Start/Stop Button "Press Clutch to Start Engine" Problem

[S4'ed]

There are a couple of things that are going on that can contribute to the issue. Let me explain how the switch works, there is a plunger inside the master cylinder that has a magnet on it, the master cylinder in itself has three separate switches on it (as described earlier) which are activated when the magnet passes across the switch. I do not know that exact reason for failures, however I suspect that it is either

1.) The fluid in the circuit has air in it and is not allowing the plunger to move far enough to activate the switch or
2.) the magnet becomes weak and is no longer able to trigger the switch

You could try to do a full bleed of the clutch and remove all of the air out of the system, a vacuum bleed typically works best, or you can replace the clutch master cylinder. There is the possibility that the clutch master cylinder piston can have a bad seal too, this scenario will may keep the plunger from moving all of the way.

An air bubble in the system will let the piston move further than normal, because the air compresses.....so that rules out an air bubble as the root of the problem. As per the Audi TSB, if something in the clutch mechanism is worn, and binding-up, that is what prevents the full normal travel of the master cylinder piston, which then fails to trip the start-switch.

For people who resolved this problem by replacing the Master Cylinder, I suspect Audi revised this part to move the start-switch "in" a little, to require slightly less piston (and clutch pedal) travel before the switch trips.

[A4Ultrasport]

One more to add to the list. My 2012 S4 is on the original factory clutch, and has 45K miles on it. I've started noticing that the car won't start unless I really press the clutch pedal firmly to the floor (a big change from what I've had to do over the previous four years of ownership). So far this seems to happen most frequently when the temps are above average (85 degrees or more). My clutch has a small amount of chatter when engaging from a stop, but otherwise my clutch seems to be perfectly healthy.

I find it interesting that folks seem to have this problem with factory clutches, aftermarket clutches, both new and heavily used. I realize I will have to replace my clutch some day, but don't want to unnecessarily if it won't ultimately fix this problem ... I have CPO warranty coverage for another two years, but don't want to engage my dealership on this issue yet until I have a better idea of what is causing the problem.

Hoping someone finds a definitive answer on this.

[Hofahome]

Well crap. Mine started doing it this past week, exactly like how everyone describes. Mine is a 2013 at 43k miles, stock clutch. Never tracked. Not slipping unless hard 1-2 shift. No chatter.
I have a JHM stg 4 clutch and USP SS clutch line in my garage that I was going to get installed in 3 weeks. Looks like I am going to have to make an appt with the stealership to get it looked at before I upgrade.
How is it that I had a 20 year old Ford Escort that never had issues with the mt after 200k miles, but this seems to be a common issue on a 3 y/o $50k car? Fuck you Audi.

[SportVier]

My 2013 just started doing this at 45k. Let's see...

Sunroof leak at 30k.
Water pump failed at 40k.
Starting issue at 45k.

Was planning to keep this one a while, but it is not inspiring confidence.

Vorsprung durch Technik. Yeah...

[S4'ed]

And you assumed an Audi was as reliable as a Toyota???????

[SportVier]

And you assumed an Audi was as reliable as a Toyota???????

That is a lot of question marks... I assumed the B8.5 S4 was no less reliable than a B7 RS4. I was wrong. My bad.

[Jano4]

Currently having this similar issue but does not matter how forcefully I press the clutch. Does anyone also get "Stabilization Fault" on there dash when trying to start?

[skynetop]

I now have this issue at 79k. They first replaced the battery, but then I brought it back as it returned. I have to stand on the clutch for the car to start. Never had any issues with any gears, car is stock and I never launch it.
I got some quotes to replace the clutch and fw but I am thinking it may be just the cylinder.

[sh!tmagnet]

The guys over at 3zero3 have developed a plug and play solution for the clutch safety switch that will be released in the new year. They will explain it further but throwing parts at it isn't going to fix it long term.


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[haynstyle]

The guys over at 3zero3 have developed a plug and play solution for the clutch safety switch that will be released in the new year. They will explain it further but throwing parts at it isn't going to fix it long term.


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Does 3zero3 have a fix for this yet? I upgraded my clutch about 6 months ago, Southbend Stage2 and havent had any issues and then this happened. Popped out of no-where and cant figure out why?

[UmbroVR6]

Mine started doing this. Looking for solution. Already replaced slave but didn't fix it. Going to do the master cylinder now. Anyone know anything new? Updates?

[DBFL]

Mine started doing this. Looking for solution. Already replaced slave but didn't fix it. Going to do the master cylinder now. Anyone know anything new? Updates?

The modified slave cylinder from jbullin2 is the way to go.

[UmbroVR6]

Anymore info on modified slave by jbullin? Thanks

[DBFL]

Anymore info on modified slave by jbullin? Thanks

How much more info is needed? It's a stock slave with a 1/4" longer rod. And it fixes the problem.

[Jay@JXB]

Mine started doing this. Looking for solution. Already replaced slave but didn't fix it. Going to do the master cylinder now. Anyone know anything new? Updates?

Yo! PM me or find me on Facebook (Jae Barrington) my extended length slaves fix this with 100% success rate :)


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[UmbroVR6]

How much more info is needed? It's a stock slave with a 1/4" longer rod. And it fixes the problem.

relax dude, i don't know jbullin and in this thread other than your post i saw no mention of it. all i wanted to know is what was modified to the slave. thank you, i've contacted jbullin to see how i can get the longer rod.

[DBFL]

relax dude, i don't know jbullin and in this thread other than your post i saw no mention of it. all i wanted to know is what was modified to the slave. thank you, i've contacted jbullin to see how i can get the longer rod.

I wasn't being a dick, although tone is hard to interpret on an internet forum. I legitimately thought you were asking for more specifics about the slave cylinder itself.
Anyway, Jae will get you taken care of. He's easy to do business with.

[TXautobahn]

Just bought one from him, great guy. Will be installing it in the next few weeks once I have time.

[GLIsten]

After many months of agonizing over this issue, I'm happy to vouch for the extended slave rod from jbullin2. Installed two weeks ago and better in every way since. Proper starts, lighter clutch pedal feel, higher engagement point, rev matching more often now.

[UmbroVR6]

received mine on monday, haven't had a chance to put it in, maybe this weekend. i'll report back.

[lexcruiser]

Are you guys replacing the slave proactively with jbullin's before the issues surface?