I love my 94 but can't stand the computer relearn process (2 Viewers)
- Thread starter Kkxrw
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- Thread starter
- #22
I will double check the iac mine is 2 years old. Thanks
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Malleus
Far west of Siegen
?
- Thread starter
- #24
Sorry. Typos I will double check the iac mine is only 2 years old. Thanks
Malleus
Far west of Siegen
Make sure you do both tests. Mine passed the initial test, because the stepper motor still worked, but it wasn't until I removed it that I could verify the plunger wasn't moving. Also, make sure you note where the motor is when you remove it. You need to put it back in the same position, or the ECU won't know where it is.
It's not the end of the world, however; you just need to pull the ECU MAIN fuse to reset it. This clears all the stored sensor positions/states and forces the ECU to record the current positions/states. Disconnecting the battery does the same thing, it's just more work.
Unfortunately, that's the only single point failure I can think of, at the moment. If that's not the root cause, you'll have to go through the long troubleshooting process.
It's not the end of the world, however; you just need to pull the ECU MAIN fuse to reset it. This clears all the stored sensor positions/states and forces the ECU to record the current positions/states. Disconnecting the battery does the same thing, it's just more work.
Unfortunately, that's the only single point failure I can think of, at the moment. If that's not the root cause, you'll have to go through the long troubleshooting process.
Are you positive? I've been dealing with this s*** too on my 94. Same thing, disconnect battery to upgrade to a new one, ever since been idling like complete ass. No cold start idle, basically turn the key, and it idles well below 1,000rpm. I've never owned a toyota or lexus that didn't have cold start idle. I went nuts trying to figure out the issue, the car sits in a shop and hasn't seen teh road in years as I am basically doing a full build. I have a new IACV, TPS, and a few other things I will try replacing this winter to see if it fixes it.
I replaced the intake tube with a new one, no changes, replaced the throttle cable with a new part, no change. I guess I'll keep hunting it down.
All the research I've done here, there are countless threads that mention these vehicles do have a "relearn" process or whatever that crap is called. Conflicting reports as to how long this process takes, how many times you have to start/shut the engine off, how many miles you have to drive, until it's back to 'normal".
That's why I am surprised at how confident you're saying there is no such a thing.
- Thread starter
- #27
Well I checked my IAC and it tests out correctly and looks like it's working I still can't figure this out
to be clear
it idles okay It doesn't high idle anymore it bogs down until it's fully warm when I put my foot on the gas
to be clear
it idles okay It doesn't high idle anymore it bogs down until it's fully warm when I put my foot on the gas
CharlieS
GOLD Star
I get a flavor of this too, and haven't been able to figure it out. Sorry for no help, but I can commiserate with you. I'm happy about idle, running when warm, acceleration when warm, but when cold, I have a spot in the bottom range of the acceleration below 2500 rpm that kind of bogs down before the rpms go up, it feels powerful and it goes well again. I've replaced pretty much anything you can name for preventative maintenance and troubleshooting. Most recently TPS replacement and adjustment made the biggest improvement, but it isn't quite there. Now I just live with it.
- Thread starter
- #29
Thanks. I went through the same process. I have replaced so much on this truck. There has to be someone on here that solved this issue
- Thread starter
- #30
Mine hesitates in that RPM range also. Only when it's cold once the truck is fully warm it doesn't do that anymore
Malleus
Far west of Siegen
Well, if both tests check, then, without resorting to the full spark/fuel troubleshooting procedure, I'd check the AFM circuit. I doubt it's fuel, because it runs well sometimes, and the fuel system tends to be stable; it either works or it sucks. Those are the two usual suspects, anyway.
Failing this, you're in for the full Monty. You'll have to start with the air intake and go all the way to the valve, and then go to the fuel system if that doesn't pan out. Along the way, you'll be checking various ECM cirnuiots, so you'll get a good look at the entire air/fuel system, before you're done. Fortunately, the FSM troubleshooting section is fairly robust, and the systems are straightforward. Be glad this isn't a 100 series. The diagnostic section is 1000 pages long.
Malleus
Far west of Siegen
Yes, I'm positive. If you read the service manual, you'll come to the same conclusion.
There are many people who, not having formal engineering or mechanical training, will assign meaning to observations, when there are no valid reasons to do so. Though well intentioned, these assumptions, stated as fact, do not become facts, simply because they are stated as such.
Malleus
Far west of Siegen
@jonheld and @cryorunner are far more knowledgeable about electronics in general, and 80s specifically, than I am, and I'd gladly defer to their opinions on the matter.
VAF
Malleus
Far west of Siegen
That's what I meant to say...
- Thread starter
- #36
Thanks but I tried that too. bought an extra vaf off of someone on mud that rebuilds them and another off ebay. All of them operated the same way. You name it I replaced it in the last 2 years
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Malleus
Far west of Siegen
I got nothin'...other than break out the book. FWIW, I may be interested in taking those spares off your hands.
- Thread starter
- #38
I appreciate your help. Thank you.
COS80
SILVER Star
I can't really argue one way or another, because I'm new to this platform, but many other platforms, a relearn process is a part of the factory ECU program. The ECU zeroes all parameters when the battery is disconnected, and then when reconnected, it readjusts certain parameters, like spark advance curves, based on others, like throttle position, in order to optimize itself for driving style and ambient conditions. Does this one do it? I can't say, but I can tell you my '97 idles very low, every single time I disconnect the battery, and then slowly corrects itself over an hour or so... seems like an ECU relearn to me.
Can you please post who rebuilds 93-94 VAFs on Mud? I remember someone mentioned there’s an eBay seller that does it a while back.
