When I touch the gas the rpm drops and rises

[GKD]

Whenever I press the gas pedal until it reaches 1000 rpm and then release it, the rpm fluctuates like this like its trying not to stall. Is this normal or what causes this?

Car: 2010 Fiesta 1.4 TDCI, 190k kilometers.

https://youtube.com/shorts/aa-8yOXJXuU?si=7sF0naXPP-LRMnpn

Note: I only touched the gas 1 time and as you can see, it revved up 2 times.

Plus, sometimes when I turn the ignition, it takes 1-2 seconds for the engine to start.

 

[Handy Andy]

It may need to have the throttle body cleaned or inspected - there is a gasket on the bottom side of the throttle body to keep out dirt and debris. You own a 2010 - so there may be a sensor on the air cleaner box side of the snorkel that might need to be cleaned with some non-contact chlorinated - sensor safe throttle cleaner.

Did you have the airbox - air filter serviced? IF you've left this to a mechanic before - you might need to have them inspect the PCV breather tube and the air filter in that airbox make sure the PCV sponge and the air filter media is seated and clean - not saturated with oil.

IF you can - take off the snorkel and inspect the bore on the body - keep the engine off - your keys in your had - and you can move the plate on a regular throttle body in normal good condition - with finger pressure - you should try to see if the plate can move with finger pressure.

Look on the plate - it slopes to one side the lower side is the side that opens to the intake area - that is where you can push with your fingers to see if the plate moves - rotates on the shaft.

• Press it move it inward and let the internal spring retract back to closed position - it should work smoothly
• - if it can't do this or "jumps" or feel erratic like it's "loose" or binding - this may be the reason for the RPM jump. It can be a sleeve bearing is worn and or and the media used to chase the throttle body's plate position - might be wearing out
• - it's a lot of miles on the unit so it may need to be replaced.

Hope these ideas help you find a method that helps you get this fixed.

It can also mean you have cracked or loose hoses - but RPM seeking usually means the Throttle body or it's body-to-intake manifold seal needs some TLC.

 

[GKD]

It may need to have the throttle body cleaned or inspected - there is a gasket on the bottom side of the throttle body to keep out dirt and debris. You own a 2010 - so there may be a sensor on the air cleaner box side of the snorkel that might need to be cleaned with some non-contact chlorinated - sensor safe throttle cleaner.

Did you have the airbox - air filter serviced? IF you've left this to a mechanic before - you might need to have them inspect the PCV breather tube and the air filter in that airbox make sure the PCV sponge and the air filter media is seated and clean - not saturated with oil.

IF you can - take off the snorkel and inspect the bore on the body - keep the engine off - your keys in your had - and you can move the plate on a regular throttle body in normal good condition - with finger pressure - you should try to see if the plate can move with finger pressure.

Look on the plate - it slopes to one side the lower side is the side that opens to the intake area - that is where you can push with your fingers to see if the plate moves - rotates on the shaft.

• Press it move it inward and let the internal spring retract back to closed position - it should work smoothly
• - if it can't do this or "jumps" or feel erratic like it's "loose" or binding - this may be the reason for the RPM jump. It can be a sleeve bearing is worn and or and the media used to chase the throttle body's plate position - might be wearing out
• - it's a lot of miles on the unit so it may need to be replaced.

Hope these ideas help you find a method that helps you get this fixed.

It can also mean you have cracked or loose hoses - but RPM seeking usually means the Throttle body or it's body-to-intake manifold seal needs some TLC.

Thank you so much for your detailed explanation. I will check it all when I go back to city I live 🙏

 

[Handy Andy]

I have more news...



Re-looked and re-reviewed your short - caught something that might help.

This "double" rev-up is from the system "adjusting" the mixture and the jump is from the system thinking that as you raise the RPM up then back off, the "double take" it does; is from itself seeing a higher than normal emission output in the tailpipe so it tries to figure out this condition.

The system is working properly, but there are signs of wear - the extra bump is from this - so it usually means a tune up of some form or another is needed even up to some form of a replacement - either by Throttle body - or the accelerator pedal - in the process of using these two; one tries to follow the other - only the PCM is moving the plate of the throttle - not you - so the system does this double bump as a sign it can't track the pedal quickly enough to let the throttle plate respond - or - the throttle plate, spark plugs, air filter or hoses associated with the intake - are not allowing enough advance, burn or air to pass thru so the system leans out the mixture by the double bump as a means to clear out the excessive emissions it thinks it's generating.

• A properly running (Fiesta) motor would allow the RPM to idle down slowly - so this might be the wear I was talking about earlier - the dirty throttle plate backs down and gets trapped too close to being fully shut so it (the PCM) pulls the plate back up as this double bump.

Think of it this way, in older carburetor days, in order to make the engine rev and gain power to accelerate extra fuel was sent thru the throttle bore plate using an accelerator pump as you moved the throttle plate thru your pedal. Done as a method to provide more power to accelerate - a means to add more fuel to make the system take on more power as you opened the throttle letting in more air.

When you close it off too soon, the system sees itself as runs too rich and can foul out the spark plugs from the extra fuel in the system pulled in by higher vacuum and the un-burnt fuel just adds more stink to the exhaust formed. So it may "die" (stall or chug) by lowering the idle speed by the extra vacuum formed from that rapid close of the plate, causing it to stall in a flooded condition. To try and fix that they used different methods and to help with that, engineers formed an Idle-up process to help reduce emissions by leaning out the idle mixture by opening the throttle just enough to cause a lean condition in the idle circuit before the ports for more fuel opened - this was a tricky method and caused several stall-type of conditions that most people during the day - wished for fuel injection; for carbureted engines were prone to uncontrolled fuel spillage into the intake causing to have the engine flood out and stall due to the lugging and drop in RPM caused by not enough air getting past the plate and leaning out the mixture - drying it out, so it can still run.

• Instead, it fouled out the plugs with fuel and stalled the motor and to recover quickly, you have to crank the engine with your foot on the throttle - just enough pressure - to open the plate and get enough air in there to dry out the plugs so they could fire again. But remember the accelerator pump pushes more fuel in every time you used, opened or pumped the pedal - ad infinitum...

I'd try to clean out the throttle body bore to see if the system can recover without having to do any really big rebuild or replacement without checking to see if the thing just needs a little TLC and cleaning.

 

[GKD]

I have more news...

View attachment 9590

Re-looked and re-reviewed your short - caught something that might help.

This "double" rev-up is from the system "adjusting" the mixture and the jump is from the system thinking that as you raise the RPM up then back off, the "double take" it does; is from itself seeing a higher than normal emission output in the tailpipe so it tries to figure out this condition.

The system is working properly, but there are signs of wear - the extra bump is from this - so it usually means a tune up of some form or another is needed even up to some form of a replacement - either by Throttle body - or the accelerator pedal - in the process of using these two; one tries to follow the other - only the PCM is moving the plate of the throttle - not you - so the system does this double bump as a sign it can't track the pedal quickly enough to let the throttle plate respond - or - the throttle plate, spark plugs, air filter or hoses associated with the intake - are not allowing enough advance, burn or air to pass thru so the system leans out the mixture by the double bump as a means to clear out the excessive emissions it thinks it's generating.

• A properly running (Fiesta) motor would allow the RPM to idle down slowly - so this might be the wear I was talking about earlier - the dirty throttle plate backs down and gets trapped too close to being fully shut so it (the PCM) pulls the plate back up as this double bump.

Think of it this way, in older carburetor days, in order to make the engine rev and gain power to accelerate extra fuel was sent thru the throttle bore plate using an accelerator pump as you moved the throttle plate thru your pedal. Done as a method to provide more power to accelerate - a means to add more fuel to make the system take on more power as you opened the throttle letting in more air.

When you close it off too soon, the system sees itself as runs too rich and can foul out the spark plugs from the extra fuel in the system pulled in by higher vacuum and the un-burnt fuel just adds more stink to the exhaust formed. So it may "die" (stall or chug) by lowering the idle speed by the extra vacuum formed from that rapid close of the plate, causing it to stall in a flooded condition. To try and fix that they used different methods and to help with that, engineers formed an Idle-up process to help reduce emissions by leaning out the idle mixture by opening the throttle just enough to cause a lean condition in the idle circuit before the ports for more fuel opened - this was a tricky method and caused several stall-type of conditions that most people during the day - wished for fuel injection; for carbureted engines were prone to uncontrolled fuel spillage into the intake causing to have the engine flood out and stall due to the lugging and drop in RPM caused by not enough air getting past the plate and leaning out the mixture - drying it out, so it can still run.

• Instead, it fouled out the plugs with fuel and stalled the motor and to recover quickly, you have to crank the engine with your foot on the throttle - just enough pressure - to open the plate and get enough air in there to dry out the plugs so they could fire again. But remember the accelerator pump pushes more fuel in every time you used, opened or pumped the pedal - ad infinitum...

I'd try to clean out the throttle body bore to see if the system can recover without having to do any really big rebuild or replacement without checking to see if the thing just needs a little TLC and cleaning.

Thank you for the explanation. I just bought the car, it's my first car, and I'm not very familiar with it yet. I also more or less understand what you're saying, but I'm not fully versed in the details. I didnt really get what you mean with "wear". You mean the throttle plate, right (or the engine?)? I mean, is it a sign of the bad engine or just about the throttle plate etc? What I'm curious about is, will it lead to significant costs for me, like an engine replacement? Or is it something that can be fixed with repairs such as a throttle plate replacement? I will try cleaning the throttle plate, but the car is not with me right now. Could this situation escalate to a complete engine repair? That's what I'm worried about.

It doesn't make this everytime, sometimes it makes and sometimes it doesn't. I start the car, press the gas and it doesnt make any fluctuation. Then I stop the engine, go home and next day it does it (only around 1k rpm, not much or less).

Plus, the car is running properly on the road and, not feeling bad or making weird noises etc. and its performance is good I guess. Would it be a problem to drive the car for a while in this condition? As I mentioned, I just bought the car, and as you can guess, I don’t have much money left

Sorry if I'm asking dumb questions, I'm just a little worried

 

[Handy Andy]

In the throttle body, the "shaft" the plate is bolted to - rotates using a set of gears driven electronically by a motor.

You Fiesta (mine too) - the vehicle - by this design, is considered a Drive By Wire - meaning your input to the pedal is not moving the plate by some form of physical connection thru a cable or gear, but by using an electric motor to move the throttle plate - the PCM or your vehicles "Brain" does this automatically and in a way that lets the system maintain proper control of power and the emissions so you get acceleration as you move the accelerator pedal and it responds in operation, so you get to drive - yet stay "clean" for the environment.

The signs of wear I'm referring to are the ways the system responds to how the motor takes to the input from your foot on the accelerator and tries to follow - it then monitors the output and adjusts the RPM in subtle ways to correct a condition it sees - so this may indicate wear on a fine-tuned portion of the system, be it; Throttle plate and dirt affecting how much air gets by - onto other more drastic conditions that can affect components that also can wear being the sensors on the Camshaft and Crankshaft as well as Exhaust catalyst, pistons, oil and coolant systems; these systems are also monitored by that Brain.

You will be fine to operate the car in this condition but if you encounter starting problems or driving issues where it doesn't drive like you once remembered it, then think back to this point in time and these posts to help you find a course of action.

 

[GKD]

In the throttle body, the "shaft" the plate is bolted to - rotates using a set of gears driven electronically by a motor.

You Fiesta (mine too) - the vehicle - by this design, is considered a Drive By Wire - meaning your input to the pedal is not moving the plate by some form of physical connection thru a cable or gear, but by using an electric motor to move the throttle plate - the PCM or your vehicles "Brain" does this automatically and in a way that lets the system maintain proper control of power and the emissions so you get acceleration as you move the accelerator pedal and it responds in operation, so you get to drive - yet stay "clean" for the environment.

The signs of wear I'm referring to are the ways the system responds to how the motor takes to the input from your foot on the accelerator and tries to follow - it then monitors the output and adjusts the RPM in subtle ways to correct a condition it sees - so this may indicate wear on a fine-tuned portion of the system, be it; Throttle plate and dirt affecting how much air gets by - onto other more drastic conditions that can affect components that also can wear being the sensors on the Camshaft and Crankshaft as well as Exhaust catalyst, pistons, oil and coolant systems; these systems are also monitored by that Brain.

You will be fine to operate the car in this condition but if you encounter starting problems or driving issues where it doesn't drive like you once remembered it, then think back to this point in time and these posts to help you find a course of action.

Thank you very much for your helps mate. I'd better show this to a good mechanic, then there won't be any question marks in my head. You helped me a lot, my friend. Thanks