Question2002 Hyundai Sonata 4 cylinder - I have two questions
1) When I momentarily remove my foot from the accelerator at about 22MPH (when the transmission is about to change from 2nd to 3rd gear), the transmission slips out of second gear and into neutral. When I resume to accelerate, the engine's RPM's increase, because it's in neutral, and eventually the transmission slams into 3rd gear. I can repeat the problem on command. This problem was present with the original transmission, and continues to be present with the Hyundai dealership's replacement transmission. I can prevent the above from happening if I am careful not to stop accelerating when in the 22 - 25 mph range. The transmission is still under the Hyundai 100,000 warranty. Can you explain what is causing the above problem?
2) I brought the car to the dealership for the above problem (after the new transmission was installed). When I dropped off the car, it was running smoothly and the Engine light was not lit. The dealership's diagnosis found a defective fuel injector, which they claimed was the cause for the transmission problem, and they wanted to replace all four injectors. When I picked up the car, the engine light was lit and the car was limping along (one injector did not work). I had the single ejector replaced by my own mechanic, and the transmission problem remained. Was it coincidence or could the dealership have accidentally damaged the fuel injector while performing their diagnosis?
Answer1. Without being able to examine the vehicle and perform some service work, I'll be unable to reach a definite conclusion as to what is causing the transmission shifting issue. There are, however, two plausible answers:
A: The servicing technician did not reset and relearn the adaptive values at the time of the transmission replacement. The transmission control module (TCM) adapts transmission fluid pressure changes to keep shifts smooth as the transmission components wear. If it was never properly reset after the transmission replacement, harsh and/or extended shifts may occur.
B: Technical service bulletin (TSB) 02-40-003 indicates a reprogram for the TCM is available to address a shift flare on the 2-3 shift. The term shift flare simply refers to an increase in rpm during the process of an upshift. The problem you have could be considered a severe version of a flare.
I'd want to address both above items before searching elsewhere for the cause.
2. It's doubtful the dealer damaged the injector during diagnosis. They'd have no reason to inspect the injector unless there was some sort of indication that there may be an injector issue in the first place. I'm not sure why they'd want to replace all four, though. Additionally, your description of the transmission problem seems quite clear. This would have nothing to do with that issue.
