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Discussion Starter · #1 ·
Hello, please bear with me, I have a lot to type out and describe.

We bought a 2014 kia forte koup 1 year ago, it had 107,000 miles on it and it now has 140,000. A couple months ago it took a nosedive on gas mileage (MPG used to be 29 to 34, now I can not get it above 25 no matter what.) and it has developed a noise I can NOT track down. It is making a high pitched really fast buzz, or squeal/screeching noise that seems centered at the back of the engine middle area. (at least it sounds like its there from inside the cab) The noise comes and goes at various rpm's, usually starting at 3000 but sometimes as low as 2500 up to 3200 to start. As soon as I let my foot off the gas, and the rpm's drop back down under 3000, the noise stops. The automatic transmission does NOT slip, so I doubt that is it (plus the varying rpm's mentioned adds to that belief), and it is not isolated to simply being in gear as it occasionally makes the sound while in park too when I rev the engine. The sound is like the serp belt needing tightened, or like an idler pulley or a/c bearing is going bad. This engine has no idler pulleys, tensioner pulley or power steering pump, so I went ahead and replaced the a/c bearing to eliminate that possibility as well as the serp belt. (I have a rebuild kit for the alternator but have not done that yet as alternator bearings usually make a lower pitched howling or growling noise when they go bad and this is NOT like that.) My son was riding in the car with the passenger window down, and he swore the noise was coming from the passengers side of the engine while to me it sounds like it is on the drivers side. That is why I went ahead and changed belt and bearing to eliminate those as a possibility. The only other part I could see that may be making a possible "fast buzz or screech noise" was the exhaust vvt solenoid, so I went ahead and installed a new one of those as well. None of what I have done has slowed or affected the noise at all.

Now, for the fun parts, I am sure the engine has a valve stem seal slow leak because I do have to add oil regularly, I run 5w30 and have to add a quart or two per week usually. I believe the catalytic converter is stopping up (poisoned from the oil consumption) because going up hills has now become extremely difficult. The speed on these same hills was 65 to 70 easily, now it is slowing down to 50 to 55 and it does not matter if I have the gas pedal floored or not, I can floor it and it will NOT go any faster at all. I took the car to a machinist friend this morning to ask him if he has heard of this noise problem, he grabbed his stethoscope and said the high pressure fuel pump is really noisy, rattling like an engine that needs the valves adjusted. he said the exhaust cam sounded a little noisy, but intake cam area sounded fine. The only noticeable sound he found was from that pump. I know the usual vvt rattle engine noise a gdi makes, this is definitely NOT that noise. I do have a hand held temperature gun to check the catalytic area but have not had time yet to check that and make note for bad catalytic, but I intend to by this weekend.

Those are all the basic descriptions of its current troubles, now for my questions:
1 with it sounding centered at top back of engine, would there be any way the gdi high pressure pump could be making the noise I described? (I can not find anyone on the internet claiming they heard noise from it to know how they described it, and I know thats an EXPENSIVE part!)

2 is there a possibility that the converter could be causing backpressure and it is messing with the exhaust vvt solenoid or system enough to make the sound?

I do not know how to record the sound while driving to pinpoint where it is coming from or I would do that. I am really shooting blind here as there are NO codes to go by. I have read many people having stopped up catalytic converters that never threw a code, and it caused wierd problems so I thought I would ask here and see if anyone may give me an idea of anything else to check, or test. Thank you for reading, pondering it and hopefully helping.
 

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Sounds like your converter is clogged and likely causing your lack of power and possibly the noise. However, the oil consumption is a big issue and I wouldn’t put a new cat in it until you can start to figure out what’s going on. How often do you change the oil? Do you have any receipts from the previous owner of oil changes? That noise could also be a main bearing squeal from low oil pressure or a spin bearing, at which point your engine would be pretty much toast.
I’d figure out that oil consumption issue before you even think about figuring out noises. That’s crazy excessive and should have been a sign that something is seriously wrong with your engine.
 
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Discussion Starter · #3 ·
Sounds like your converter is clogged and likely causing your lack of power and possibly the noise. However, the oil consumption is a big issue and I wouldn’t put a new cat in it until you can start to figure out what’s going on. How often do you change the oil? Do you have any receipts from the previous owner of oil changes? That noise could also be a main bearing squeal from low oil pressure or a spin bearing, at which point your engine would be pretty much toast.
I’d figure out that oil consumption issue before you even think about figuring out noises. That’s crazy excessive and should have been a sign that something is seriously wrong with your engine.
Thank you for replying, the oil gets changed by me usually at or around 3000 miles. Yes I do realize it is excessive consumption. The squeal or noise is definitely coming from the top of the engine, middle area at the back side or exhaust cam side. As for receipts? no I do not have any of those, but the car has NO external oil leaks whatsoever, and it is not blowing blue, so it must be the valve stem oil seals. I have rounded up the tools needed, and parts needed, and intend on pulling everything down far enough to replace the seals 2 weekends from now, so I will know much more then. I am rather worried about the noise currently, and yes, I definitely know not to put the new cat on it until the seals are replaced. Once I get the cams removed to replace the seals, it will be pretty obvious if it is a cam "bearing" issue in the cradle.
 

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Thank you for replying, the oil gets changed by me usually at or around 3000 miles. Yes I do realize it is excessive consumption. The squeal or noise is definitely coming from the top of the engine, middle area at the back side or exhaust cam side. As for receipts? no I do not have any of those, but the car has NO external oil leaks whatsoever, and it is not blowing blue, so it must be the valve stem oil seals. I have rounded up the tools needed, and parts needed, and intend on pulling everything down far enough to replace the seals 2 weekends from now, so I will know much more then. I am rather worried about the noise currently, and yes, I definitely know not to put the new cat on it until the seals are replaced. Once I get the cams removed to replace the seals, it will be pretty obvious if it is a cam "bearing" issue in the cradle.
It doesn’t have to smoke to be piston rings, but replacing the valve stem seals is where I’d start. Just make sure you have the tools and knowledge to re-time the cams when you put it back together. You can also see how everything looks inside once the valve cover comes off, which is nice to know
 
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All that oil consumption ruined your converter. Could be time to cut your losses and move-on to something else. On your next high miles used vehicle purchase, examine the outer end of the tailpipe.

Don't buy vehicles with wet black soot on the outer edge.
Used, higher mileage four cylinder Hyunkia' vehicles (especially with turbos) exhibit the wettened stuff.

My motto is to buy Hyunkias new - but never buy the pre-2021's TGDI / GDI's used. When oil consumption starts, that's when it's time to sell-sell-sell. Never procrastinate - never wait too long, to get rid of it ASAP.
 

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Discussion Starter · #8 ·
All that oil consumption ruined your converter. Could be time to cut your losses and move-on to something else. On your next high miles used vehicle purchase, examine the outer end of the tailpipe.

Don't buy vehicles with wet black soot on the outer edge.
Used, higher mileage four cylinder Hyunkia' vehicles (especially with turbos) exhibit the wettened stuff.

My motto is to buy Hyunkias new - but never buy the pre-2021's TGDI / GDI's used. When oil consumption starts, that's when it's time to sell-sell-sell. Never procrastinate - never wait too long, to get rid of it ASAP.
Thank you for your input, I do know oil destroys a catalytic. This is why I have a new converter, and valve stem seals ready to go in it. However, when we bought it, it had 107,000 miles on it. There was no oily residue or black soot in the exhaust pipe that could be seen although I suppose the dealer could have cleaned that. The engine was not using any oil noticeably until 115,000 which was about 4 months after we bought it and I had done an oil change. Even when I last drove it, it was not giving any visible exhaust signs of oil being burned. No blue smoke, no white (which is usually more connected with coolant issues, but still, no visible signals other than oil being used but ZERO leaks. Considering most cars these days usually go upwards of 300,000 miles easily enough with proper care, I did not consider it to be high mileage, but about 1/3 through its life. At the time that we bought it, it was one of the only newer affordable enough vehicles in our area, and our daily driver had just broken down, so we did not have a lot of choices. We did research into it, and at the time found most reports being positive, most everyone saying they were quite reliable. Reports on older models had varying reviews. Shrugs, a person can get a lemon anywhere though. This is the first GDI engine I have dealt with, and honestly will most likely be the last. Have a good day!
 
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