I have a 1998 Lincoln Continental. It has 124k miles on it.
The history of the transmission maintenance are as follows:
Fluid and filter was changed at 29k miles Fluid was flushed at 86k miles Fluid was changed at 115k miles
All with Mercon V Motorcraft
All old fluid was in normal red color shape. Not brown, black, or burnt odors.
At 122k, I started experiencing delayed engagement from park to drive during cold weather starts. Letting engine idle for about 7 minutes stopped this from happening.
123k, while on hwy, "check transmission" warning light popped up. But vehicle drove normally. After I exited hwy, I went to autozone and had them pull malfunction code. It was p1744. TCC Stuck in Off. They reset code.
Next day, had pan dropped. Filter changed. Fluid changed again. Magnet had average wear. No abnormal stuff in pan, on filter, or on magnet.
Drove car for 14 days and on hwy, on several occasions. Warning never popped up during that time.
124k, while on hwy. "check transmission" warning light popped up again. Got off hwy. Had code reset. Got back on hwy. Warning returned again. 200 mile trip. After I exited fwy, vehicle was shifting a little rough. Car temp gage did not overheat. No fluid leakage.
Pulled code. Same p1744. Checked fluid. Fluid was red like new fluid. No burnt smell. Fluid level was checked in park and right after I exited hwy. It was in hatched area like manual suggests.
Drove home later that day with same warning lights.
Checked transmission (solenoid valves/temp) connector that is on top of transmission. Inside pins, it was full of tranny fluid. Cleaned it out with electrical cleaner. Added di-electrcal grease to connection.
Started car. Ran normal. Shifted into drive or reverse, the rpm fluctuated consistently from normal idle to halfway below idle. It does this for about 3 or 4 mins. Sometimes longer. Other times it stall engine.
But if I just accelerate pass the normal idle RPM, it drives normal. However, once I come to a stop and it goes down to normal idle, it does the whole up/down/up/down/up/down idling fluctuation, consistently from normal idle to 1/2 way below normal. It never goes about normal idle and it never goes below hallway normal idle.
I took vehicle to first repair shop I saw. They said it was Idle Control Motor. I told them that car idles fine in park and neutral. They claimed that if it didn't fix problem, they will refund money. They replaced idle motor. It did same thing in drive and reverse. I made them remove their idle motor and replace my old idle motor. They did and returned my money.
Then I went to autozone and disconnected transmission (solenoid valves/temp) connector that is on top of transmission. It had atrace of tranny fluid in there. But you would have to look close to actually see it. I started car. it idled normally. I shifted it into reverse and drive, Codes p0755, p0743, and p0750. I had a autozone guy pull the codes. Those codes were expected since I disconnected transmission harness connection. I shifted into drive and reverse. It shifted normally into those gears and idle was normal. Codes were erased. I then turned off car and reconnected transmission connector.
I restarted car. Put in drive and reverse. It did the same up/down/up/down rpm fluctuation. I drove car home. It drove normally. But does the same thing when at a stand still while in reverse and drive.
What can be the problem?
Torque Convertor Clutch? TCC solenoid? Anything else?
Repair places keep saying idle speed motor. But that was already checked.