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Discussion Starter #1 (Edited)
I have a 99 kia sephia. The check engine code is showing miss on#3 cyclindar. It will hardly idle goes dead at red lights. I changed the coil pak, plug and plug wire. Reset the computer and the same problem remains. Check engine light came back on says same message. I filled the car up with gas yestereday and put in some fuel injector cleaner. Today I drove it a total of 55 miles and it had burned a half a tank. I am not sure what else to do at this point. You cannot pull off from a stop light with the AC on and have to manually shift because it is running so rough. Any ideas what to check next and how to confirm if it is the injector. someone told me to put a can of seafoam in it, but I want to make sure it will not do any damage to this year kia. Thanks for any help. I bought the kia from original owner in 2009 it had only 67000 miles. I have all maintenance records it was kept up according factory specs and all recall work was done on time. As of today it still only has 83000 miles on it.

Falethea
 

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'96 Camry v6 XLE, '00 Camry LE
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Greetings,

Welcome to the forum.

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From what you describe, (something) is commanding the ECM to dump large amounts of fuel into the motor when running,

Possible causes include:

Defective MAF sensor,

Illegal air (air entering between MAF -> Throttle body, vacuum leaks)

Illegal air (cracked Exhaust manifold / Exhaust system leak at primary O2 sensor)

Defective O2 sensor

Defective Coolant temp sensor and/or Air Intake sensor,

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Would recommend as a start hooking up a vacuum gauge and seeing if the motor is holding steady, strong vacuum at idle - if not, check all ports on Intake manifold / all hoses / look for leaks,

And would hook up an OBDII scanner to see what (sensor) values the ECM is seeing for

the MAF,
the Coolant Temp sensor,
the Air Intake sensor,
the primary O2 sensor..

the Short Term / Long Term Fuel trim values (STFT/LTFT)

the Ignition Timing at idle..

The issue could be mechanical (timing, valve-train) or fuel delivery (injector) related, but if you burned that much fuel in 55 miles, I suspect you have a sensor issue also..

* If you just changed (1) plug and wire, you should consider pulling and inspecting the other (3) plugs and changing as-a-set..

* Check the condition of the air filter, inspect and replace as needed:
* Consider using CRC-brand MAF Cleaner to spray / clean the MAF sensor

AFTER hooking up an OBDII scanner to check initial values, clean the MAF sensor, then rescan to see if cleaning helped lower the MAF reading to .4-.6 at idle..

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To summarize above, you need either do some basic tests yourself or have them done by someone with some basic diagnostic tools & equipment to check condition of the vehicle -- I wouldn't recommend replacing ($$$) parts based on someone's verbal diagnosis or recommendation -- including my list of possible causes for dumping that much fuel above,

Keep us posted on your progress,

GottaCruise
 

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Discussion Starter #3
Thank you i will check on those issues. I neglected to mention less than a year ago I replace the other coel pk and all the plugs and wires. I check them again and they were good. actually #3 was good but i replaced it anyway.
Falethea
 

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2015 Buick Verano "Leather Group", 2015 Kia Optima Hybrid
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What did you gap the plugs to?
 
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