Fabia III accelerates/maintains speed on its own after releasing the accelerator pedal

[Warrior193]

Possibly suggest checking the throttle body setting - you will need to get someone to get readings from the OBD data port.

[nta16]

1 hour ago, Nix2 said:

Well, now what is definitely happening is that the idle speed simply NEVER goes down to the factory setting (approx. 800 rpm) and they stay at the level of 1000-1200rpm, which is why the car "accelerates itself"... I wrote earlier that the idle speed drops to the factory value, but this is not the case (I was wrong in previous posts). The idle speed is too high and it always happens, regardless of the engine temperature (which heats up quickly).

Another idea - is this with higher electrical loads like air-con on, turning steering wheel, others, does your start/stop always work when it should or do you get messages or warning lights - have you checked the state of charge of your battery at the battery terminal posts a good few hours after last driving the car?

 

For checking the checking the throttle body setting you might find someone on the following list near you able to help you with this or a report, some for free or beer tokens others perhaps as part of a professional service so at some other charge. -Briskoda VCDS Owners Map (click me) 

 

[Ootohere]

@nta16  The OP @Nix2is in Poland. 

 

@Nix2

Your coolant shows an indication of heating up quick to an indicated 90*oC, the engine / engine oil is not at operating temperature that quick though.

 

Is the high RPM you see there always even after 10 km of driving, and no matter you much further you drive and totally at an efficient temp?

Edited 17 March by Rooted

[nta16]

36 minutes ago, Rooted said:

@nta16  The OP @Nix2is in Poland. 

Sorry missed that jumping from page 1 to 2 - there is a pin shown for Moscow though!  Unfortunately none showing in Poland.

[Nix2]

The revolutions are increased regardless of the engine temperature, additional load, lights, air conditioning, turning the steering wheel or with a greater electrical load, e.g. air conditioning on, turning the steering wheel and others. The Start/Stop system always works when it should, with no messages or warning lights appearing.

 

I also checked the battery charge - the battery terminals show approximately 12.3-12.4V a few hours after the last car ride, and immediately after starting the engine it is 14.4V (proper charging).

 

The engine (apart from idle speed) runs well, consumes little, has good dynamics and warms up quickly (after approx. 2.8 km of running at a temperature of approx. 13 degrees C, it already reads 90 degrees C). There are no errors either in the engine or in other modules.

 

I have a VCDS interface and I checked the "throttle body adaptation" twice - in this engine model, this procedure takes literally only 2 seconds and a message about the successful procedure is displayed. However, this does not change anything, the revolutions are still at 1000-1200 (they randomly drop to either 1000 or 1200 rpm) - I also noticed minor irregularities in these idle revolutions - e.g. when pressing/releasing the clutch.

Edited 17 March by Nix2

[Nix2]

@Rooted

Yes, regardless of the distance traveled, the idle speed is too high and the temperature on the display is always 90 degrees C.

Edited 17 March by Nix2

[xman]

I sometimes noticed a similar behaviour in our somewhat older petrol Skodas. In most cases, if I blipped the throttle and sharply released my foot, the idle speed fell to normal. Sometimes just putting my foot under the throttle pedal and gently lifting it also worked.

Conclusion: throttle pedal slightly sticky and not returning fully to the end stop.

 

On other occasions where this didn't work, this seemed to be associated with an elongated warm up phase. Remember the temperature dial is not an accurate indicator of coolant temperature, it is manipulated to show normal over quite a large range. As discussed elsewhere 

Edited 17 March by xman

[Nix2]

In the Fabia III, the pedal is "electronic" - there is no cable, so it should not "jam".

 

I can do a test drive with the driver and read/record individual measurement blocks on VCDS, such as "accelerator pedal deflection", "throttle opening", etc., but which parameters should I pay attention to?

 

It seems to me that these revolutions are forced by one of the temperature sensors... perhaps, for example, the intake air temperature sensor?

 

(and the outdoor temperature sensor readings seem ok)

 

 

 

 

 

 

 

[nta16]

The possibles are sensor(s} error/fault and/or part(s)s fault((s) and/or programing errors.  Any VWSkoda program updates on your model/VIN?

 

9 hours ago, Nix2 said:

It seems to me that these revolutions are forced by one of the temperature sensors... perhaps, for example, the intake air temperature sensor?

In that case does the VCDS do live recordings graphs of the temperature sensors, intake-air temperature seems a good one to look at along with perhaps coolant sensors, air pressure  Could be a single thing or perhaps combination that the computer programs are trying to correct for (or perhaps messing up).

 

Have a look at and note your oil temperature reading when your your "water" temperature gauge needle(?) just gets to 90 and again later look at and note your oil temperature reading as the "water" needle remains at 90. 

 

At over 100,00-miles you will want things like sensors and throttle body reasonably clean physically and electronically for the computer programs to be functioning well from the info given to them.

 

IIRC with my neighbour's DIY/semi-professional/professional scan tool there were 638(?) data points for the engine on my wife's 2015 Fabia 1.2 TSI.

 

Again I am out of ideas - and sorry for repeating stuff as I didn't read the old posts before.

 

[xman]

On 17/03/2024 at 15:12, Nix2 said:

In the Fabia III, the pedal is "electronic" - there is no cable, so it should not "jam".

 

Its still a lever operated throttle position sensor connected to the pedal. Mechanical lever that can stick, or what I tried to explain, does not fully return to its end stop. Particularly if there is lots of debris around it.

 

All the cars I referred to were "electronic" or fly by wire throttle pedals as has been the norm for decades.

Edited 21 March by xman

[Nix2]

Yes it's true.

Today I connected VCDS (the engine has the UDS protocol) and what surprised me was the voltage of terminal 30 was very very low, from 12.7 to 13.7V!

This is the main PLUS and should have the same voltage as at the battery poles (which I measured earlier and which is approximately 14.4V at idle?

Perhaps this is the reason for the higher idle speed - "undercharged: battery?"

 

This is what it looks like.

 

[nta16]

9 minutes ago, Nix2 said:

Perhaps this is the reason for the higher idle speed - "undercharged: battery?"

You dismissed this earlier and was happy with your battery readings (at battery terminals).

 

Try checking the reading for the battery (at the terminals with a multimeter) many hours after the car was last used, perhaps the next day from overnight parking, and see if they differ much from before.

 

Sexy scan tools are all very well but the boring basics still need to be done.  So many take a lot of convincing that just because the engine starts and lights seem bright enough that the car battery might still be in a low state of charge (and health) which can cause all sorts of unexpected issues even before the warning lights and messages show.  If the battery is used/abused/neglected for too long/ too many times then even using an appropriate battery charger maintainer may not be able to recover it or recover it sufficiently.

 

Also of course checking the battery terminals and terminal clamps are clean and secure and the main cables and earths are in good condition and connections clean, secure and protected - of course you may have already done this.

 

A battery in a lower state of charge often will not help with diagnostics of engine staring and other electrical issues and may well hinder progress whereas a battery fully charged and in reasonably good condition will not hinder diagnostics and progress.

 

Of course your problem may have nothing to do with the state of charge and health of your battery but as I put it may influence diagnosis.

 

A number of times I've been assured "the battery is good" and it wasn't or I check the terminal clamps (or battery holding clamps) and they are loose, had this the other week on a two-year-old car that had the battery replaced under warranty by the Dealership  (Ren No! Nissan) positive battery terminal clamp offset so plastic cover wouldn't shut down and negative battery terminal clamp was overtightened so the clamp had bit into the battery post and needed a bit of work to get the two items to part from each other with very little room to get any tools in to assist with this.  Dealerships really can make a mess of the simplest of jobs.

 

[Nix2]

Yes, The voltage measured with a multimeter (a good quality one, Fluke, and in the "LowZ" mode, i.e. with some load) directly on the battery terminals at any engine speed is about 14.4V, and according to the diagram from Skoda Rapid (I can't find the diagram for Fabia III but I think it's the same) the main bus "30" is connected directly to the battery positive.

 

On this bus, the ECU (via VCDS) measures and gives a voltage of 12.7-13.7 V... so something is wrong.

 

Tomorrow I check all battery and ground connections.

 

 

 

Edited 26 March by Nix2

[nta16]

Something I meant to put in last post but forgot, also check the alternator, if the battery isn't great then the alternator has to do more, and it has 100k+-miles of work, flip side of course if the alternator isn't great the battery has to do more and isn't getting the all the help from the alternator it should.

 

Battery is like tyres, very important to the car but often under considered and overlooked - this issue might not be with the battery but affecting it, or perhaps something different or as well as.

 

Good luck let us know how you get on.

 

[Nix2]

I did a second longer ride, the voltage of terminal 30 ranged from approximately 12.2V to 14.4V and it changed literally every second, randomly.

 

Then I checked and cleaned the battery terminals, the battery ground to the body, and the entire fuse box and fuses directly next to the battery. (I wanted to check the ground on the engine, but I don't see such a ground cable anywhere)

 

There is some result - but not entirely, now VCDS shows the voltage at idle and on the road in the range from approx. 13.5V to 14.4V (it changes randomly) Now there are no indications of 12.7V, the minimum is 13.5V, the same voltage as the VCDS indications is on the battery terminals.

 

However, the revs were still higher (VCDS indicates approx. 950 rpm on a warm engine). Are these unstable charging the right lead in this case?

 

Or maybe it is "suspicious" because it is 5 years old (i.e. from new) and the car has start/stop...

 

 

[Warrior193]

On 17/03/2024 at 15:12, Nix2 said:

In the Fabia III, the pedal is "electronic" - there is no cable, so it should not "jam".

 

I can do a test drive with the driver and read/record individual measurement blocks on VCDS, such as "accelerator pedal deflection", "throttle opening", etc., but which parameters should I pay attention to?

 

It seems to me that these revolutions are forced by one of the temperature sensors... perhaps, for example, the intake air temperature sensor?

 

(and the outdoor temperature sensor readings seem ok)

 

 

 

 

 

 

 

Even with a 'fly by wire' throttle, there will be an end stop on the pedal potentiometer - the throttle tap may help to eliminate this as the cause.

[nta16]

Much of car servicing and maintenance and even many repairs often boil down to clean and lubricate.  You have already found the benefit of cleaning (and perhaps securing and protecting the electric connections) even deleting error codes is a form of electronic cleaning so you may want to consider further cleaning, see later.  I don't think there is an engine earth cable but I could be wrong. 

 

Is 950 really that high for the revs, how accurate is the VCDS reading - I don't know but what you have to consider is you are dealing with computer programs and physical parts and components if you think they are always extremely well designed and made and always function perfectly I have some financial investments I would like to show.  (I am joking.)  VW has very complex intertwined computer programs (and over intrusive to me) that are designed to get the best out of all the systems on the car and particularly to get the very last tiny bit out of possible fuel consumption and reduce emissions (ignoring everything they have put on the car against this and they can't cheat as much as they did previously).  These computer systems sometimes have to do unexpected stuff to meet all of the various requirements of running the car in such a way.  Now they have one cylinder less to do this and they don't have the heritage of others with 3-cylinder engines (the 4-cylinder were rough enough in my personal opinion).

 

Also you have a "smart" alternator and a battery charging program along with loads of other computer programs making their demands so I am not too surprised the figures vary (but I don't know VCDS or ever used one, look to be a horrible presentation of a computer program to me, something from the previous century but I know those that use it like it).

 

Using something like the VCDS is useful and sexy but as already proven going with the basics like clean, secure and protected electric connections (and wires) must not be neglected - a couple of posters have mentioned things like the throttle body and pedal why not look at physically cleaning and lubricating the pedal and if required cleaning the throttle body then resetting them with the VCDS.

 

I forget, did you actually fully recharge the battery with an appropriate battery charger or just rely on driving the car for the alternator to do the work?

 

Personally not having a VCDS I would have started with a spray cleaner lubricator on the pedal, check battery clamps connections then using an appropriate battery charger maintainer following the instructions in the Owner's Manual  and charger instructions, got the battery fully charged and see how things went and further investigations as required - but that's me, I'm not that interested in working on cars particularly ours. 

 

Good luck, keep going and let us know how you get on, you already have some progress.

 

[nta16]

ETA.

Have you cleaned the diagnostic port on the car and VCDS lead plug connections?  As with the multimeters, you should always test any testing equipment before conducting tests to confirm they are working correctly.  Though I have no idea how you would do that with a VCDS machine, other than making sure you have the latest updates installed (but if they are anything like Microsh1t they can introduce more programming problems that it resolves).

 

[nta16]

ETA.

Have you cleaned the diagnostic port on the car and VCDS lead plug connections?  As with the multimeters, you should always test any testing equipment before conducting tests to confirm they are working correctly.  Though I have no idea how you would do that with a VCDS machine, other than making sure you have the latest updates installed (but if they are anything like Microsh1t they can introduce more programming problems that it resolves).

 

And are you saying 950 on a warm engine by 'water' temperature or oil temperature, what consumer electrics were running at the time, what other items from programs were operating at the time, what should the revs be?

 

 

[Nix2]

 

29 minutes ago, nta16 said:

Also you have a "smart" alternator and a battery charging program along with loads of other computer programs

Yes, that's right, each car has its own (sometimes intelligent and sometimes not) charging algorithm, but what can be said for sure: there cannot be a voltage of 12V on terminal "30", because this means NO charging (and if there is no charging, the voltage will quickly drop to below 12V), then the voltage of the battery itself... of course we are talking about a running engine.

 

I also cleaned the OBD socket as a preventive measure

 

As for the revolutions - in all conditions, at all engine temperatures, the idle revolutions stabilize and amount to approximately 950 rpm (and this is also what the tachometer on the dashboard shows)

Edited 29 March by Nix2

[nta16]

I have not got a wiring diagram to remind me what terminal 30 is and where but I have seen those that are into electrics give it importance, I am not clever with maths and things like electric (or anything much really) so my simple mind thinks, depending on the electrics running on the car (the gods that are the computers and their programs of course) plus I cannot think or know what else a 2019 car would have running electrically but if very low and engine not under load then the less the battery needs charging the better as it has plenty/sufficient - but of course that does not allow for for faults and errors.

 

You are obviously way ahead of me, cleaning the OBD (that name I could not think of at that time so put diagnostic, that is my poor memory) port before I thought of it only one example.

 

950 does sound to me high for a modern car but my wife's 2015 Fabia Mk3 4-cylinder 1.2 TSI engine has all sorts of noises from it at various times as the computers do their stuff (whether I want them to or not) and the idle revs can be high for a while some of it I think is explained by the following link but may not be directly or indirectly similar to your issue (stuff VW do not want customers to know, or cannot be bothered to tell them, or only discovered by customers or dealerships, who tell them ) so only follow the link if you want. - https://www.briskoda.net/forums/topic/504258-a-tsb-from-skoda-on-cold-start-behaviour-with-12-tsis-something-that-dealership-employees-should-be-able-to-explain-to-customers

 

 

[Nix2]

I tested the car for 2 weeks and measured various parameters via VCDS.

 

Yesterday I drove a similar Skoda Rapid (2018, 120,000 km, in perfect condition, no errors, drives quite ok and according to the owner everything is ok) and... I discovered that the car behaves EXACTLY like mine.

 

Conclusion - this is how it should be! This Rapid "pulls" at idle speed...

 

A separate issue is the imprecise tachometer readings on the dashboard. I noticed that there are random readings from about 1000rpm to about 1200rpm, and the VCDS scanner constantly shows about 945-955rpm.

 

I will come back to the issue that the car drives itself, without pressing the gas pedal - I think this is an algorithm that prevents the engine from stalling (throttling) and that is why the controller strives to maintain such (increased) revs. (this suggestion appeared earlier in this thread).

 

I think that if someone drives dynamically (i.e. uses little engine braking), he or she will not notice that the car wants to move without pressing the gas pedal. However, if someone drives "eco" and sometimes allows the revs to drop to the magic limit of about 1000 rpm, they will immediately notice this phenomenon...

 

Regards

 

 

 

 

 

 

 

[nta16]

39 minutes ago, Nix2 said:

A separate issue is the imprecise tachometer readings on the dashboard. I noticed that there are random readings from about 1000rpm to about 1200rpm, and the VCDS scanner constantly shows about 945-955rpm.

This needs a separate thread, I've no idea how accurate the VCDS would be with a 2019 car but that seems a large difference.

 

I've been driving a couple of different 2023 car, one a VW SEAT 1.0, 3-pcylinder, 110, and the other a Ren-No! Nissan and testing them out in Eco, normal/standard and sport and I think some issues may come from owners/drivers who are interested in fuel consumption not understanding the basics that in basic terms fuel consumption is about throttle pedal movement and revs and higher gears being gentler on engine wear and mixing the two up engine wear and consumption by running at too lower engine revs and gear.

 

I proved this to my neighbour who likes to look at the car's (claimed) on-board computer fuel consumption figures.

 

These cars, including my wife's 2015 Fabia have very little in the way of engine braking compared to older cars with far fewer electronics, computers and fancy engineering of the ancient ICE technologies.   In the Ren-No! I left an uphill dual-carriageway in 5th (out of 6) manual gears on a narrow turn-off to an unclassified road and slowed so much that an amber waring message very briefly flashed up saying something about stalling but it never did even before I changed down a few gears, the computers rushed in to resolve the issue.

 

I also showed to my neighbour that follwing Ren-No!'s manual gear recommendations an those low revs didn't give fuel saving and it was all about micro or ore throtle pedal movements, being steady with the throttle pedal and perhaps use of cruise control, perhaps speed-limiter (but I never use such driver interference stuff as I like to drive (well or not) a car and not be a passenger or part-time driver sitting behind the steering wheel). 

 

The gearing in these 1.0 3-cylinder VW engine'd cars seem to be very low to cope with the engine having to pull modern heavier cars and perhaps five passengers and luggage, if you want fuel economy try holding the gears a bit long and getting the revs up a bit higher perhaps whilst still going through the gears in a brisk but not racing manner.  Following VW's recommendation for manual gear selection seems to me to be biased to far to engine saving, save the engine by timely, thorough engine oil and filter changes using very good quality oils and having the engine, and the rest of the car running well.  Same for if you are not concerned too much with fuel consumption as well.

 

Good luck.

 

[Ootohere]

!.2 TSI,s & 1.0 TSI,s  should not really be expected on start up or tick over, and with Anti-stall to behave exactly like a 1.0 TSI with a GPF.

[Nix2]

In my Fabia, Skoda engineers were extremely stupid when it came to the "Anti-Stall" aspect.

Fabia happily displays the green ECO leaf, and at the same time FORCES the driver (driving ECO) to press the brake pedal ADDITIONALLY at every third intersection... this is ECO, wear of brake pads, gasoline and the environment...

 

And what happens when you go down long hills (in the mountains) and use engine braking?

It's possible, but initially when you brake the engine to a speed of about 1200 rpm, fuel consumption is ZERO.

When we exceed (down) the speed of 1200 rpm, the fuel consumption of a rolling car is... - about 2.0L/100km...

 

Wonderful ecology