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Discussion Starter · #1 ·
I've got a little over 30k miles on my 5 and overall, it's been great. I've commented about my stumbling problem on other threads, but my issue seems to be unique.

Since I bought the car new, when I accelerate onto the highway, especially going uphill and typically in 4th gear, the car will surge and stumble until I let off the gas. It doesn't always happen, but it happens enough to be annoying and a little worrying. The car will be completely warmed up and actually seems worse after a long highway drive.

Today, I decided to try full throttle acceleration while in second gear and the traction control off. I've never turned off the T/C, so was curious if it affected acceleration. Well, it accelerated normally in 2nd gear until around 4500 rpm when, like a light switch turned on, power dramatically increased and the car really took off. And when I mean like a light switch, it was instantly more powerful. I tried it again, but could not recreate it.

I haven't brought it to the dealer, since these issues are so sporadic. However, I've never felt like the car is really putting out 200 hp and after today's sudden power increase, I'm wondering if there is something wrong all the time and I just don't know it. MPG is fine, I even got 32 mpg yesterday with 200 miles of mostly highway driving.

With various discussion regarding BOV's, does this sound like a possible culprit? Right now, I'm planning to bring it to the dealer to take a look. They have been pretty good in the past, but with the difficulty in recreating the problem, I'm not that hopeful.
 

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Definitely worth spending the $7 on an obd dongle and running Torque to see what your boost levels look like in those scenarios. Does sound like it's not holding them. Maybe the BPV is torn.
 

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Do you need a paid version of Torque to get monitors or the Free one will do that as well?



BTW, I am having similar issues.

There are moments it pulls so strong I feel like tires will lose grip. Other times, and that happens most often, it just accelerates. When I had ScanGaugeII connected, I managed to see 18 PSI a few times (with excitement), but most of the time it would go to 14-16 PSI. 15 is the most common.

Now, when I mentioned it to the dealer - they said waste gate is the only adjustment as BOV will not be responsible. I would agree to extent saying BOV either leaks or does not, hence I would not get to 18 PSI without tight BOV.
 

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Oh dear - sounds like a few of you have come across the same loss of power problem I have been encountering (see my various posts over the last year or so). Walpol5, your description that you've never really felt the car is putting out 200bhp is so similar to my experience. Manually resetting the ECU seemed to help, which lead me to thinking the adaptive settings in the ECU automatically detune the car and then don't allow it to get back to being the little grunter that it can be when everything is performing correctly. Anyway, I've had enough of it and will be selling / trading my Koup as soon as I can - the two years since buying the car brand new is long enough to be putting up with a gutless 4 cylinder, not to mention the hassle of a blown engine in the meantime - ugh.

Good luck to everyone - I hope you find a resolution to your power problems.

Johno.
 

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From what has been found a lot has to do with the hotpipe and if you haven't ran catch cans or cleaned the tb and all the boost hoses to get rid of the oil. Also check your plugs. I have noticed that my plugs get slightly out of gap once in a while so I am always checking.

Also if your totally stock I think it is the ecu pulling back timing and adjusting for something. Mine did that when stock but it did get better.
 

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Another possibility.

"2. Fuel line. This one is simple. If you have a car that is cutting out on power from 4500 RPM and or above that, yet it comes back on power after you get out of the throttle and back into the throttle... get a fuel line replacement. Either at the dealer or with us. Do not add more parts to the car to make it faster, and do not assume that a tune will fix it, because it will not."
Addressing the miss information....
 

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Discussion Starter · #9 ·
Just to be clear with everyone, my car is completely stock and will stay that way. I use the car for work and drive it 30k miles per year. I've made a couple of minor cosmetic changes - painted calipers, whiter halogen lights for the fogs and high beams, but that's it. Fuel line or BOV could be the issue and I'm hoping the dealer will address it. It's hard to replicate, so I'm not very confident that the dealer will come up with a fix. I won't have time to bring it in for a couple of weeks, but I'll let you guys know what the result is after the visit.
 

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It's hard to replicate, so I'm not very confident that the dealer will come up with a fix.
Did you check oil level?
Mien was overfilled. I could not say yet if that changes anything,
 

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It definitely sounds like it could be a fuel line issue, The dealership will only replace it if yours is one of the "affected" vehicles, however, it has seemed that any and all vehicles have been experiencing this issue, not just the ones that they say so. Also the revised line that Hyundai/Kia came up with does nothing but temporarily fix the issue, as in many cases we have seen that exact same issue return even after the dealership has replaced the fuel line with the "new" "Upgraded" line. I would definitely look into the Torque app and monitoring everything, and doing logs while trying to replicate the issue, then you will have some sort of proof to show the dealership when they try to tell you that there is no issue. If you want to go with our fuel line, that could be an option as well. High Quality and will not kink/split like the factory one.
Tyson
 

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Discussion Starter · #12 ·
I just changed it myself a few weeks ago. It's right on the money. It took the usual 4 quarts.
 

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Discussion Starter · #13 ·
So, for the past couple of weeks I have experienced zero surging or stumbling. Is my car reading this forum? Maybe it's the warmer weather or summer gas, but I can't get the car to stumble at all now. I hope it's gone for good, but I doubt it.
 

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Sounds like what happened to mine . Right before I blew the motor
 

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Had you always gone to the same gas station before having your issues? I really don't think a bad batch of gas would give you the issues you had for as long as you had them.... Maybe an issue with the actual station you go to?

My car feels like crap when its cold... I always baby it when its warming up but I still get hesitation on acceleration, also get a vibration in the pedal - just doesn't feel like a nice car to drive.

When it does warm up it feels great, but cold - watch out.
 

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Funny how the engine always seems to run the best right before the OH SHIT moment lol
 
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I have a very similar issue. Had my car since January this year and started having problems early in the spring. Been driving it without any issues before that, car has 25000kilos on it.
I noticed that the car seemed to progressively get more and more sluggish, this happened over a couple weeks. I attributed that to the change in temperature but it seemed extreme, I felt like I literaly lost 30hp.
Then one day, I felt some kind of misfire / stumbling as I was driving over a small bridge. I was going WOT climbing it so the engine was obviously under heavy load. That same thing happened a week later, same bridge.
As of right now, whenever I put the car in any kind of high load situation, this happens. It almost feel like the engine is knocking or something is slipping.
When the knocking happens, the engine seems to be GAINING power, almost like it is being restrained under normal driving conditions.
Yesterday, I was on the highway trying to overtake someone going WOT and instead of the usual stumbling I have come to expect, the car put itself in limp mode. I thought I blew something, not a good feeling.

Things I did before the issue:
- Tried premium fuel for the first time (I don't believe it to be related but some people said if affected performance, just putting it out there)
- Went to the dealer to check my gas pedal (since I can't seem to be able to keep it steady around 900-1000rpms in 1st gear in traffic, it jerks like crazy...).
Off topic but all this to say that the dealer reset the ECU "just in case" and this is when my acceleration issues started.

Disconnecting the battery to reset the ECU seems to fix it for about 20 kilometers or so. I get nice linear accelerations that actually feel like 201hp.
As soon as the ECU starts to "re-learn" new values, the car gets sluggish ans the problem starts re-occurring. This is what makes me think it it probably an electronics problem, If it was mechanical the ECU reset would not help at all.
Went to the dealer this week and they told me the crank position sensor was the LIKELY culprit, I will keep you guys posted when the swap is done.
OP: meanwhile can you try resetting your ECU to see if your results correlate with mine?
 

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Reset of the ecu sets it back to stock but if a sensor is bad or setting from factory it will happen again . I never tried but I've heard 0 tunes address this issue . John you can talk to . Jay is hard to contact about it . It's basically smooths out and makes the car run as it should . Stage one picks up boost .the zero seems to improve the car but is not popular because no real power gain . You also never hear reviews about it cause face it who brags about a car making the same power lol. After I get mine fixed im going to literally test every part to spec and pay for that stupid temp license to access the Kia repair factory manual again
 

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- Went to the dealer to check my gas pedal (since I can't seem to be able to keep it steady around 900-1000rpms in 1st gear in traffic, it jerks like crazy...).
What did they do about it? I get same. Try to get steady 1000 rpm when stationary...


Now, for your case - sounds like mine minus knocking.
I am in process of troubleshooting it myself. I will be running some tests this week, then clean intake, then go to spark plugs. It seems it has more power on cold (shortly after reaching operating temperature) as opposed to after a longer drive.
Also, octane boost to see if fuel makes any difference.

What I learnt so far is that boost is not constant and it builds kind of slow I would say. But hey, I cannot get any good data of compression vs engine speed at WOT for out turbo. Hence, I am unable to say if this what I see is good or not.
 
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