Car stalls under hard braking???

[AtoB]

so about twice a week i have noticed that my car is stalling under certain circumstances.... when i brake hard, usually after heavy acceleration the car occasionally stalls... i've been to the dealer twice. they have no answers and can not duplicate the problem. i figured no huge deal until this weekend. i was braking hard turning into a parking lot and the car stalled leaving me with no power steering... i barely was able to steer the car and avoid hitting the curb. has anyone had this issue? any thoughts? this and the VANOS 'noise' issue... starting to not like my car very much.

[inTgr8r]

Never heard of that one.

[Erhan]

Might be a dumb question, but:

at what speed you're crusing before the hard braking?
which gear you're at?
what is your speed after the braking?

---

In general, I think during hard braking clutch should be in. The reason being, the engine revs won't be able to come down as fast as your deceleration rate. So in a way, while you're braking, the engine is pushing the car forward since the engine rev is higher than it should be (because it couldn't rev down as fast). I noticed this during a car control clinic. Doing 60mph at 2nd gear, and during very hard braking, the engine wasn't able to keep up with the deceleration.

[SCHMOUPE]

Originally Posted by erhanh

Might be a dumb question, but:

at what speed you're crusing before the hard braking?
which gear you're at?
what is your speed after the braking?

---

In general, I think during hard braking clutch should be in. The reason being, the engine revs won't be able to come down as fast as your deceleration rate. So in a way, while you're braking, the engine is pushing the car forward since the engine rev is higher than it should be (because it couldn't rev down as fast). I noticed this during a car control clinic. Doing 60mph at 2nd gear, and during very hard braking, the engine wasn't able to keep up with the deceleration.

Pretty much what he said but do u let go of the clutch when braking hard?

[inTgr8r]

Originally Posted by erhanh

Might be a dumb question, but:

at what speed you're crusing before the hard braking?
which gear you're at?
what is your speed after the braking?

---

In general, I think during hard braking clutch should be in. The reason being, the engine revs won't be able to come down as fast as your deceleration rate. So in a way, while you're braking, the engine is pushing the car forward since the engine rev is higher than it should be (because it couldn't rev down as fast). I noticed this during a car control clinic. Doing 60mph at 2nd gear, and during very hard braking, the engine wasn't able to keep up with the deceleration.

I don't agree.
Try it yourself, coast to a stop in neutral;
then coast to stop with the car in gear.

I can guarantee coasting to a stop in gear will be much quicker & shorter distance.

[Erhan]

Originally Posted by inTgr8r

I don't agree.
Try it yourself, coast to a stop in neutral;
then coast to stop with the car in gear.

I can guarantee coasting to a stop in gear will be much quicker & shorter distance.

Maybe. I didn't measure & compare stopping distances. But to my logic, if the engine is revving higher than it should, than it means it is pushing the car forward. I'd like to learn which is correct.

[Huz-Z]

If the engine stalls the same way under hard braking with the clutch to the floor and/or the car in neutral, you may have a fuel filter / fuel pump issue, or some other fuel system issue.

[AtoB]

at what speed you're crusing before the hard braking? 25-35
which gear you're at? not 100%... but i think i usually have the car out of gear or the clutch depressed
what is your speed after the braking?

[AtoB]

Originally Posted by Huz-Z

If the engine stalls the same way under hard braking with the clutch to the floor and/or the car in neutral, you may have a fuel filter / fuel pump issue, or some other fuel system issue.

i guessing the only thing i can do is wait for the problem to get worse and see if the pump fails... the dealer says nothing comes up when the scan the computer, and they can repeat the stall... wonderful.

[Dammmittt]

Sorry bro, hope it gets sorted out.

[dekaliber]

Originally Posted by inTgr8r

I don't agree.
Try it yourself, coast to a stop in neutral;
then coast to stop with the car in gear.

I can guarantee coasting to a stop in gear will be much quicker & shorter distance.

+1
When you coast in neutral, only the friction from wheel bearings, wind resistance, and the terrain act to slow you down. When you coast while in gear, the engine and drivetrain add resistance and slow the car down faster.

[AtoB]

... did it again tonight... i blipped the engine, pulled it out of gear, and then it stalled as i was coming to a stop...

[Blind32]

So it usually happens what you shift into neutral from a high rpm and the revs fall and keep going past the idle point? Like normally when the revs fall, they might dip a little below the idle point but them bounce back up. Can you tell if the engine just shuts off or do the revs fall all the way down, then it stutters then stalls? Any CEL or SES lights on? Might be a vaccum leak.

[AtoB]

Originally Posted by Blind32

So it usually happens what you shift into neutral from a high rpm and the revs fall and keep going past the idle point? Like normally when the revs fall, they might dip a little below the idle point but them bounce back up. Can you tell if the engine just shuts off or do the revs fall all the way down, then it stutters then stalls? Any CEL or SES lights on? Might be a vaccum leak.

no stuttering... just a smooth stall.... lights do come on the dash when it happens... i don't think anything that wouldn't normally do so if it stalled by driver error. but i'll look next time.... thanks!

[gizmo83]

I had something like this happen on another car and it was the ICV (idle control valve) Sometimes when the vehicle stopped it'd just shut off.

[Trev]

+1 to gizmo's suggestion.

Don't know if Z4's have a idle stabilization valve, but if they do take it off & clean out with carb cleaner or similar.

Other suggestions are battery voltage, a low voltage condition could cause ignition to shutdown.
Or bad engine ground.

HTH.

[blender]

Z4M has both a BRACKET IDLE ADJUSTER and an IDLE Regulating Valve.

I'd start with them and then move on to the fuel delivery system [pumps, filters].

good luck!

[alextoqiang]

Hi, I am having exactly the same problem with a 08 X5 4.8i (E70). I know this post is old. But I wish I can get some info how you sort it out.

[Finnegan]

Originally Posted by alextoqiang

Hi, I am having exactly the same problem with a 08 X5 4.8i (E70). I know this post is old. But I wish I can get some info how you sort it out.

Unfortunately I haven't seen a post from partipants on this thread in a long time. Sorry, but you're unlikely to get an answer from them.