2006 santa fe erratic idle and surges

I have a 2006 Santa Fe gls, 6cyl/4spd auto. I have 23000 miles on it. I've had oil changes done at the dealer since i purchased the car new. About every 2500 miles. On the last
visit, the mechanic recommended a transmission fluid change. I had it done last week, and the day after, the car started to idle erratically. It fluctuates between 700rpms and up to 1200 rpms. Also, when driving at any speed, and coming to a stop, the rpms drop to about 400, and the car feels like it wants to stall. At times when stopping, and the rpms drop, they don't come back up until I apply gas. Other times like when parking in the driveway, the rpms stay low, and when i put it into park, they jump to 1200. I went back to the dealer today, and the mechanic said he could not duplicate the problem, and there were no trouble codes. He also said that if there was a problem, the check engine light would come on. So i'm guessing that no codes means no problem? (sarcasm)? I don't know if it means anything or could be part of the cause of this problem, but after I had the tranny flush and oil change, when i got home, i noticed a few drips on the driveway. I slid under the car and the crossmember and plastic guard were covered in fluids and dripping. I took it back to the shop and they cleaned it up and said there were no leaks. I wondered if the slob mechanic might have gotten some connectors wet with oil or tranny fluid. If anyone has any ideas about the rpm problem i would love to hear them, maybe i can help the mechanic do his job better.
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Maybe you can find a better mechanic. Changing oil at 2500 miles is wasteful. Having the trans fluid changed at 23,000 miles does nothing but make more profit for the dealer.
The service may have nothing at all to do with the surging you are experiencing, but then again, it could. Perhaps during the sloppy work they did that left a mess under the car, a vacuum line or linkage was damaged. I'd find a new dealer, and I'd recommend you check the intervals suggested by Hyundai and save some money. Given the fact that you have 23,000 miles on an 06 model, you probably fall closer to the 7500 mile interval. Unless you are in Antarctica or drive 100% on dusty back trails.
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I cannot think of any reasonable relationship with the service work and your symptoms, even if the mechanic was messy.
The lack of a check engine lamp doesn't mean that no problem exists, just that the ECM hasn't detected one. Of course, if it's not occurring when the mechanic checks it, and there are no trouble codes to evidence the nature of the problem, proper diagnosis will be at the very least difficult, and in most cases impossible.
What engine do you have in your Santa Fe?
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It has the 2.7l six cylinder / 4sp transmission. It seems like the rpm fluctuation occurs when it down shifting from 2nd to 1st gear. I also checked the fluid level today when it was at operating temp, and it looks like it overfilled by about a quart. The owners manual says it requires 8.98qts and I looked at the work order from the transmission flush and they charged me for ten quarts. I don't think they used the fluid extractor, they just drained and filled. A previous poster said that a fluid flush was not necessary, and I agree. The manual says inspections up until 105000 miles, then fluid change. I only had it done, because when I had the previous service( oil change, tire rotat)etc. the mechanic recommended the flush, and it is on the work order, and shows that I declined the service at the time. Thanks for your help.
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My original thought was perhaps a stuck EGR valve or solenoid, but since the 2.7 engine doesn't have an EGR, that theory is blown out of the water.
Check the air intake bellows between the air flow sensor and the throttle body. It should be secure on the sensor and on the throttle body and have no leaks. Also check the PCV hose to be sure it's connected to the PCV valve and is not leaking.
In regard to the flush, if they used 10 quarts, they definitely did a flush. A drain and fill only removes about 5 quarts from the transmission.
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Ok, went back to my dealer today as scheduled. They had me there for about three hours, and the mechanic said he replaced the Idle Air Control valve/motor, because it had carbon on it. I took it home, and it still had the same symptoms. So, I called another dealer about an hour away, and luckily they had an opening this afternoon. I drove there and the car still did the same thing the whole trip. The mechanic had me drive it while he was in the car, so that he could itness what it was doing (the other guys didn't). He saw what the engine was doing, we went back to the shop, and he hooked up the computer to the connector, and we went for another drive. As I drove, he watched the different paramaters, and said OK I got it. We went back to the shop, he installed a new Throttle position sensor, cleared the computer, and we went back out for another drive. Runs great now ! And I have a great shop to take my car to for all services now. He also checked the transmission fluid and had to drain off two quarts. Yup, the other guys even messed up a simple transmission flush. I guess i'll have to argue with the original shop to get my money back for that mess. Now my worry is what kind of damage did they do to my transmission by filling it over by two quarts?
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There won't be any damage to the transmission. It's vented to prevent pressure buildup. The worst thing that would have occurred would have been fluid coming out the vent.
I agree about your opinion on the second shop. They were clearly interested in repairing your car correctly, whereas the first shop didn't appear to do any investigation as to the source of the problem.
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