Hi. I have a 2009 Octavia 2ltr diesel estate with the BKD engine. Just recently on occasion the pressing of the throttle whilst on the move has resulted in no acceleration. It's just as if you had taken your foot off the throttle. The engine drops to tickover and the glow plug warning light flashes. Occasionally re pressing the throttle makes the car accelerate again with the light flashing and on others it doesn't accelerate. Occasionally turning the engine off and then back on temporarily cures the problem for it to only return. No OBD codes are left. I've changed the throttle body and the throttle pedal/switch but this hasn't cured the issue. Has anybody on here had this same issue and cured it permanently? 

You need the stored fault codes but I suspect a faulty pedal position sensor (accelerator pedal is "fly by wire").

No codes are stored unfortunately. I've replaced the throttle pedal and it's switch already and still the fault persists. 

I have this same issue with cega engine and can't figure it out either
It's as if the pedal was unplugged, turn car off and on and it will work again for sometimes a few weeks before happens again, today had it 4 times

Hi Dallan. I've lost all confidence in my car. I'm going to change the brake light switch to be sure that that isn't sending an iffy signal which in turn would cut the throttle and then I will have to get an auto sparky to check the wiring and connectors for breaks or corrosion. I've read that connector corrosion can be an issue possibly stopping the throttle pedal getting its full 5 volts or just incorrect ecu to throttle pedal signals. 

On 05/03/2021 at 16:48, Moorside said:

No codes are stored unfortunately. I've replaced the throttle pedal and it's switch already and still the fault persists. 

 

Yes they will be but dont expect to find them using a generic OBDII  reader, you will need VCDS or similar.

 

It really will pay for itself in avoiding playing parts bingo not to mention the time saving and avoiding frustration.

Hi J.R. We've had a Snap on vcds on the car. No codes are shown. I think the problem is is that with the engine off and then on again the fault and dash warning light reset. I'll try reading the faults when the glow plug light is showing, the vehicle has faulted and with the engine running. 

I've used vcds and never any errors stored after it happens so it's most likely a physical issue

Never thought of brake light switch it does seem similar to left foot braking now you mentioned that

If it's anything like the ITE braking system on a 2006 1.9 PD, the brake light switch is a bolt on magnetic sensor on the side of the master cylinder which detects piston movement.

It's exactly one of those hard to reach horrors. I'll have this replaced, take it for a drive and go from there if it's still faulting. After that it'll be a call to the auto electrician to to do voltage readings to and from the throttle pedal, check all earth's and block connectors. 

I believe a faulty switch on the clutch pedal will also have the same effect of limiting throttle, so check that out at the same time.

 

Thanks and will do. 

Rather than replace unnecessarily just open the tailgate, stand by the driver's door and with the ignition on step on the brake pedal to check for correct brake application sensing by watching the high level brake light.

 

I have left foot braked whilst driving (before I found out it doesn't work on this model) and noticed the engine dropping to presumably no power rather than idle (fuel is cut when coasting for economy) but never had a glow plug indicator flash so I'm not convinced your problem lies with the brake switch.

 

I would be searching the net for reasons the glow plug indicator would flash on VAG cars especially models using the BKD engine but don't discount other engines whilst searching for clues.  Other than that chase a wiring/connector fault between the accelerator and ECU.

 

Accelerator position can be monitored real-time using diagnostic tools to check for full and correct reading.

 

Other things that may be involved MAP/MAF and associated wiring/connections.

 

Once the fault is triggered does road speed/gear have any bearing? e.g. if you pulled over immediately once faulting occurs does the accelerator and glow plug indicator still malfunction whilst stationary in neutral and no other controls operated?

Hi. Thanks for your post. The brake lights are operating as they should. Left foot braking shuts the throttle off abruptly. I'm yet to get a conclusive answer to why the glow plug light flashes. Most common reason cited is that the break lights are not working. The fault can arise just setting off in 1st gear at any pace from rest ie from a junction or any gear at any speed with including 70mph in 6th. 

Same here it is very intermittent haven't had it for ages then four times on Saturday hence I went looking and found this post

Driving along and it's like there is no accelerator pedal, engine goes down to idle as the car slows

Car stopped and pedal does nothing

Turn car off and on and it starts working again, also turn off and on while rolling/coasting fixes it

Don't think it's engine as mine is different

Moorside you said you replaced the pedal did you do the basic adaptation sequence in vcds after? Wonder if that would help

I had master cylinder changed a while back for a different issue but don't know if the brake switch was done at the same time

The mystery continues...

 

Dallan

I'll post when I get to the bottom of it. 

2 hours ago, MicMac said:

Rather than replace unnecessarily just open the tailgate, stand by the driver's door and with the ignition on step on the brake pedal to check for correct brake application sensing by watching the high level brake light.

 

 

Usually the brake switch has 2 sets of contacts, one for the lights and one for the ECU so this may not test it fully. This is so the car can verify itself and give a code for a faulty switch if required.

Thanks again. I'll replace the switch which as you know is situated under the servo in the engine bay with a genuine Skoda item to be fully happy that this isn't an intermittent fault with the item. For £23 it'll be worth it. 

https://www.youtube.com/watch?v=cjqutqtgiTk

 

https://www.youtube.com/watch?v=xkAcN7FRCO8

 

There are plenty of examples on the tube of problems like yours, last one I viewed was caused by injector wiring chafing.

Edited 10 March, 20215 yr by MicMac

Thanks. I'll check them out. 

youtube videos not quite the same, the glowplug only flashes for a second when the throttle stops working then goes out again, both the videoes had flashing all the time, and they would probably have faults stored if they scanned em

Hi. My glow plug light flashes continually when the throttle stops responding. It resets once the engine is turned off but no faults are stored. My car is at my local VAG independent garage now where the brake light switch is being changed, the glow plugs changed as one of them is intermittent and whilst on a new injector loom is being fitted as the connectors apparently go brittle which in turn could mean that the loom itself may do the same. A you tube clip suggests that the loom can cause problems. Worth a punt whilst the top is off and access is easy. Once the vehicle is back if the fault shows again I'll have the codes read whilst the engine is running and the glow plug light is flashing. 

On 10/03/2021 at 09:45, Dallan said:

youtube videos not quite the same, the glowplug only flashes for a second when the throttle stops working then goes out again, both the videoes had flashing all the time, and they would probably have faults stored if they scanned em

 

Hi. Did you get to the bottom of the intermittent non responsive throttle pedal on your car? I've just drove mine back from the garage albeit a short journey and it appears to be fine. I'll know more later when it's on a lengthy town drive. I replaced an injector that was a little weaker than the other 3 and whilst the cover was off I replaced the injector wiring loom as this has been mentioned on this forum. Additionally to that the servo attached brake pedal switch has been changed due to this being mentioned on many VAG forums. There was a lot of corrosion/crud between the switch and the servo which may have affected the switches operation and gave wrong signals that could have caused the problem that we have/had. 

6 hours ago, Moorside said:

Hi. Did you get to the bottom of the intermittent non responsive throttle pedal on your car? I've just drove mine back from the garage albeit a short journey and it appears to be fine. I'll know more later when it's on a lengthy town drive. I replaced an injector that was a little weaker than the other 3 and whilst the cover was off I replaced the injector wiring loom as this has been mentioned on this forum. Additionally to that the servo attached brake pedal switch has been changed due to this being mentioned on many VAG forums. There was a lot of corrosion/crud between the switch and the servo which may have affected the switches operation and gave wrong signals that could have caused the problem that we have/had. 

no i haven't gone back at it yet, as its not being driven much anyway with lockdowns etc. and anytime i have driven it since been ok

interesting about the brake pedal switch, i might do that, do you know the part number by any chance?