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Discussion Starter · #1 ·
Replaced timing belt and reman. head. Runs fine till it warms up, then it idles lousy, surges from 1,000rpm down to 700 or 800rpm, sometimes after reving the engine it will rev to 2,000rpm by itself. Sometimes stalls. Acts irratic. Replaced the O2 sensor, injectors and fuel rail- same problem. Comes up with P0170 fuel trim code and also a code for rpm higher than expected. Any ideas without throwing more parts at it?
 

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I have a 02 rio and it does it. I found a TSB that says the computer needs to be reflashed. I dont know if it the same for yours or not but hope it helps. I would call the dealer and find out
!
 

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2008 SpectraSX, 2014 Optima LX,2006 Jeep Liberty, Linux Mint Mate
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Try cleaning the IAC (idle air control) valve located within the throttle body (aluminum "tube" that the large rubber hose is attached to)... Carbon build up on the throat (inner walls) and the butterfly valve (round metal disk in the "tube"). Use choke and carb spray cleaner and a soft cotton rag... An old toothbrush helps also but check to make sure the plastic is not attacked by the cleaner. Push the bottom of the butterfly in and clean the edges where it closes. This may solve your engine searching for idle speed and sticking at higher RPMs.
Dave
 

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Discussion Starter · #6 ·
Already cleaned the throttle body w/carb cleaner. I also took the IAC motor out and sprayed the 2 ports, can't tell if it's working though. Is there a diagnostic procedure for the IAC motor?
 

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I haven't had a chance to get it to the dealer yet. In the meantime I have been resetting the computer. Makes it go away for a few days than comes back.
 

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2005 Kia Rio
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With the IAC off of the TB you can connect ground to one terminal and 12v power to another to make sure that the IAC opens and closes. Be sure that you have a good connection to the terminals. I used aligator clips. Make sure that the valve inside opens and closes smootly and completely. I did the same test to a new IAC to make sure that they performed the same. I am having similar problems and I still havent found the problem. I have check the Mass Air Flow, TPS, installed new plugs and wires, cleaned the throttle body and replaced the Catalytic convertor. I am going to check the Oil Control Valve in a couple of days when I get home since this part effects the advancing and retard of the cams.
 

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Discussion Starter · #9 · (Edited)
Fixed the fuel trim P0170 error today. It was a bad IAC motor. The IAC has 3 pins on its connector. The middle pin is 12V and the 2 outside pins are gound. Connected 12V to the middle pin on the connector and touched ground to one of the outside pins to see if the blade moves. Mine did not move just made a click. Replaced IAC motor, reset code, runs and idles normally.
 
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