*UPDATE 1/22/10 53k miles*
The check engine light still comes on and goes off very randomly. The car has days where it seriously lacks power. It's very noticeable to me. Other days it feels strong, like it normally does.
More recently, I've noticed when I come to a stop, the RPMs drop to about 500 RPM, below normal idle speed, and the car kinda vibrates and then catches its breath, brings the RPMs to normal idle of about 750 or so. I've brought the car in for this problem FOUR times now. Kia told me there are step-by-step measures they have to take to diagnose and fix the issue.
First, they required me to pay for an oil change, stating I had an aftermarket oil filter on (Havoline) and the oil flow rate is different than Kia's own filter. Seemed kinda bogus.
The second time, they just plugged the car up to their computer and verified the engine code being read.
The third and fourth times, they did the same thing.
The oil flow control valve was inspected. They said nothing is wrong with it. I still LOVE this car because it fits my lifestyle perfectly, but this single problem has become quite a headache. I've only got about 7k miles left on warranty. I'm afraid the engine is going to self-destruct or something major in general go wrong just out of warranty, which I cannot afford.
Kia has pretty much given up on trying to figure the problem out, which has left me feeling rather helpless. If Kia can't figure out a problem with one of their own cars, I doubt an independent mechanic can.
Don't give up yet! If that ONE problem is irritating you and keeping you from fully enjoying the rest of the car, my suggestion is to take it to an independent mechanic, preferrably an auto electrical specialist.
Very often, dealership mechanics will only be working on cars that are within warranty, and don't encounter the odd problems that happen years down the line, this is where independent mechanics have the advantage. Although yours is still under warranty, clearly if they couldn't figure it out it's because they haven't encountered it before and had the experience of knowing how to pin it down.
This is the age of computers -- even Corollas can have seemingly undiagnosable problems, where the mechanic needs to think outside the square rather than simply rely on the diagnostics computer reading, because the reading can be influenced by other symptoms.
Here in NZ, there are many auto electrical specialists used by dealers themselves where necessary. Give it a go -- and also try Googling to see if there are any Kia forums you could post it on.
I agree 100% with the last commenter. You should think that the mechanics at the Kia dealer should know about Kia cars, but they usually don't. And this is not a specific problem for Kia dealers, it's the same all over. They've simply hired a lot of grease monkeys that does routine maintenance and simpler tasks like exhaust and brake jobs.
Besides that, they have to rely on diagnostic equipment, and do 'black box' replacements actually not understanding why they are doing things. Usually there are one or two mechanics out of 10 that actually know what they are doing regarding car electronics. So it's better to take the car to an independent car electronics specialist that knows what he is doing, and that has an in depth understanding of the matter.
Car is currently at 56k miles. Still loving the car. Still running great.
Finally got Kia to fix the check engine light problem. After about 4 trips to the dealership, they finally figured out it was a faulty oil flow control valve, which I had previously suspected to be the problem. They replaced that and the check engine light has not come on in about a month now. Things look good!
I made the mistake of test driving the new Hyundai Sonata, as a possible replacement for my Optima. Loved the car. Hated my local Hyundai dealer. Very rude people to deal with. I walked out thinking how lucky I was to have my Optima still.
In that case wait until the new Kia Optima/Magentis models come out. Blogs have featured the new model, which I think looks better than the new Sonata.
But if the Sonata is a good car, then just go find another Hyundai dealer and give them your business. But seriously, wait for the new Optima to come out there.
Correct me if I'm wrong, but aren't the Kia Optima and Hyundai Sonata built on the same platform?
* UPDATE 8/20/10 *
My Optima is currently at 63k miles. Still running wonderfully. I have a lot of confidence in the car at this point. I'm sold on the quality to this point, even with its initial hiccups.
I don't believe I ever mentioned the "squeaky, creaky" noise turning out to be a component of the parking brake system. There is no fix. Kia basically told me it's just a characteristic of the car and there is no fix. It's something I've gotten used to. No biggie.
I also don't believe I ever mention a shaking in the steering wheel that the car has had from day one. I've had 4 new tires put on the car, yet the shaking is still apparent. The strangest aspect of this problem is that I can be cruising at a set speed, say 70mph, and the shaking in the steering wheel comes and goes over several minutes time. It'll be dead smooth, then a few minutes later starts shaking. You feel it in the steering wheel and the seat of your pants. Then a few minutes later, smooths out again. I don't get it.
I've read other people's complaints about this, but I guess there is no fix. It's not a huge deal, but a bit annoying.
I bought a Volvo, so now the Optima is up for sale.
I just bought a used 2006 Kia Optima with 59K miles on it, and as soon as it turned over to 60,000, the light came on. Now it went off, but did you know you are supposed to change the timing belt at 60K miles?