My 1994 truck ran great. I disconnected my battery to change the alternator. Now the ecm relearn process is in effect. It has been several weeks and runs like s*** when cold. This was not the case before and I am certain it's this damn relearn process. What is the secret to the relearn process? How many times does she need to start, miles driven, time, AC on or off, etc? Thanks
I love my 94 but can't stand the computer relearn process (2 Viewers)
- Thread starter Kkxrw
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Malleus
Far west of Siegen
There is no relearn process. The ECU isn't programmable.
Malleus
Far west of Siegen
Just a thought, have you checked for engine malfunction codes?
- Thread starter
- #4
I was told there is with 93 and 94
- Thread starter
- #5
None
Malleus
Far west of Siegen
Nope, not on any 80.
Malleus
Far west of Siegen
You might want to download a copy of the Toyota service manual. It's in the Resources section. Very handy.
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- #8
I have a copy and did not see anything
Malleus
Far west of Siegen
Does it run well once it warms up? Running poorly after warmup or, conversely, running poorly when cold and well after warmup, may be a sign of a stuck IAC valve. It operates like a choke on a carburetor.
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- #10
I see some threads that say ecm needs to relearn sensors. ODB1. As an example
Post in thread 'Battery reset, then high idle, then low idle' Battery reset, then high idle, then low idle - https://forum.ih8mud.com/threads/battery-reset-then-high-idle-then-low-idle.805221/post-9189991
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- #12
Yes. When it is fully warm runs fine
Malleus
Far west of Siegen
Check the IAC valve. Page EG-294:
Malleus
Far west of Siegen
I think the battery disconnect and poor engine performance is coincidental. I can think of nothing that disconnecting the battery would do to cause your problem.
Malleus
Far west of Siegen
Malleus
Far west of Siegen
The IAC valve is a stepper motor driven plunger that opens and closes the bypass air galley to the throttle body. If it's in the wrong position, engine performance will be seriously degraded.
If yours fails either of the two tests, try disassembling it and cleaning the plunger bore. Some have had success with this; I did it and it worked for a awhile, but then failed again. You can try a used IAC, they don't fail often, IME. @slow95z can hook you up.
FWIW, the '93/'94 IAC is no longer available, but the '95-'97 valves are, and they are direct replacements.
If yours fails either of the two tests, try disassembling it and cleaning the plunger bore. Some have had success with this; I did it and it worked for a awhile, but then failed again. You can try a used IAC, they don't fail often, IME. @slow95z can hook you up.
FWIW, the '93/'94 IAC is no longer available, but the '95-'97 valves are, and they are direct replacements.
Malleus
Far west of Siegen
"Relearn" is a misnomer. The ECU is has to obtain new operating parameters from a few sensors; this is something the ECU does while the engine/transmission is running, too. That's not relearning, IMO, but I won't argue the point.
I don't think this is your problem. The IAC, IME, is the common cause of poor performance, when no codes are present. There is no ECU signal for the IAC position relative to engine temperature, which is an oversight, since one depends on the other. Toyota apparently never considered the stepper motor plunger would get stuck.
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And it was running well before and now it's not. Make sure you didn't knock something loose during your preventive maintenance.
Malleus
Far west of Siegen
...another possibility.
