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Pete, Technician
Category: Car
Satisfied Customers: 24171
Experience:  17 years automotive training and experience.
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I have a 2004 Optima, with about 124k miles, that since November

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I have a 2004 Optima, with about 124k miles, that since November I have had nothing but mechanical issues. It started with Check Engine light. Took it to reputable auto sales dealer, whose mechanics replace the Master Air Flow sensor. The next day, the
car ran horribly, so I took it back and they replaced the MAF and put a throttle control sensor. SInce then, the throttle control has been replaced three times. They suggested replacing the timing belt, which they did, still showed check engine light. They
took it to a Kia dealership, who claimed nothing showed up on their computers. I had a local auto parts store put it on a computer and it kept showing a problem with the O2 sensor, but the repair place put it on a machine that says the O2 sensor was right
on. Now, if I am at a stop and try to quick accellerate onto another road, the car almost stalls out and then decides to go. This is a dangerous thing, if I am trying to get on the road where traffic is coming. Doesn't happen all of the time, but it does get
your attention. What do you think?

My name is ***** ***** I am a Expert here at Just Answer. I noticed that your question was not getting a response and thought I would see if you still need help with this. If the auto parts facility had pulled a code out of the vehicles engine computer for an oxygen sensor fault and with what you have described here this sounds like this may be a fault with one of the oxygen sensors and most likely the one before the catalytic converter itself.I have seen this sensor fail before and cause this type of fault as it will read incorrectly and can cause a lean or rich running issue and can cause what you have described. It may be a good idea to have this sensor changed out to see if it corrects this issue.This may be an intermittent sensor failure and this may be why the dealer had seen it as working properly. I would also have the fuel pressure tested as a weak fuel pump can also be common and cause what you have described and can also set an oxygen sensor code for a lean running condition. Thanks Pete

Customer: replied 3 years ago.
Pete, how many O2 sensors does the Optima have? How come when the repair facility put the car on their machine, the readings were normal. Also, how is it that when there was a check engine light on, that the Kia dealership said there had been no codes nor did the light come on, yet right after I picked the car up after they were done with it, the light came back on. Also, why is the throttle control sensor failing so often? All of the problems I've listed has transpired over a seven month period, since last November. What about the main computer? Could this be needing to be replaced? I can't afford to buy another car, new or used, and I am tired of dumping money into this one as it isn't worth all that much in the Blue Book. There are other problems too. I bought this car and since I've bought it, I have to replace the low beam bulbs about every few months. I've never had a car where I've had to replace the bulbs that often, maybe once or twice. Also, I am now losing oil between oil changes, but there is no leaking nor smell of burning oil. I am guessing also there doesn't appear to be any leaking around the gasket, least not that the repair shop has mentioned. The car has been pretty good over the almost nine years I've had it, but it is getting frustrating now.
( how many O2 sensors does the Optima have?)
2 one before the catalytic converter and one after
(How come when the repair facility put the car on their machine, the readings were normal.)
Their machine may have showed at the time that the engine is/was operating properly or they may have accidentally erased the fault codes.
I would have returned to the dealer right away while the light was on so they could re check the codes with the vehicle still running
(why is the throttle control sensor failing so often)
This may have been a misdiagnosis on their part or there may be some wiring at fault causing this issue.The wiring to the sensor should be checked.This may also be an internal fault with the engine computer itself if the wiring checks out o.k.
The low beam issue may be with faulty bulb sockets as I have seen the socket terminals spread open slightly and cause poor contact which can cause a voltage surge and burn out the bulbs.Also make sure the correct bulbs are being used as the incorrect bulbs can cause this as well.
The oil loss may be burning oil past valve seals or the piston oil rings,this would need to be checked into further to locate which component is causing this.Every vehicle is allowed to use a small amount of oil in between oil changes but usually no more then a quart to a quart and a half.
It's unfortunate to hear of all of these troubles you have had with this vehicle here,in some cases future repairs may cost more then what the vehicle may be worth depending on the repairs that need done.
Thanks Pete
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