Misfiring

LISA CRAWFORD

MEMBER
2005 KIA OPTIMA
2.8L
20 MILES

At idle in drive or in neutral my car is misfiring. Getting worse. I am told I probably just need a time up. Is that true?

Thursday, January 9th, 2020 AT 7:32 PM

5 Replies

JACOBANDNICKOLAS

MECHANIC
109,747 POSTS

Hi,

There is a good chance it needs tuned, but many different things can cause a misfire. What I would recommend is to have the computer scanned to retrieve diagnostic trouble codes. That should help us determine if it is a tune up or something different that is causing the problem. Here is a quick video that shows how to scan a vehicle:

https://youtu.be/YV3TRZwer8k

I realize most people don't own a scanner. However, most parts stores will do it for free or lend / rent you a scanner. Truly, this is where I would start. If you decide to scan it, let me know the codes that are retrieved and I can direct you what to do.
Here is a link that you may find helpful:

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Also, please confirm if this is a 2.7L V6 or a 4 cylinder as well as the mileage on the vehicle.

Take care,
Joe

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Thursday, January 9th, 2020 AT 8:23 PM

LISA CRAWFORD

MEMBER
4 POSTS

Thank you for replying. I have used a code reader on my car and the code read PO325 Knock Sensor no.1 circuit malfunction (Bank 1 or single Sensor?). Also you asked me to add a couple of things about my car. It is a 4 cylinder - 2.4L with 184,000 miles.

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Friday, January 10th, 2020 AT 6:31 PM

JACOBANDNICKOLAS

MECHANIC
109,747 POSTS

Hi,

Okay. The sensor is located on the driver's side of the engine toward the bottom. See pic 1 for location. Simply disconnect the wire to it and unscrew it and replace it. When doing this, make sure the wiring on it is in good condition and not corroded or damaged.

Let me know if that takes care of the issue. By the way, there is only one bank on this vehicle. If it was a V6, it would have two.

As far as a tune up, if it has been a long time, it is a good idea to do it. If for no other reason, do it for preventative maintenance. Here is a link that explains how in general how it's done:

https://www.2carpros.com/articles/how-to-tune-up-a-car-engine

Please keep in mind that if the timing belt is due to be replaced, it can cause a rough running vehicle. Also, it has a lot of miles, there could even be a compression issue.

Let me know if this helps or if you have other questions.

Joe

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Friday, January 10th, 2020 AT 7:46 PM

LISA CRAWFORD

MEMBER
4 POSTS

I haven't changed the knock sensor yet. I decided to do a minor tune up first. The results are, it's no longer misfiring like it was, but now my battery, idiot light, is staying lit up? Never was on prior though. I checked the battery terminals and they both seem to b tight. Any suggestions?

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Saturday, January 11th, 2020 AT 9:12 PM

JACOBANDNICKOLAS

MECHANIC
109,747 POSTS

Hi,

First lets determine if there is a problem with the alternator. Did you disconnect any wiring when you did the tune up? Is the belt still tight? Also, lets see if the alternator is actually charging and you are getting a false positive indication. Here is a link that shows how to test the alternator. It's really easy and only requires a multi meter or volt meter.

https://www.2carpros.com/articles/how-to-check-a-car-alternator

Here is a link you may find helpful:

https://www.2carpros.com/articles/how-to-use-a-voltmeter

Let me know what you find.

Joe