2000 Sonata, again

I posted a transmission problem back on the 21rst of December. Thank you much Hyundaitech for your advise, yet I have to implement the solution. In short I ended up having more important issues to deal
with. Rough running, very sluggish, and odd engine revving. I've replaced plugs, wires, air filter, fuel filter, and fuel injector wiring harness that I busted when doing the plugs and wires. That has taken care of the rough idling and driving. I still have another problem, along with the ongoing transmission problem (which I will re quote at the end of this entry) after driving 50 some odd miles to or from work on occasion the engine upon slowing down will start racing and slowing down. In neutral it will rev up to 3500 and back down to 1500 only to rev back up to 3500. I have to apply the brakes to stay within the suburban speed limits. This behavior goes on and on until another re-start. I'm hoping this is related to the transmission trouble so I can concentrate on replacing the two speed sensors. I drive this car 108 miles a day to and from work, and since we paid it off two years ago I want to keep riding out the equity with as little money input as possible. It is still running very well all considering it has 124K on it and when running well I do put her through her paces. Thank you to those who tell me to take it to a competent garage, but I prefer to work and learn. When I get over my head and know it, I push the ol' girl down the street to a garage I trust.(i.e. when I don't have the tools or time)

I've been having this trouble for some time now. I could be driving at any speed when the transmission will drop down a gear and stay there. If I restart the engine the tranny will shift properly until this problem reoccurs. I have codes too. P1529, I have no idea what that one is, I was told it is a manufacturer specific code. P0720 "The PCM has determined that a malfunction exists in the electrical circuit for the output speed sensor" . P0715 "The PCM has determined that a malfunction exists in the input circuit for the turbine speed sensor." Please help this is driving me insane.
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No issue with the transmission can make the engine run abnormally fast when you're idling.
Check your throttle cable to be sure it is properly attached and nowhere coming out if its crimps. Be sure you have slack so that the throttle plate isn't held open.
Also check the wiring to the throttle position sensor and the sensor itself if you can. Rereading the trouble codes would be a good idea just to see if anything new has appeared.
Check your PCV hose to be sure it isn't developing a hole.
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hyundaitech wrote:

I stopped by autozone this afternoon to get the codes. Here is what I have P0765: The PCM has detected a malfunction in shift solenoid "D" P0760: The PCM has detected a malfunction in shift solenoid "C" . The rest of the codes are re-occurrences. P0720: The PCM has determined that a malfunction exists in the electrical circuit for the output speed sensor P1529: Scair solenoid cicuit malfunction and the last P0118 The PCM has determined that the input from the engine coolant temperature sensor is higher than expected for the current engine operating conditions (I bought a new coolant temp sensor today and will be installing it this week) So, I can assume with the work I've done has probably messed with my throttle cable. BTW, the Hyundai web site used to have a parts breakdown/ diagram. I can't find it on the hmaservice site. What am I missing? Hyundaitech, you freakin rock my socks off! Thank you for all your help!
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If you're looking for pictures of the individual items, you can find the links in the ETM section. At the bottom of the schematic, there's a link for component locations. After clicking, select the component you wish to see.
P0760 and P0765 cause me some concern. You'll want to check the TSBs at www.hmaservice.com for detailed information on how to approach these. Unfortunately, you'll need to remove your radiator to get the transmission pan off.
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