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Weird Misfire Codes!!

5K views 21 replies 4 participants last post by  Rekan H 
#1 ·
Hi all,

I recently purchased a Kia Rio as a beater car. This one is literally as simple as they get. No AC from the factory and no power steering either and manual trans. Vehicle runs and drives amazing. No issues in that regards. Motor sounds good even on cold starts. Engine oil is brand new and correct weight. The issue I am having is the dreaded flashing check engine light. I can tell you exactly and how it happens.


I drove the vehicle for a couple days and cruised and drove perfectly attempting to have it just get ready for smog. Vehicle had a dead battery when I picked it up and the monitors were not set of course post the battery drain. All got reset very quickly within 15 minutes except the 02 sensor. After the couple days of normal driving and highway cruising at speeds above 65 miles per hour it was not, I decided it was time to just do the readiness monitor resetting per procedures. I did the the highway cruising thing and that's when the problem pops up. At exactly around 3k RPM's highway speed which is basically 56-60 mph's I will within 30 seconds get flashing CEL. Codes stored will be Cylinder 2 and cylinder 4 misfire detected. Keep in mind the vehicle did not hesitate or show any misfire symptoms but only give the warning. If i reproduce this enough times it will finally give a solid CEL and misfire will be detected. I put in new plugs. Cleaned the crap out of the throttle body as the pedal had a slight stickiness right in that pedal range and I assumed it was causing this. I also swapped coils between the sets and misfires did not move.Throttle body still felt sticky so I got a good used one and now no stickiness but same faults. At time it will also set cylinder 1 misfire detected also. I decided since the faults were showing up on the 02 sensor readiness procedure that maybe it just had a bad 02 sensor. I did the pre cat 02 and same issue is present. I can also replicate the fault on a lower gear and speed but it was around 25 MPH which was also another 02 readiness step per driving procedures. at around 55 miles per hour The vehicle will never set the codes but 02 sensor never gets ready. At any other speeds I get no misfires even at like 75 or 80mph. I am just stumped and I don't want to really throw a bunch of money into fixing this shitbox vehicle I purchased for the sole reason of it being reliable :(

Terrible sorry about the super long post but I like to give as much context as possible. I am considering replacing the post cat 02 sensor but money is starting to add up and I just cant justify it on this vehicle.

Best Regards,

Rekan
 
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#2 ·
Swap injectors around and see if the problems follow....
 
#3 ·
I might do that next and see. I just feel like if it were injectors wouldn't the issue happen under different loads also? Example being hard acceleration and low RPM high load. The car runs like butter even at 40 miles per hour low RPM fifth gear full throttle. Not an ounce of hesitation or stumbling from misfires. I've never actually felt a misfire on the vehicle. I've also been through about 3 tanks of gas in the process so I ruled out bad gas since it had been sitting a while. I will however swap injectors to find out. Thanks.
 
#5 ·
PS...the post O2 sensor only checks to see if the Cat is operating properly. It does NOT control anything. You can live without it. That is the job of the upstream O2 sensor. Don't know if you can afford the device Kiaguy recommends.... Good luck!
 
#6 ·
… Don't know if you can afford the device Kiaguy recommends....
Although I bought and have been using a standalone reader unt for a number of years, the most common option these days is to buy an inexpensive dongle and then download a cell phone app such as Torque for Android. It's a very inexpensive way for someone to acquire one of these useful diagnostic tools.
 
#7 ·
Really? Did not know you could do that, and I recently entered the modern world and purchased a smart phone!
 
#8 ·
Yeah I have had a blue driver scanner for over 7 years now and it works well and lets me see live data on many supported items including 02 data and fuel trims and other things. I'm glad I don't need to replace downstream 02 sensor. One less thing to worry about. I'm worried this vehicle has some time of timing issue or VVT Solenoid issue but oil is crystal clear and clean. Usually you see some dirty ass oil for those problems!! Uuuugh I am soo annoyed. I have had the worst luck with Kia's and Hyundai's. My 2015 Sorento has a timing issue now and bad differential. I've owned over 35 + BMW's and don't run into issues like this and they are easier to work on :( Believe me when I say it.
 
#12 ·
There are a lot of posts of crankshaft position sensor failures, which cause a number of symptoms including misfires. They are also known in a lot of cases to NOT throw a code when they're going bad. Also not knowing the maint. history of this car, the VVT oil control solenoid may be plugged up with sludge and causing VVT problems that MAY translate to misfires. Usually the Intake side solenoid is the "culprit" and easy to remove and check/clean.
Good Luck!
 
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#14 ·
That was going to be my next task today. Taking out the solenoids and cleaning. I have run into that on soo many other vehicles. Just poor oil change history and sludge on the inside of the mesh filters. I am going to do that regardless today and kinda move forward from there. I hope that resolved that issue. I will keep you guys posted and hope for the best here.
 
#17 ·
The other thing that jumps off the page about your situation is the multiple cylinder misfire (with flashing CEL), but no noticeable performance problems. I don't recall ever reading another report like that, and it's hard to understand how it can even happen, because in order to identify misfire, the ECM should be getting sensor input indicating that those cylinders are physically lagging behind the others which are firing correctly. Perhaps some additional live data with the engine under load will show something else that might shed some light on what's going on here.
 
#18 ·
Yeah it's just I get misfires on other cars and the car runs like shit you know. This one runs like a champion I mean in 5th gear its very easy to peg the gas pedal and go from 50 to 80 in a very reasonable pace and it will spin tires from a stop and rev to 6k with no problems and idles perfectly. I was working on my sisters Chevy Cruze yesterday replacing the turbo on it and didn't have time for the rio but today is the day. I am cleaning out the solenoids and I will drive it and try to record some live data and see.
 
#19 ·
Update still no information worth sharing from live data. I am going to call Kia as there was a TSB to address misfire codes randomly appearing a few years back and an update done to the ECM's to resolve it. I am really hoping this vehicle hasn't had one done. So that's my only next alternative. Wish me luck any other input would be nice. Even though the coils looked brand new I went ahead and installed another set and the problem didn't resolve itself.
 
#20 ·
Update again. The TSB is not covered and I would have to pay for them to just check to see if it was even performed. Kia dealerships near me all 3 of them are complete and incompetent morons, I am sorry but they cannot even tell me if the vehicle has any recalls and tell me they will call me back. I tried to just make an appointment for diagnoses and they said they would have a service advisor call me back. No one ever does.. Honestly I am never going to buy a Kia again in my life. Waste of money on every occasion I have done it bullshit issues with my Kia Sorento also. I am at a loss. I checked for vacuum leaks. Couldn't find any. Cleaned the MAF or whatever it is and that didn't resolve it. Vehicle has 4 new coils and 4 new spark plugs and issue is still persisting and replacement throttle body. I did a complete battery reset last night to drain the PCM and drove it again today and still nothing. I cleaned the VVT solenoids too and still no resolution. Oil is changed and clean as well. I worked as a service advisor for 8 years at BMW and we never had issues like this. My techs would find an issue and if it was tough we always had a way of solving it. I am telling you I've seen everything that could go wrong with any car and I've never had an issue as stupid as this Kia Rio. Any other information would be great if anyone has ideas. If not I am literally and I am not joking going to ditch it on the side of the road. I'm fed up. Car runs and drives great and you can take it to Vegas and back and Ive had it running for hour and hours without any mechanical issues. Sorry guys if I am being negative but I am just soo upset.
 
#21 ·
On re reading the thread here, and don't "sluff it off" as I've seen the whole "gambit" with a number of odd things on many cars in my career.
You did not post of pulling and checking the spark plugs. I'd suggest you do. I had a problem with our recently bough 3.5 motor Pontiac and found good electrodes ...BUT cracked main body porcelains on 2 adjoining cylinders. From what I've read here that the rio's call for plug change around 60k miles anyway and you did not post miles on the car.
This is also a timing belt motor, it's possible that it was replaced before you got it and was off a tooth on aligning marks. With VVT it's easy to have happen and VVT can to a degree "cover" up this, but can also show problems possibly like you post of. Also this would affect crank sensor readings at times of computer (cel) flashings. As I posted before about the crank sensor..many times will NOT set a code for it. Check timing belt pulley marks for proper alignment.
Last one is from your posting of some readings "spiking". I've heard of alternator output power spiking in the ECM and "upsetting" engine sensor readings. I suggest you check voltage output of the system looking for power spikes from the alternator. ...This last one is a bit of a "stretch" for a possible cause, but worth checking.
Just because it is a cheap, low end car does NOT mean the diagnostics don't have importance to keep things running correctly.....Good Luck! ;)
 
#22 ·
Thanks man I pulled the original plugs in it and they looked fine but I still replaced with a new set. The ones in it are new now. Coils looked new also like literally no dirt on them but I figured just in case I replaced them also. Mileage is 129k sorry if I forgot that one. I'll have to check tooth alignment for timing belt and see to make sure someone didn't F it up. Issue literally in my opinion only happens as the PCM is monitoring 02 sensor values. Literally as I am letting off the throttle in the IM testing procedure it happens. I'll keep at it I guess. It's just im not a mechanic but find myself fixing every damn car I own and the projects never end :/
 
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