Car slows slightly then corrects every few seconds

J.T.70

MEMBER
2019 KIA OPTIMA
2.4L
4 CYL
2WD
AUTOMATIC
1,151 MILES

I've driven V8's for 50 years, this is my first 4 cylinder, GDI engine, first foreign car, first modern automatic transmission, and I'm not used to this car yet. I don't know if what I'm feeling is normal or not.

I don't like the way it feels like the transmission is shifting when I don't expect it or want it to, and not shifting when I expect it to.

First: The transmission's seemingly excessive shifting is making the car respond late to the accelerator. If I have to move fast and I give it gas the RPM's jump way up but the car doesn't really respond until the RPM's come down and the transmission shifts for a few seconds to get back into cruising range. The result is the car doesn't move nearly as quickly as I'd like. If I want to get out of someone's way fast, waiting several seconds because the transmission wants the engine to be at low RPM's and not accelerating hard takes way too long. I'm used to instant response from the old V8 FI engine I had for 30 years.

Second: This car feels like it's making multiple quick little slow-downs and corrections while cruising at 20-40 mph. It doesn't show on tachometer or speedometer but my body feels it. This happens while driving at a constant speed and also during mild acceleration from a stop. It feels like the trans is shifting much more than it needs to. Or possibly it's a problem in the engine, like fuel delivery?

Third: I accelerate to 30 mph for a stretch several blocks long and hold it for a while but it may suddenly slow down several mph so I give it more gas to go back to 30 then as I hold it there it keeps accelerating beyond 30, like it's taking more gas than I was giving it and I have to let up on gas. This does show on tachometer and speedometer.

It may be that I only notice these things at slower speeds because road bumps are fewer. I may not feel the speed changes for several minutes or it could happen several times in one minute. I notice it practically every time I drive on side streets.

There have been no error codes displayed or found by the dealer. They test drove it but I couldn't go with so I couldn't point out the subtle things I'm feeling or tell the tech if he was driving the right speed or not. The tech said it felt normal to him. I've had the car 6 months and I feel like I'm getting less accustomed to it rather than more as time passes.

3 Replies

94 TRANSAM

MECHANIC
680 POSTS

Okay, so here's the thing. First Kia's electronics are not the best. They have always responded very slow to input. Second, as for the transmission. Kia uses small motors with low horse power and then gears the transmission way down to compensate for the lack of power. As a result you do have a lot of shifts because the rpm range for each gear is so narrow. You are always very close to an up or down gear. Most of what I hear you say is normal for Kia.

As for the slowing down issue, I would suggest manually shifting it as you drive. When you choose a gear it will stay there as opposed to the computer doing so. So if you feel the issue between 20 and 40 manually shift it from first, second to third and leave it in 3rd and see if you feel the slow down. My guess is the slow down you feel is from the converter locking up which puts a big load on the motor that it doesn't have the power to handle at low speed so it slows down making you step on the gas more which will open the converter and make it feel like a shift.

Try that and see if you don't feel the slow down. But it all sounds like a Kia to me.

Let me know what you find out.

Rich