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Delayed Throttle Response, (w/ solution)

54K views 58 replies 25 participants last post by  lbjgh 
#1 ·
Delayed Throttle Response, no it's not your imagination.
(Bonus solution @ end of post)
Since I picked up our long-term X3 from the South Carolina factory last April, I've noticed an annoying delay in its acceleration. Everyone on staff who's driven it has too, echoing complaints that the X3 accelerates either one of two ways: too slowly or with your head jerking back. We've also seen comments on numerous BMW forums saying the same thing, all stemming from new BMWs equipped with the new eight-speed automatic transmission.
I believe it's a result of programming, not the transmission itself. Even so, a trip to the dealership resulted in an unsatisfactory "operating as designed" prognosis and no change in its behavior. This month, we strapped our test gear to the X3, and took a closer look.

Findings: During low-speed acceleration from rest, like on a stop-sign punctuated residential street, the X3 exhibits repeatable throttle delay and very non-linear acceleration. Applying a normal level of throttle results in essentially zero forward movement for over half a second. Then, it feels like a gear engages, and then normal acceleration begins. While we expect some delay in throttle application (and miss throttle cables dearly), the X3's is noticeably longer and it makes driving smoothly difficult.

How we tested: At our test track, we strapped in a Racepak data recorder that uses accelerometers and GPS information. It is a system primarily designed for drag racing classes like Pro Mod, Pro Stock, and Super Stock; essentially overkill for this test. We then restricted the movement of the gas pedal with tape so the pedal could be treated like an on/off switch, but would be limited to the low-speed acceleration one would experience on a residential street. Doing so eliminated any wavering a foot might do on the throttle; when it's on, it's on completely. We then wired a trigger that would mark the data whenever the throttle was applied. We then simulated stop-and-go residential street driving, doing both complete stops and "California" stops.




Results: The graph above shows one near stop and start. Time is on the X-axis, mph (orange) is on the left Y-axis, and longitudinal (acceleration) g is on the right Y-axis, in green. This shows a "California" stop where the X3 decelerates to 0.6 mph (longitudinal g jumps to 0 when the brake pedal is lifted). At this point, the throttle is applied to its set point -- seen by the white spike -- and the X3 begins to slowly accelerate. After 0.6 second, the acceleration rate increases substantially, evident by the change in mph and longitudinal g, and then normal acceleration begins. Keep in mind that throughout this change in acceleration, the gas pedal input hasn't changed.

This half-second delay phenomenon was evident throughout our testing. In the five-run sample above, there is a noticeable change in acceleration behavior despite an unchanging pedal input. In 10 tests, we saw an average 0.5-second delay from the time that the throttle was applied to the time normal acceleration began, counting the time from the trigger mark to the jump in longitudinal g.
We believe this half-second delay is the culprit of all the complaints. But now that we've found it, we have more questions: Why is it there? One theory suggests that BMW might be trying to curb quick, "jackrabbit" starts to save fuel economy, but that's just a theory. We also want to know what's causing it. But, most crucially, can we get rid of it?

Solution...

A new software calibration was just released for this engine:
SIB 24 02 12
Subject:
N52T/N55 with 8HP45: Delay in Engine Response
Model
F25 with either N52T or N55 engines and 8HP45 transmission up to 1/16/2012
Situation
When slowing down to lower suburban road speeds and then reaccelerating, a delay in engine response may be experienced
Cause
Unfavorable EGS and DME software calibration
Correction
Program the vehicle using ISTA/P 2.46.0 or higher
 
#6 · (Edited)
Evlengr doesn't either... I think he was just saying that its a similar situation...

This sounds like a lesser version of the great transmission debacle
Personally, I am yet to get home and drive our new X3, but my wife has mentioned the delay. From what Evlengr says, I'm sure trying to get BMW to admit a problem will be tough.. And from what you have said, it sounds like a few 'fixes' will be on the way to release soon... Personally, I would love a Dinan chip upgrade that also takes care of this completely... Either way, thank you to you BOTH for the great info thus far! :thumbup:
 
#27 ·
That sounds like the BS answer I got from the dealership until I showed them my BMW school certificate and asked if they taught me wrong. :bareass:
 
#11 ·
It is not about "skeptics". The point is that you could learn how to drive to compensate for the lag but that doesn't make it go away. There is only one EPA test for each model and year for which BMW wants so set DME programming in a way that they believe will maximize mpg. After the test and the published mpg results BMW has more flexibility to respond to owner complaints. Even though the lag extended through two model years, it ws only 10 calendar months from F25 initial introduction to the production change.
 
#17 ·
I'm still confused. I have a new custom ordered 2012 X3 28i that I picked up from the dealer on March 12, 2012. I definitely notice the throttle delay in this vehicle, but from what I've read in this thread the fix should have already been installed. So do I qualify for this programming udpate or not? I guess I'll need to contact BMW Service to be sure.

Dave
 
#19 ·
Just came home from a 40 miles trip back from work/dealer. I had the work performed and the the jerkiness is all gone. Granted, they removed all the transmission adaptation but even without it the power delivery from dead stop or just a slow rolling stop is buttery smooth and there is NO noticeable lag/throttle hesitation. Good job BMW!
 
#28 ·
I can confirm the programming 95% gets rid of this problem and greatly enhances overall drivability.

I am very happy with the results! I still notice a little jerkiness if you come to a full stop and the transmission has't grabbed 1st yet, but it is much much much better.
 
#30 ·
how long does it take?

Dear TJ -- how long does this SIB fix take to administer? Is it a while u wait deal at the dealership, or days, or...??? Any insights would be helpful.

I love my X3 '11, except for the lurch. It's like an old motorcycle with "valve-line lash" we used to call it,

Best,

Fast Marty
 
#31 ·
Dear TJ -- how long does this SIB fix take to administer? Is it a while u wait deal at the dealership, or days, or...??? Any insights would be helpful.

I love my X3 '11, except for the lurch. It's like an old motorcycle with "valve-line lash" we used to call it,

Best,

Fast Marty
It takes somewhere along the lines of 7 hours to download the software to your car. Most people have reported taking the car in the morning and receiving it the next day. (my experience as well).
It's so worth doing as the car is much easier to drive in low speed urban environments.
You can read what the guys on the 5 series pages are saying about it if you care:
Global Software Update - Thoughts on Throttle Delay and more
 
#35 ·
problem solved

Dear TJ,

You're a genius! Thanks to you, I now have a "real BMW" -- I went for my annual service (#1) and used the phrase you suggested: "delayed throttle response." In addition to the piddling stuff they did (oil chg/wipers/blah blah), they held the car overnight and did the software thing with the SIB 24 02 12. Just picked up the car a few hours ago.

Holy cannoli. From 0-20 mph or so, the car leaps out of the chute like a bronc. No delays, no hiccups, no sense that the transmission is scratching its head trying to pick a gear, no sense of "drive line lash" like the old motorcycles had when the chain wasn't properly tensioned.

Like a champ -- that's how it runs.

Thanks a million for the advice.

Now I gotta reprogram all my radio stations and phones, but a small inconvenience for now owning what I expected I'd own when I picked the X3.

Brilliant!

Best,

Fast Marty
 
#38 ·
i spent a little time before dinner re-inputting my radio presets, pairing the phones and checking to see what else had been deleted. It took just a few minutes and now i can't wait to take 'er out for a spin today. i love the car more than ever. i am unsure why bmw handles it in this kind of ad hoc way, but thanks to TJ I got the fix and i'm a happy camper.
 
#39 ·
Marty, I'm glad you're happy with this tsb repair.

I almost crossed the x3 off my shopping list because of the throttle delay but after doing research I found a third party vendor that had a solution for the programming fault so I ordered my car.

I ended up getting a 2013 with the update from the factory and was happy I didn't have to monkey with a brand new car. :)
 
#40 ·
Delayed throttle resp[onse

Thanks for the update on this subject.Have experienced similar issue on my 2011X3 3.5xi and will raise it with the BMW SA in Orlando when I take my car in for first service in a couple of months. Appreciate the extensive information and will let you know the outcome when problem is addressed.
 
#43 ·
For me, it does seem like "sport" mode -- in fact, since I got the car back from the dealer friday afternoon, i haven't put it in sport mode yet -- no need, in any driving situation. interestingly, highway mileage is still pretty good: 28.6 mpg loafing along at 65 on a local highway. stop and go: still around 22-23 mpg. car has about 7300 miles.

so: no apparent downsides to the software update/upgrade. remember to use TJ's key words to your SA: "I have a delayed throttle response issue"...
 
#44 ·
Successfully got the software update yesterday, simply took the SIB in and they did the update with no argument. Got the X3 back later in the day.

I haven't driven it much yet, but it certainly seems better...
 
#45 ·
Mine has a build date of 2/2012. I happened to be at the dealer for something else and mentioned the throttle issue and showed him the bulletin. The response was that all the turbo's exhibit some sort of throttle delay and he couldn't do it to mine since the build date is later than the bulletin date. My throttle lag seems to be from a dead stop and not from the slowing down to almost a stop and hitting the gas pedal. So I wonder if mine actually has the newer software installed.
 
#46 ·
The n55 has basically zero turbo lag. Maybe ask if you can test drive a 2013 model to see if you can feel the difference. Based on my 2012 test drive I would personally pay for the TSB software update to get the driveability of my 2013 car. :thumbup:
 
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