Erratic throttle response when cold

[HPsauce]

Originally Posted by MikkiJayne

No brake switch error code on power-up either, so that must be a PF thing

Pretty sure I get it on my FL. Must check sometime.
Maybe my brake switch is faulty too.....

[steamship]

Originally Posted by MikkiJayne

When I fitted the replacement brake switch I got it in the perfectly wrong position (yes, there is such a thing!). It has two contacts - one normally open (for the brake lights), and one normally closed (for the ECUs). The ECUs expect to see both contacts change together so they know the switch is working. I'd managed to get it in just the wrong position so the normally open was open, but just enough pressure on it for the normally closed to also be open! The ECUs knew something was up so all got in a grump Wound the switch in another half turn and everything is fine now - no codes, and enough oomph from stationary to wake up the ESP I wish I'd figured this out before towing the FE home Steamship - that could well be your issue too?

Sounds like something I'll have to try. Question is, how did you test their open/close positions? Was it using VCDS, and if so, how, or just using a multimeter across the terminals?

[MikkiJayne]

I discovered it with a multimeter so since it was already in there adjusted it until it was right also using the meter, but you can see it in Engine measuring block 66 in VCDS too. Mine was only showing one bit changing when I pressed the pedal where there should be two. Once I'd wound it in half a turn both bits changed and everything was happy.

[HPsauce]

Originally Posted by HPsauce

Pretty sure I get it on my FL.

But no, I don't!
It was actually very difficult to get into the drivers seat and NOT put my foot on the brake pedal, but I managed it.
Did a VCDS scan and no errors, so I guess it really is a PF issue.

To repeat NO ERRORS. After nearly 4 years of niggling behaviour and the infamous 01119 error. Best Christmas present for a long time.

[HPsauce]

Originally Posted by MikkiJayne

I discovered it with a multimeter so since it was already in there adjusted it until it was right also using the meter, but you can see it in Engine measuring block 66 in VCDS too. Mine was only showing one bit changing when I pressed the pedal where there should be two.

Just tried that with VCDS. The switch was showing a value of 1000 when untouched.
A VERY LIGHT touch on the pedal (engine off) would change it to 1010 but the slightest bit more and it went to 1011.
That sequence could be reversed by lifting off very carefully.

With the engine running and servo operating it was just about possible to replicate the two stages with great care. But in practice they were near-simultaneous, and I'm sure that on the road they would be.

Does anyone know what those two switches are supposed to do when set correctly, i.e. are they meant to be very slightly apart and if so which way round?

[MikkiJayne]

Thats exactly what mine does now its adjusted properly. One set of contacts acts a mm or so before the other. I think this is deliberate so that the ECUs know whether you're pressing the pedal or letting it go, the same as the TCU knows which direction the F125 is moving.

[steamship]

Originally Posted by MikkiJayne

I discovered it with a multimeter so since it was already in there adjusted it until it was right also using the meter, but you can see it in Engine measuring block 66 in VCDS too. Mine was only showing one bit changing when I pressed the pedal where there should be two. Once I'd wound it in half a turn both bits changed and everything was happy.

Originally Posted by HPsauce

Just tried that with VCDS. The switch was showing a value of 1000 when untouched.
A VERY LIGHT touch on the pedal (engine off) would change it to 1010 but the slightest bit more and it went to 1011.
That sequence could be reversed by lifting off very carefully.

With the engine running and servo operating it was just about possible to replicate the two stages with great care. But in practice they were near-simultaneous, and I'm sure that on the road they would be.

Does anyone know what those two switches are supposed to do when set correctly, i.e. are they meant to be very slightly apart and if so which way round?

Thanks very much to both of you. I thought I was being clever when I replaced mine, by measuring how far the old one had been screwed into place. When I did the VCDS scan today, I was getting the 1010 with very little movement, but didn't get the 1011 until I pressed it much further. When I had the engine running, I was getting 1010 all the time. I lifted the pedal with my foot and it went back to 1000. That would explain why the ECUs aren't giving me full power after a gradual braking to a halt. The pedal is not releasing 100%.

Anyway, gave it a full turn, connected up and tried again. 1010 with the slightest touch and 1011 shortly after. With the engine running, same results. Haven't been out in the car yet, but just reversing it round to the front of the house felt so much freer than before.

[HPsauce]

This ancient thread (14th February 2013, 06:01 PM) is uncovering all sorts of intriguing little issues.

So, how many of us will be plugging in VCDS this weekend and checking Block 66 in Engine while toying with the brake pedal, engine off and on? Someone start a poll (separately please!).

Originally Posted by steamship

just reversing it round to the front of the house felt so much freer than before.

Sean, let us know how it behaves next time you go out.

[steamship]

Originally Posted by HPsauce

This ancient thread (14th February 2013, 06:01 PM) is uncovering all sorts of intriguing little issues.

So, how many of us will be plugging in VCDS this weekend and checking Block 66 in Engine while toying with the brake pedal, engine off and on? Someone start a poll (separately please!).

Sean, let us know how it behaves next time you go out.

There doesn't seem to have been many people with the issue... or they've never seen this thread. It was only because Mark made a comment about the brake switch that prompted me to mention the codes I was getting, with MikkiJayne reporting how she resolved it.

Will keep you updated on how the car responds.

[steamship]

Well, it's been a week now and the car has been used extensively for lugging loaded trailers around, and I'm happy to report that I haven't had a single instance of throttle hesitation.

Not only that, but it just feels so much easier to drive, and I get to hear that V8 burble more as it's more lively.

I haven't scanned it since, so have no idea if there's anything still lurking in the Engine, ABS or Transmission blocks.