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Discussion Starter #1
I've found a few threads that describe similar behavior but there always seem to be key differences in the symptoms.

It was running fine, parked over night, and the next day it didn't want to shift at the correct RPM. It doesn't seem to matter if it's a cold start or I let it warm up, the behavior is consistent. If I slowly wrap it up a bit, it will shift. I haven't tried anything past 2nd gear for fear of breaking something.

I hooked a code reader to it and there are no DTC's whatsoever. My best guess based on what I've read is the throttle position sensor. What seems out the ordinary to me is that there are no codes at all.

Any ideas?
 

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Discussion Starter #3
I don't think it's fair of us to have any particular expectations of strangers on the Internet. I've always thought forums like this were more about being neighborly.
If someone can help I'm sure they will, it just takes time.
 

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10 Optima LX, 07 Rondo EX, 89 Chevy C1500
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It would really help if there were codes stored. Here are some questions I have.

1. Is it sluggish to accelerate, like it starts out in a higher gear?
2. Does it rev normal in park or neutral?
3. How many miles on the car and where are you located?
 

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Discussion Starter #5
It certainly would. A few months ago we had codes for misfires and replaced a couple of coils, but it has been clear since then and the engine sounds great.

I just took it out for a few blocks to refresh my memory and make sure I'm providing good information.

Is it sluggish to accelerate, like it starts out in a higher gear?
1. No, the only sense I get for the loss of power is that I stay in first gear way too long. In fact, once I'm in second gear it gets around reasonably well in-town.

Does it rev normal in park or neutral?
2. Yes, and if we could drive it around in reverse we would be all set.

How many miles on the car and where are you located?
3. Right at 29k. We're in Southeast Kansas about 2 hours from a dealership.
 

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I don't think it's fair of us to have any particular expectations of strangers on the Internet. I've always thought forums like this were more about being neighborly.
If someone can help I'm sure they will, it just takes time.
I wasn't trying to sound snippy. I agree with what you say, but at the same time I see dozens of threads with no replies. :/
 

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2009 Rio5 :)
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OK

I will try to reply here.

The throttle position sensor is not what I would say is the problem.

Directly behind the air filter box is your ECU. To the right of that is a smaller ECU, it has a smaller bundle of cables (wrapped up coming out of it). This is your transmission ECU. You can safely remove it. Remove the POSITIVE battery terminal and then remove the transmission ECU. Do not wear gloves and keep one hand on a metal car part at all times. Yes you are grounding yourself. If you have trouble getting it out (think it has 2 screws) then you need to stop. Do not bend, twist, force, or manhandle the thing. it has a chip board inside that you won't hurt, but if you bend the million little prongs though... not good.

If you get it out.

You can take the cover off. Visually inspect for damage, see if there was a power surge like when you had coil problems. Melted plastic, smoke, burn marks etc. time for a new one. Probability 20%

Next up.

There are a couple of sensors that could be the culprit. Follow your transmission dipstick. Directly to the right (facing engine) of the little metal bracket that holds the dipstick in place is the transaxle range switch. This one take quite a bit of skill to replace so be very careful. It has the job of telling the ECU exactly what gear you are in at any given time. It is that thing that locks out reverse while driving and only allows starting in park and neutral, but if it thinks you are in second gear already, or that you need more RPM's for passing it could be the problem. Probability 15%

All the way at the base of the dipstick (just to the right) is the solenoid control connector, the solenoid is inside the tranny. It has the wonderful job of merging hydraulics and electronics to send tons of glorious data to your tranny ECU then translate the responses into actual shifts. I am willing to bet this is where your problem lies. Now it could be sending wrong data, interpreting data wrong, or the ECU might be the problem. Probability 65%

What I would do is start with the cheapest, then go from there.
Check the fluid. Make sure it does not smell burnt, and is at correct level.
See if you can check the tranny ECU.
Make sure your transmission is properly grounded. Top, middle, bottom, sides, everywhere.
Unplug the solenoid control connector test the different terminals with a volt tester (not sure if you will get anything because it uses both hydraulic and electric but continuity might work).


Then it's time to change the solenoid control switch. This unfortunately is what I think the problem is. It is not really easy to get to, and not real easy to change. I will see if I can find a good guide somewhere, and I'll post it here, but tranny folks are like a cult. They don't like to share their secrets so they can charge the crap out of us.

Check the rest, and let me know. Cheers.
 

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Discussion Starter #9
This just kept getting more and more strange. After reporting no loss in power I started experiencing a loss in power while test-driving. It finally threw a misfire code and we had to replace a coil. Once that was out of the way we disconnected the negative terminal for a few minutes to reset any shift memory.
This made a huge difference but it still wasn't right.

On a cool morning it would shift wonderfully and then start getting rough as it approached operating temperature. It would eventually level off at what I'm guessing is a failsafe scenario (3500rpm + some other sensor inputs)

After getting some detailed technical specifications we removed the outgoing speed sensor mounted on top of the transmission and tested it. It was in great shape and clean, but tested 600 ohms instead of the 245 it was rated for.
I have one on order and should know something next week.

Thanks for all the input!
 

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Discussion Starter #11
The sensor arrived and we replaced the old one.

At this point I feel like we're troubleshooting a completely different problem. I'm sorry that some of this information seems inconsistent, but I'm just reporting what I observe and that changes as we fix things we find along the way. It's like the thing decided to fall apart once it was safely out of the basic warranty period, not that I could limp it to dealership if I wanted to.

The behavior is different with the new sensor but still not right. I found the procedure for setting up the shift memory from kiatechinfo.com and we took it out to see if we could get it working.
Using an ODBII tool with a live data feature we tracked the TPS % so we could follow the instructions to keep it at 30% and go through shift cycles until it started to shift smoothly.
At 30% throttle it shifts pretty well and we were able to get it shifting smoothly, but it was very slow to accelerate and we weren't able to get it over 50mph with the pedal to the floor in 4th gear (it started to chug at that point but stopped when we slowed down). The TPS showed 85% floored, but that might be normal behavior. It was around 5.8 idling.

My dad has been helping me with it and he suspects that we might have a fuel flow problem of some kind. Of course, checking fuel pressure requires a special attachment and the fuel filter is an in-tank assembly that runs upwards of $200.

There are still no DTC's being set. We got the misfire and replaced a coil and while experimenting with that sensor we got a sensor failure by disconnecting it completely.
That code was cleared after we installed the new sensor and no other codes have been set since.
 
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