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Discussion Starter · #1 ·
Hey guys,

Am having a weird stalling issue with my 2008 Gallardo Spyder.

When I brake, the car revs all over the place and stalls occasionally. This only happens when I brake. It drives perfectly when not braking. Very scary when I’m driving along, apply the brakes, and then stall in traffic!

The master cylinder and brake booster have been replaced, along with one throttle body. Brake booster was used, and the master cylinder and throttle body were brand new. The brake pedal is stiff when the engine is not running, but sinks considerably when I start the car.

Here’s the weird part: when I remove the brake light switch, everything goes back to normal. It doesn’t rev erratically or stall when I brake. It drives perfectly and brakes normally. Never stalls at all.

What could this possibly be?

Thanks,
Drew
 

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2011 LP560-4 Spyder / Blu Fontus
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My immediate thought was clutch, but after I read on and you describe how it goes away it seems more of an electrical issue. What made you think to remove the brake light switch, and when was the other work completed (BB, MS, and TB) and how much, if any, time passed before this all started happening??
 

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Discussion Starter · #3 · (Edited)
All 3 parts were replaced within the past few months, after it started stalling. After all of that, my tech thought that, since it kept happening and happens only when I press the brake pedal, let’s take out the brake pedal switch and see if that solves the problem… and it did. But now I have no brake lights or anything else that switch controlled.
 

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OK, so the stalling issue prompted the diagnosis and replacement of those parts, which makes sense. I still would have been suspicious of the booster (being used) BUT, the next step removing the brake switch and finding the issue gone eliminates that suspicion. Now is when you need the electric schematic, wiring diagram to see what could possibly be in that brake circuit that could be pulling voltage (or shorting it) to something that could cause interference or feedback with some other signal voltage. Example: say the brake switch also sends a signal to the ECM which compensates for the vacuum pull from the booster by slightly ramping up the signal to the throttle bodies (not sure if that even happens in these cars but just to illustrate how the brake switch may be responsible for more than just simply turning on your brake light)
 

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So you didn't have any fault codes initially? You might say then why is everything fine when the brake switch is just simply removed, there's no signal going anywhere...... If, removing that switch sets a code then there may be another component in the system Expecting to see that signal, and upon seeing a drop in RPM caused by brake booster operation (different signal) it goes to a default, overriding the signal it is not seeing, compensates, and the car runs fine, but not optimal. Or, it's a defective component that is not handling the signal properly. In any case, obviously that's a tough one that will never be diagnosed by someone not working on the car unless they've experienced this exact issue. I hope this adds to the thoughts on it and your Tech gets to solve it for you ❗
 

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Discussion Starter · #6 · (Edited)
Thanks very much for this info!

Yes, when the brake switch is removed, both the ABS and traction control lights come on, and the car never stalls and runs fine (with obviously no brake lights)! When the brake switch is replaced, both of those lights are gone and the car resumes erratic idling and stalling (only when braking to slow down the car - not every time - perhaps 20-30% of the time). The idle increases and decreases erratically when pressing the brake, then stalls.

Just to clarify - it only stalls when I put it into neutral and coast/brake while driving the car, but it never stalls when I’m completely stopped and idling with my foot on the brake pedal, in neutral.

I just wonder what this switch could be affecting that would cause the idle to bounce around and kill the engine!
 

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There you go, if it's not the brake light itself, there's likely a fault in the Stability Program. ABS or TCS system. Some cars have one Module that handles both, some have separate systems with a module for each. What I think is weird is that you're not getting a code right from the beginning of the whole issue. That would have definitely helped with the diagnostics so unfortunately you may have to get the book out on that one. Good Luck ❗
 

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Discussion Starter · #8 · (Edited)
Thanks again! Now I’m wondering if anyone else gets an ABS and traction control light errors when the brake light switch is disconnected and brake pedal pushed? If those errors do not appear, then that would confirm the diagnosis that something is going with my ABS or traction control system. Any one to give it a try and let us know?
 

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Discussion Starter · #9 · (Edited)
Well, took it out this morning for a drive and the RPMs were going up and down, engine started sputtering and then stalled, even without touching the brake pedal, so now I’m thinking fuel filter, idle control valve, or something else fuel-related? Maybe this whole idea around it being caused by the brake light was just a coincidence?
I still need to know if it’s normal for the ABS and traction control error codes to appear when the brake light switch is not plugged in and the pedal is pushed down…

 

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Hey guys,

Am having a weird stalling issue with my 2008 Gallardo Spyder.

When I brake, the car revs all over the place and stalls occasionally. This only happens when I brake. It drives perfectly when not braking. Very scary when I’m driving along, apply the brakes, and then stall in traffic!

The master cylinder and brake booster have been replaced, along with one throttle body. Brake booster was used, and the master cylinder and throttle body were brand new. The brake pedal is stiff when the engine is not running, but sinks considerably when I start the car.

Here’s the weird part: when I remove the brake light switch, everything goes back to normal. It doesn’t rev erratically or stall when I brake. It drives perfectly and brakes normally. Never stalls at all.

What could this possibly be?

Thanks,
Drew
Simple question but have to ask-have you replaced the battery and ground cable? check for corrosion on the frame at the connection point? sounds like the booster is grounding out something else near by ?
 

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Discussion Starter · #11 ·
Thanks FL, but am now discovering that the car is stalling regardless of whether the brake light switch is in or out! It stalled 3 times within 10 minutes this past weekend, even with the switch out. The engine was actually choking and gasping for the first time, so am thinking now that it’s not anything in the electrical system. So I am going to have the intake and injectors cleaned out and charcoal canister replaced, along with fuel filters, plugs and coils. It’s time for all of that service anyway. Hope that does the trick!
 
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