Transmission acting strange, TCU failing?

[AhYesCB7]

So this morning while driving to work my 93 SE auto acted a little odd at around 70-80 mph. It felt as though it was dropping out of 4th gear for a few seconds at a time. I would be cruising and the rpm would shoot up a few hundred and then go back to normal when I let it slow down a bit. It only seems to do it above 70.

I must admit I bought this car and put about 12k miles on it and only just checked the tranny fluid this morning at work lol.

The car has always been a little odd since you can give it a hair of throttle and it'll rev up to around 3k rpm before it will change gear. I always found that to be wrong but it always drove smooth. Shifts are "hard" sometimes but no banging or clunking. Just bad motor mount in the rear I'm thinking.

Fluid is brown with a tinge of red left and doesn't smell totally burnt, seemed to be full. After driving home and cycling all the gears before shutting it off, the fluid is slightly above the hash marks on the stick.

I'm thinking the TCU is about to shit the bed. Maybe a clogged solenoid? I'm gonna run out and get a few quarts of Honda fluid but I'm curious if my symptoms are ringing a familiar bell.

[Rilas]

By a few quarts I hope that you are meaning roughly 9 quarts.... To drain and refill these transmissions properly you need to do 3 flushes and 3 fills with a bit of driving in between them. This will flush out almost 90% of the fluid in the transmission. I'm guarantee that this will improve the shifting and feel of the transmission. Although at this point it might be too late and the clutch packs might be on their way out. Also you should take your solenoids off and clean the screens on the gaskets. They have very fine metal screens built into the gaskets, they collect metal and clutch material. These could be making it hard for the solenoids to get the job done.

[AhYesCB7]

I took the car for a spin to go pick up a few things. Car drives "normally" through the city and when I took it on the highway it didn't do what it was doing earlier so I'm thinking an electrical issue is cropping up.

I plan on taking out the TCU and inspecting it, probably gonna get the rebuild kit and so some soldering. Definitely gonna drain and fill it a few times to get that old shit out of there and see how it feels.

I didnt realize the shifting is partially controlled by the throttle cable and TPS so I was wondering if the TPS developed a dead spot? Gonna look at the cable tension to see if thats why it shifts kind of laggy.

Ill have to see how she acts in the morning, but it didnt do it just now so I dont think its a serious mechanical issue. The trans doesnt whine loudly and the lights arent out of order on the dash.

[AhYesCB7]

And I should add that it only seems to shift lazily when you're barely on the throttle, if you're a little more in it the shifts are firm and the power is there. Its been happily cruising about for the past 12k miles and thats why todays little hissy fit has me curious.

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I'm now thinking I was feeling the ignition system acting up maybe? I noticed my coil wire has swelled from contact with the valve cover right near the coil. I've been meaning to do cap rotor and coil soon as I'm guessing its original to the car. I've always wondered if the plug wires in general were bad but never really looked into it. I have a set of 9.3mm wires I'm going to install when I fix the tube seals, gonna have to fix that coil wire now too.

[oni_cb7]

The ignition system would not make your car shift weird. Especially with what you've described.

The TCU would not affect it in this way. If there was an issue with the TCU, it would throw the car into limp mode and restrict the gears that you can use. My TCU needed to be replaced and threw itself into limp mode. I could only use 1st and 3rd during this time.

At this point, the only real advice to give is exactly what Rilas said. Drain and refill the auto trans three times with driving in between. At best, this may delay your transmission from going out on you. But, it does sound like your transmission is on its way out. As a note, transmission issues are not a catastrophic failure right off the bat. They give a lot of signs that they are beginning to fail. Slipping like you described is almost always caused by old fluid not lubricating correctly. This also wears out the clutch packs and can cause the gears to slip slightly. Eventually, the trans will just not be able to go into that gear any more and simply free-rev as if it is in neutral.

Good luck

[Fleetw00d]

What you're feeling is the torque converter locking and unlocking. Particularly noticeable in 4th gear (and with cruise on), on level ground and going downhill, the torque converter will lock up. When accelerating some, or going uphill; the torque converter will unlock and engine rpm will jump about 300 rpm for more power (if you really push the throttle or it is a steep hill, it may drop to 3rd).

With the throttle closed; there should be no slack in the transmission throttle cable with the lever on the transmission all the way down. The cable can be tightened up to 2 turns to effect how the lock/unlock works.

As others have suggested, change out the fluid (3 drain and fills with driving in between). Then take it on the highway and pay attention to when it locks/unlocks. If it operates backwards (rpm increases on level or going downhill, decreases - at least initially - when going uphill); then tighten the transmission throttle cable by a half turn at a time until the lock up works correctly (2 turns max).

If there are no transmission codes; I wouldn't condemn the TCM yet. The two that I've had go bad have thrown multiple random codes before giving up. I've had two TCMs successfully repaired by "mandigital" on ebay; lifetime warranty.