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I've got a 2005 Wagon. I recently had to rewire the harness that goes from the car to the lift gate because the wires were cracked/melted and it was shorting my stop lamp circuit.

I've only had the car for a little over a year and so I took the battery cover off and noticed an INSANE amount of corrosion and foam around the contacts. It took some serious work getting the cables off. I cleaned it all up.

After finishing soldering the dozen or so wires back together and getting everything to work (even my rear wiper that hasn't worked since I've had the thing...yay...) I started it up and let it run for a bit. I noticed it idles SUPER low now compared to before I took the battery off. I read on FF that it re-learns how to idle after losing power to the ECU for more than 10 minutes.

So my question is, why did it suck so much at re-learning? Now when idling it feels like it's going to die and almost every time I shift from a gear to neutral to slow down it will die and I have to start it while coasting before I can get on my way.

Is there something I can check before doing a throttle cable adjustment to fix this?


BTW: No check engine light and no other issues with the car before or after I took the battery off except for this. I made sure the engine was hot before reconnecting the battery. The only thing to note is the massive heat wave we've been having here lately. It was about 95 degrees out when I finished up the work on the car.
 

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How long did you let it idle after you reconnected everything? Did you have to fix any of the wires to the IAC or MAF?
 

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Idle is usually high during the re-learning process. You do not adjust the throttle to repair your problem. There is no throttle cable adjustment. The screw you see on the linkage is to stop the throttle plate. It is not an idle adjustment screw. You can increase the idle by adjusting on the screw to open the throttle plate, and then that will screw up the TPS, the IACV, and cause issues with an assortment of sensors because the ECU will think you have your foot on the accelerator all the time.

Disconnect the idle air control valve and see if that changes anything. If it does, you either need to clean the IAC, or replace it. In addition to this test, you can turn on the AC if equipped to see if the idle goes up. In the current condition, if the idle doesn't go up, the engine will die when the clutch kicks in.

Double check the battery terminals to be sure those are secure, and pull on the 2 small ground wires connected to the negative terminal by a stud. Those 2 are on ring terminals, and when you experience a lot of caustic buildup those rings can become damaged. The damage might not be visually evident with a casual glance so pull and tug at those to see if one breaks. It doesn't fit your problem description, but it's a good idea to double check those, and repair if needed after fixing extreme corrosion. To prevent future corrosion, I suggest coating both terminals with grease after connecting. Any grease will work. My negative terminal used to corrode excessively until I greased it. Now, no corrosion in years. I just used a can of wheel bearing grease that had been damaged.

I'm sorry if I was a bit rude about the throttle adjustment screw, but it's a pet peeve of mine. Since computer controlled cars in the 80's and any EFI- there has been no idle adjustment at the throttle body. I can't tell you how many times I've attempted to make repairs on cars where someone has been fiddling with the throttle plate stop screw thinking that it's 1950 and this is related to a carburetor. Lots of Japanese feedback carbs were ruined as well even though the service manuals warned that there is no air/fuel or idle adjustment needed. If you have one of those problems it's related to something else like a vacuum leak.
 

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I agree with Alex. Check the IACV. Another problem with the dtec is the PCV line behind the manifold...it is a PITA to get to but it does become brittle and crack, it will cause a vac leak and could be part of your problem.
 
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