What is the problem in sudden drops of RPM with EPC randomly going off and on and the engine icon flashing?

[Ognen]

Hello,

 

I am new to this forum and as I notice here you can find good info about most of the problems with the certain model of Skoda.

 

Few months ago, the EPC icon light began to lit, I had no problems at all until around 10 days ago when my car started to have sudden drops in RPM, and when pressing on the gas pedal, at random occasions, the car was unresponsive for a few seconds and then suddenly returns to normal state.

 

From two days ago, the EPC icon light randomly goes off and on and at the same time the engine icon light begins to lit constantly for a few seconds, and then begins to flash. At this point, when the car is in the first gear, by pressing on the gas pedal there are short oscillations with the acceleration, after putting it in second gear, the acceleration oscillation is longer, and after putting it into third gear, the oscillation lasts even longer in time all this no matter how deep I press the gas pedal, like the pedal is some kind of switch with 1 and 0.

 

Now, when I turn off the engine and restart it again, the engine icon lits constantly again for few seconds and then begins to flash, the oscillation problem is gone for few seconds while driving, so the driving is good for few seconds and then it appears again.

 

When the car is working in idle state, the engine is at 750 RPM but the car begins randomly to shake.

 

Before I go to a service, I really want to know what it could possibly be, the spark plugs only, the ignition coils, both or something more serious is at stake? I leave this to discuss it with you people.

[sepulchrave]

Is this a 1.2 or 1.4 petrol engine, which engine code please?

[Breezy_Pete]

Profile says 1.2 47kW 2007, so BME engine code.

 

Scan with VCDS or a handheld scan tool.

Post fault codes here. Fault lights mean there is fault information stored in the engine ECU; retrieve it please.

 

Check spark plugs.

Check brake servo vacuum pipe.

 

 

 

 

[Ognen]

Hi,

 

The engine is 1.2 petrol, I have stated that in my profile.

 

I have scanned the car with ELM327 scanner tool and it found P0303 and P0A11 error codes. I've found that P0303 is misfire detection in the third cylinder, and P0A11 is with the DC/DC converter problem.

 

I know that the spark plugs are definitely to be replaced because I saw their state.

 

For the rest I need guidance if possible.

 

Thank you for your effort in helping me.

[sepulchrave]

If the spark plugs are bad then one or more of the coil packs may also be damaged.

[Ognen]

Does it mean I have to replace only the ignition coil on the third cylinder, or on all together with the spark plugs?

[sepulchrave]

3 hours ago, Ognen said:

Does it mean I have to replace only the ignition coil on the third cylinder, or on all together with the spark plugs?

 

Just cylinder three.

[Ognen]

Thank you sepulchrave.

 

I need your opinion people about an offer I got from one of the car spare parts shops for my car by the chassis number and its specifications:

 

Denso 4701 IK16TT Iridium spark plug

Meat & Doria 10478E ignition coil

 

Are they fit for my car before I buy them?

[Ognen]

I have replaced all three spark plugs and the third cylinder ignition coil as Breezy_Pete and sepulchrave suggested, have cleared the error codes, all icons were off at ignition state of the car and after driving it for a while, the EPC light switched on again. Now, the RPM drops are gone, the car is moving smoothly but after some time driving the car with the EPC light on I have noticed again that, at random occasions, the gas pedal is unresponsive for a few seconds by pressing on it and then suddenly returns to normal state, i.e. the car accelerates normally.

 

After connecting the car on a diagnostic tool, no errors are present anymore although the EPC light is on.

 

Except to check the brake servo vacuum pipe as Breezy_Pete suggested, what else could possibly be on the queue to check with the EPC on and the symptom that I have experienced with the gas pedal lately?

 

P.S. Some suggest to check the car's throttle body itself, or the filters although I have replaced them all.

 

Thank you in advance,

Ognen

[cello]

You dont get this issue with oi burners!   Not helpful I know but I had a similar issue with a old 88 Gli Cavalier, turned out to be the ecu.

 

She ran great when everything was ok, real smooth but when the issue was present it was all over the place.  Good luck

[Breezy_Pete]

If the fuel filter is one that you've replaced, check that the pressure regulator part of it is the correct rating, visible on rearmost end of its alloy can under driver's side sill, near rear tyre. ECP has been known to mislead folks here. Phone camera can probably get a pic even if you can't get your head in right spot easily.

 

Also check that brake lights are all working.

 

And check brake servo hose.

[AnnoyingPentium]

I've had my BME coded Fabia exhibit these symptoms with both a duff throttle pedal (electronic, it's one unit) and a failing MAP sensor (there's no MAF on these).

 

It's all parts darts really. What "diagnostic tool" did you use? Ideally this wants checked with VAG-COM/VCDS.

[sepulchrave]

EPC lamp usually means an emissions problem, you may find that it clears itself now that you've fixed the misfire, try taking the car on a long fast drive on a motorway to clean the cat and probes.

[Ognen]

@Breezy_Pete I have checked the brake servo vacuum pipe and the fuel pressure regulator to a qualified mechanic and they are in great condition and working as expected they said. I guess they are telling the truth. Still the guys couldn't find the problem with the EPC turning on after resetting it.

 

@AnnoyingPentium I am using ELM327 scanner tool.

 

What brand/model do you suggest for VAG-COM/VCDS diagnostic tool for my car?

 

@sepulchrave I have added SONAX Octane Power additive, drove the car on a motorway, EPC is still on, but on the other side, almost two weeks now the gas pedal is responding normally. I will update on this.

 

Could the problem with the gas pedal be related to the fuel injectors if they were eventually dirty? I am guessing.

Edited 28 November, 2023 by Ognen

[Breezy_Pete]

VCDS Lite (freeware) is adequate for your car. Download from ross-tech.com.

Needs  a KKL/ FTDI  cable to interface between car and laptop. Very cheaply available. 

 

Test compression of each cylinder before doing much else.

[Ognen]

@Breezy_Pete Thank you, I will suggest cylinder compression testing and will update on this.

[Ognen]

Hello again,

I was at the mechanic to perform the cylinder compression tests as suggested by Breezy_Pete, they told me there is no issue with any of the cylinders. I didn't ask them for the values and that is why I didn't post them here.

On the contrary, the EPC is no longer lit for some time now(it turned off by itself), and the problem with the gas pedal being unresponsive for a few seconds returned again, so I have bought the VCDS HEX v2 and performed autoscan myself on the car and the following fault codes were listed:

 

Address 01: Engine        Labels: 03E-906-033-AZQ.lbl
   Part No: 03E 906 023 D
   Component: SIMOS91 1.2l 4V     9510  
   Revision: --H04---    Serial number: SKZ7Z0G4080262
   Coding: 0000071
   Shop #: WSC 13765 790 00000
   VCID: 204F5587F0C3EA8DA2-515A
   VINID: 91D4A0A411A90871011C21071C6384F86A

1 Fault Found:
16955 - Brake Switch (F)
            P0571 - 008 - Implausible Signal
Readiness: 0000 0100

 

 

 

 

Address 08: Auto HVAC        Labels: 6Q0-820-045-V1.clb
   Part No: 6Y0 820 045
   Component: Klimaanlage        X0840  
   VCID: 72EB6FCF3EAF281D84-515A

1 Fault Found:
65535 - Internal Control Module Memory Error
            00-00 - -

 

 

 

 

Address 09: Cent. Elect.        Labels:. 6Qx-937-049-C.lbl
   Part No: 6Q2 937 049 F
   Component: 0000 BN-SG.         2S36  
   Coding: 17422
   Shop #: WSC 13765  
   VCID: 3F8DF6FB3D7DB575BB-513C

1 Fault Found:
01598 - Drive Battery Voltage
            07-00 - Signal too Low

 

 

 

 

Address 15: Airbags        Labels: 6Q0-909-605-VW5.lbl
   Part No: 1C0 909 601 A
   Component: 0T AIRBAG VW51      0010  
   Coding: 12372
   Shop #: WSC 13765  
   VCID: 1E336B7F9AB7DC7D90-515A

1 Fault Found:
00532 - Supply Voltage B+
            07-10 - Signal too Low - Intermittent

 

 

The battery voltage when the engine is OFF is 12.6V, and when started it is 13.5V with everything turned off(like lights, conditioner etc.). Is it possible this to be the battery issue or something more serious?

Also, I am planning these days to replace the brake switch although it is working as expected.

 

I am a bit worried and need your help here.

Thank you

[sepulchrave]

13.5V with engine running is too low.

 

Replace the brake switch first, it's two switches in one and one part of it has failed.

[Ognen]

@sepulchrave Thank you, I also think that the battery should be replaced. I am afraid I don't understand what do you mean by "two switches", I know that there is one brake switch, very simple mechanism indeed.

[sepulchrave]

8 minutes ago, Ognen said:

@sepulchrave Thank you, I also think that the battery should be replaced. I am afraid I don't understand what do you mean by "two switches", I know that there is one brake switch, very simple mechanism indeed.

 

No, I mean it's a double pole switch, one pole does the brake lights the other pole sends a signal to the ECU, this is the part of the switch that has failed.

[Ognen]

UPDATE: Today I have replaced the battery, the ignition of the engine is now much faster, the battery voltage with started engine is now 13.75V, and when turned OFF, it is 12.7V and also made Throttle Body alignment with the VCDS.

I have also reset all DTCs, rescanned everything and VCDS did not find any errors except the aforementioned 16955 - Brake Switch (F). The problem with the gas pedal is still present.

Either the brake light switch needs replacement or the gas pedal or both. I will update on this after I replace the brake light switch first.

 

@sepulchrave

Quote

the other pole sends a signal to the ECU

This is possibly the reason for the unresponsive gas pedal, but also there is another thing that bothers me, and that is why the vehicle does not brake itself, only the gas pedal becomes unresponsive, I made measurements on a graph together with the throttle valve angle and the gas pedal, both values were not moving either way when the gas was stuck.

Edited 15 February by Ognen

[xman]

IIRC a faulty brake switch is a well known and common fault on the Mk1 fabia and other sister models and the symptoms  are a unresponsive throttle and engine management light. IIRC way back when I had a mk1 Fabia, Vagcom diagnostics used to report " implausible signal" (the 2 poles didn't agree)

 

As @sepulchrave says, get it changed. Its a dual pole switch, one pole for the brake lights and the other tells the ECU that braking is taking place so restrict the throttle signal. Its not expensive, quite easy to change, but sometimes requires a bit of adjustment once fitted.

 

Make sure you get the correct version for your car.

Edited 15 February by xman

[Ognen]

Thank you @xman.   Tomorrow I will replace the switch for the brake lights and see what happens next. I will update on this case.

[Ognen]

I have replaced the brake light switch thanks to @xman and @sepulchrave suggestion and the EPC light is gone for good. Also, the problem with the accelerator pedal is gone now. The battery voltage is even better now when the engine is started, 13.9V. Rescanned with VCDS and no errors found. I think the problem is solved and let this be of help for someone having the same problem.

 

Thanks to all for your help.