My M4 GTS continues to accelerate after I let my foot off the gas

[delfunk]

Has anyone experienced the car still accelerating once you let your foot off the gas for a couple of seconds under full acceleration? Another GTS owner has verified this with me as well. There are no fault codes and of course and they cant duplicate it. It's always when driving hard from 1-2 gear.

I'm thinking the water injection system is still shooting water and is malfunctioning or a faulty throttle body.

The BMW engineer thinks it's the turbos still spooling and air is getting into the intake. I told him impossible there is a throttle body and a blow off valve. He didn't like hearing that. Maybe the throttle body has an issue?

[aBMWfan]

Originally Posted by delfunk

Has anyone experienced the car still accelerating once you let your foot off the gas for a couple of seconds under full acceleration? Another GTS owner has verified this with me as well. There are no fault codes and of course and they cant duplicate it. It's always when driving hard from 1-2 gear.

I'm thinking the water injection system is still shooting water and is malfunctioning or a faulty throttle body.

The BMW engineer thinks it's the turbos still spooling and air is getting into the intake. I told him impossible there is a throttle body and a blow off valve. He didn't like hearing that. Maybe the throttle body has an issue?

It just happened yesterday in my standard m4. I think it's something to do with traction control

[delfunk]

I don't think it's the TC. That should cut the throttle. It's something else. How many seconds was your car accelerating for after you let your foot off the gas?

[aBMWfan]

Originally Posted by delfunk

I don't think it's the TC. That should cut the throttle. It's something else. How many seconds was your car accelerating for after you let your foot off the gas?

2-3 seconds

[delfunk]

Originally Posted by Bem4

2-3 seconds

That's exactly what I am experiencing. Any lights on the dash pop up or anything?

[CanAutM3]

Originally Posted by delfunk

Has anyone experienced the car still accelerating once you let your foot off the gas for a couple of seconds under full acceleration? Another GTS owner has verified this with me as well. There are no fault codes and of course and they cant duplicate it. It's always when driving hard from 1-2 gear.

I'm thinking the water injection system is still shooting water and is malfunctioning or a faulty throttle body.

The BMW engineer thinks it's the turbos still spooling and air is getting into the intake. I told him impossible there is a throttle body and a blow off valve. He didn't like hearing that. Maybe the throttle body has an issue?

First, "a couple of seconds" usually means about two seconds, this a hell of a long time for the car to continue to accelerate. Are you sure it is that long?

Second, the S55 does not have a blow off valve. Boost pressure is regulated through waste gates on the exhaust side.

Third, the engine throttling on the S55 is mostly managed through the Vanos/Valvetronic system and not with the throttle body.

Fourth, water injection by itself does not produce power, so even if the water injection system would be defective, it would not explain your symptoms.

[delfunk]

Yes, it's 2-3 seconds and its pretty intense and scary. I'm concerned someone will jump in front of me. My car has ceramic brakes and that still doesn't stop it while accelerating. There is a bigger problem here and I have no idea what it is.

[guess2098]

It doesn't happen to my m4. Do you have tune or any piggy back? Normally happens on my piggyback tune

[aBMWfan]

Originally Posted by guess2098

It doesn't happen to my m4. Do you have tune or any piggy back? Normally happens on my piggyback tune

It happened on my fully stock m4 yesterday, after gunning it around a right turn.

No lights on the dash.

[delfunk]

Originally Posted by guess2098

It doesn't happen to my m4. Do you have tune or any piggy back? Normally happens on my piggyback tune

No tune fully stock

[CanAutM3]

Originally Posted by delfunk

Yes, it's 2-3 seconds and its pretty intense and scary. I'm concerned someone will jump in front of me. My car has ceramic brakes and that still doesn't stop it while accelerating. There is a bigger problem here and I have no idea what it is.

Get it to another dealer ASAP, something is definitely wrong.

[jpdchicago]

Never had that happen in mine. Definitely does not seem right.

[FlyingLow78]

Other brands of cars have been affected by this problem due to floor mats that have gotten too close to the throttle pedal and interfered with its movement. Another possibility is a malfunctioning throttle pedal module (mounted at the pedal) or a sticking throttle plate.

I would check to see if the throttle pedal retracts properly when released. Try fully depressing it by hand with the car turned off and quickly releasing to see if it returns to its original position. Example:

[schnell325]

Get to a dealership immediately

[aBMWfan]

Originally Posted by schnell325

Get to a dealership immediately

It only happened one time, but I'm still concerned in that case.

My car goes to the dealer Tuesday. Will definitely ask about it!

[gingerbread]

Is this with DSC on ? Does it feel like continued acceleration or no engine braking ? Ive read somewhere in the training documents that is the DSC can adjust the level of engine braking based of many factors. It does this to not unsettle the rear end of the car with excessive engine braking. Some factors are rain, outside temps, cold tires and so on. Maybe some more info on what is happening environmentally, road conditions, are you turning, etc..



To clarify something you have said here and other threads:

S55 has no blow off valve/ diverter valve, uses the turbo wastegates, vanos and valvetronic to control excess boost... simplify put the excess boost pressure is let through the engine and out the exhaust aka the BRaAAAppPP Sound on first letting off the throttle.

It doesn't use its throttle valve in a traditional way, it's opened more then closed most of the time. Example at idle the throttle valve is opened and the valvetronic is controlling idle by valve lift (lift at the valve can be around .3mm at idle) basically each intake valve is a throttle valve.

The water injection doesn't flow through the throttle valve at all. There is 3 injectors in the intake manifold after the throttle valve directed at the intake runners.

Originally Posted by delfunk

Has anyone experienced the car still accelerating once you let your foot off the gas for a couple of seconds under full acceleration? Another GTS owner has verified this with me as well. There are no fault codes and of course and they cant duplicate it. It's always when driving hard from 1-2 gear.

I'm thinking the water injection system is still shooting water and is malfunctioning or a faulty throttle body.

The BMW engineer thinks it's the turbos still spooling and air is getting into the intake. I told him impossible there is a throttle body and a blow off valve. He didn't like hearing that. Maybe the throttle body has an issue?

[guess2098]

Originally Posted by gingerbread

:

S55 has no blow off valve/ diverter valve, uses the turbo wastegates, vanos and valvetronic to control excess boost... simplify put the excess boost pressure is let through the engine and out the exhaust aka the BRaAAAppPP

I like ur bbbaaarrrppppp.

[delfunk]

Originally Posted by guess2098

I like ur bbbaaarrrppppp.

Thank you Gingerbread for your comments. I think the GTS does have a blow off valve because I hear air shooting out of the system?

I have the car in M1 mode full sport with M dynamic mode on. I live in Cali so there is no humidity or wet roads. I never drive the car while it's raining. It has happened three times in 850 miles and BMW is baffled and thinks I "invented" this. I have had BMW experts look at it and they say no codes and we can't verify so pretty much tough luck. The only thing they can say is the turbos are still shooting air in to the engine. Makes zero sense to me.

Other owners experience this and someone will have an accident and someone will get hurt until they open their eyes. I plan on writing a serious letter to BMW NA President.

[gingerbread]

Once again NO S55 version has a blow off / diverter valve system.

Can you explain step by step the order of events leading up to the issue?

Example: Im pull away from a stop in first gear and roll into 100% throttle (80% or etc.) going straight ahead (no steering input or whatever input you are doing) and DSC is intervening or not. At about 7000 rpm I shift to second gear and let of the throttle 100% and .........

and again is the car continuing to gain speed (feel like its still making power) or is it holding the speed/rpm that you let off throttle at? no engine braking / deceleration.

live data / data logging, taking the tech for a ride, taking it to a dyno to recreate. Try a different dealer / BMW speciality shop and be open and try and give as much info as you can. Make time for the shop to look at the car... clear a whole day or week / weekend.

Originally Posted by delfunk

Thank you Gingerbread for your comments. I think the GTS does have a blow off valve because I hear air shooting out of the system?

I have the car in M1 mode full sport with M dynamic mode on. I live in Cali so there is no humidity or wet roads. I never drive the car while it's raining. It has happened three times in 850 miles and BMW is baffled and thinks I "invented" this. I have had BMW experts look at it and they say no codes and we can't verify so pretty much tough luck. The only thing they can say is the turbos are still shooting air in to the engine. Makes zero sense to me.

Other owners experience this and someone will have an accident and someone will get hurt until they open their eyes. I plan on writing a serious letter to BMW NA President.

[delfunk]

Full throttle in first I then shift to second and let my foot off the gas after being in second gear full throttle for a second or two and the car keeps on accelerating. No traction control nothing. I am going straight.

[delfunk]

Bem4 please make sure you have them put it on the repair order so there is a record. BMW needs to know of these issues.

[Darth One]

Haven't had that issue but I do have to say that the throttle is the worst thing about this car. BMW really fucked it up.

That said, it's kind of the same thing as the mole on Cindy Crawford's face