Question about 2008 Kia Rio

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#1 cyl. misfire under load

Changed plugs and wires, #1 injector, ECU . With a stethoscope, I can hear the #1 injector stop clicking when the engine is loaded. Verified with noid light. This is on a 2005 KIA Rio with 1.6L engine, auto, AC. Idles OK, and drives fine until loaded ( taking off from a stop, or accelerating).

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  • wrench38 May 10, 2009

    Thank you for your response. I have not watched for movement, but have removed the harness wrap to check for chafing or other damage, and wiggle tested with the engine running in gear with brake applied. The problem remained constant.

  • wrench38 May 11, 2009

    It will be a few days before I can get back to the car and test further. Will I be able to see the injector pulse on an analog scope?

  • dustang25 May 11, 2010

    dumb question. have you watched the wiring harness under a load to see if it is maybe shorting out while the engine moves?



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The best thing i can think to do in you case is find out if you are loosing the 12v (unlikely) or the ground (more likely) one side of the injector will have a constant 12v. if the 12v is dissapearing under the load then just snip the wire and tie into one of the other injector feeds. they should all share the same fuse anyhow. if it is the groung pulse dissapearing just snip the wire by the injector and the computer and run a new one. shure it might look funny outside the loom but it eliminates all other possibilities. if the problem persists then you are looking at a connector fault or computer.seeing that you have replaced everything else this should get you back on the road. feel free to write back if you have any questions.. dustang

Posted on May 10, 2009

  • dustang25 May 11, 2009

    i would think an analog scope should be fine to use. i use a digital scope almost daily and that is all i have ever used. if you can set it as low as 20ms you should be able to see a good wave form including the signatue inductive spike, letting you know that the pintle in the injector is actually moving. the main thing i would want to see is if the 12v or ground pulse is leaving. i am sure that when the injector quits you will see nothing happening between the two injector wires( 0 voltage drop due to no current, open loop), that would explain the noid light quitting. but if you check between a known good ground and the injector feed wire you should hav 12v the whole time even if the ground pulse is missing, if not then there's your problem. if the 12v never leaves then you can bet the ground is. you can check for the ground pulse at the computer itself by connecting on lead to known good 12v, such as fuse, and the other to the injector wire in question should have the same color wire. just get a paper clip or something skinny and conductive and push it in right next to the wire in the connector. if you loose pulse there the computer is at fault if not then the wire is at fault. with the problem comming and going i would say that an ohm meter will render itself useless. though you could actually use a regular high impedance meter. dc setting on the 12v side to ground, and ac setting on the ground pulse side to known 12v usually reads less than 12v ac more like 5v but if it goes 0 or close to then there's your problem. hope this helps. sorry i work during the day and don't get to check the computer till later in the day.if you have anymore questions i'm here for you.



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