Welcome and I am happy to share this problem with you. I have a Hyundai Teracan, 6-cylinder engine, 3500 petrol, 2006 model, 220,000 km. I disassembled half of the engine to change the engine gasket. After the maintenance was completed, I encountered a problem, which is that when I press the gas pedal suddenly, the RPM drops backwards and there is a kind of squiggle in the engine, then the RPM rises when I press the gas pedal hard. What is noticeable and constant is that when the gas pedal is pressed slowly, the car accelerates normally and there is no drop in the RPM, but the RPM indicator drops when I press the gas pedal hard. It does not respond when I press the gas pedal quickly, but the response is delayed, unlike if the gas pedal is pressed slowly. What is the problem? Thank you.
Does the RPMs rise normally if you press the gas pedal all the way to the floor and go into wide open throttle?
@oskool
Yes, of course, if the gas pedal is pressed all the way, the engine and the RPM indicator rise and respond, but the transmission, instead of giving us a smooth shift between fifth, then fourth, then third gear if the gas pedal is pressed continuously, because the original and correct thing is that when the gas pedal is pressed forcefully, the transmission transfers the motion from one gear to another, i.e. to the next gear smoothly and flexibly, but when I press the gas pedal forcefully, the engine sound rises and the transmission shifts from fifth to second or third, for example, or sometimes it may be directly to first, because the engine does not respond when the gas pedal is first pressed directly, since the engine does not respond to the gas pedal until it is pressed all the way, and in this case the engine sound rises and there is a malfunction in the motion transfer process in the transmission engine, so the motion is not transferred regularly and steadily. My sincere greetings for your kind interaction.
@oskool
Greetings again to you, I am sorry, does the gas pedal sensor that is installed in the engine gate that is connected to the gas pedal, pressure and decrease, play a role in this problem? I think it is disconnected or installed incorrectly, which means that the car or engine does not respond to the gas pedal from the first moment. What do you think about this doubt or possibility?
@fyahm2222367 When the gas pedal is pressed all the way to the floor, the engine computer goes into 'open loop' and uses pre-programmed air/fuel mixtures. When the gas pedal is pressed normally the engine computer uses 'closes loop' air/fuel mixtures based on the MAF, MAP, IAT, and O2 sensors. Was the intake manifold removed while changing the engine gasket? Which engine gasket was replaced? If the intake manifold was removed there might be a vacuum leak on the intake manifold somewhere. Causing too much unmetered air to bypass the MAF sensor. Check the short term and long term trim numbers using a scan tool. Positive trim number means the engine is running lean and might have a vacuum leak.
@oskool
Excuse me, what do you mean by intake manifold? Do you mean the refrigerator or the air intake gate?
@oskool I thought pedal to the floor was "clear flood" mode.
@oskool
Thank you for your interaction with me. Best regards.
There are some terms that you mean, and the machine translator, which is from Google, does not translate some words accurately, so I find it difficult to understand some terms, but speaking and writing in classical Arabic and not in colloquial Arabic makes it easier to understand exactly what you mean, and thank you for your skill in any case.
@Imperator Clear flood mode turns off the fuel injectors when starting the engine. Once the engine starts, pedal to the floor becomes wide open throttle (WOT) mode and kicks the engine computer into open loop fuel control. Here's a video showing WOT causing open loop on a scan tool. https://youtu.be/ENyDDEgm6Kc?t=197
@fyahm2222367 You said half the engine was disassembled to change a gasket. Which gasket was replaced on the engine?
@Imperator Correction. When in open loop the engine computer doesn't read narrowband O2 sensors, but continues to read MAF, MAP, IAT, and ECT sensors. I don't believe wideband O2 AFR sensors enter open loop during wide open throttle like narrowband O2 sensors do.
@oskool yeah I misunderstood what was going on. Anyway it's usually a fuel delivery problem.