the trans, the coolant temp sensor to either the ECU or TCU (Idk which, or why), and some all the way back to the TCU itself.

I'm capable of testing solenoids, sensors, and circuits on the TCU but I'd like to see if someone point me in the right direction before I go troubleshooting. I've got a garage to finish building, and a 2 month old baby to tend to so time spent working outside of work is scare at the moment. Any insight that would help speed up the troubleshooting process would be greatly appreciated.

 

I think first check for error codes in the ECU or TCU. Short the SCS connector & watch either the check-engine light or the D4 light flashing. There's more information about that in a sticky thread up at the top. Any error codes will point you in a better direction than us guessing.

Unfortunately, the thread you linked is like so many others where the original poster never comes back to tell us the end of the story.

The couple things you mentioned to check would be pretty easy to check visually without throwing parts at it.
- Throttle linkage to transmission. The lever at the transmission should begin moving just at the same time as the throttle begins to open. The cable from the accelerator pedal to throttle should have slack, but the cable down to the transmission should be just right at the point of going slack.
- Coolant-temperature sensor is screwed into the end of the cylinder head, with a 2-wire connection. Just look for obvious stuff like loose wires unless you see an error code actually pointing to that sensor.

People have had the lock-up solenoid get plugged with crud, and had success cleaning it out. I think it takes a bad wiring connection for the TCU to flag that specific error code.

Disclaimer... I'm not much of an expert on automatics, hope other chime in.

 

Thanks for your reply, once I have the chance to check for codes I'll post what I find. No error lights or flashing lights have come on so far so nothing is obviously wrong there, but I'll see if there are any possible stored codes.

I'll take a peek at the throttle linkage like you mentioned, that's indeed a good troubleshooting item taking minimal time/effort.

Which end of the head is the coolant temp sensor? I've read it has two, one for the dash cluster and one for the computer, is this the one for the computer?

If I don't find anything there, I think the lockup solenoid is right on top of the trans, does that sound right? If so maybe it wouldn't be too much work to take it off, clean it up, and check that it works properly.

Thanks for your input, I'll start there and work my way into it.

 

No codes to display.
I didn't check the wiring back from the lockup solenoid but the solenoid itself works when 12v is applied.
The throttle linkage is slack free to the trans.
The temp sensor wires look ok, although I'm unsure as to what the temp sensor would have an effect on regarding the torque converter locking up.

Would the next step possibly be at the TCU?

 

There's 2 temperature sensors in the head near the distributor. Right side of the car.
The one with 1-wire is for the dashboard gauge. The one with a 2-wire connector is for the ECU.
I think the auto-trans is programmed to not lock-up the TC until the engine temperature gets to a certain point.
If the temperature sensor wiring is flaky, I think it should throw a code 6 at the check-engine light.

Not to take anything for granted... There's a silly little "performance chip" you can buy, and plug into the wire from the engine temperature sensor. It changes the signal to make the ECU think it's colder. If you have something like that plugged into the wire for that sensor, remove it to see if the TC lockup problem is caused by spoofing the engine temperature.

Make sure your check-engine light comes on for 2 seconds when you first turn on the car - that's the bulb check. Also make sure you have a bulb in the D4 lamp on the instrument cluster. Certain Accords (I'm not sure which) have a "sport" switch for the auto trans, in that case it's the "S" lamp that does the flashing for error codes.

 

I didn't notice any additional chips or add ons at the temp sensor, but I'll take a second look for that specifically.
There were indeed bulbs present in both the CEL and D4 spots.