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Stuttering

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Marcusbimmer
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Post by Marcusbimmer » Tue Jun 01, 2021 3:53 am

Help! Brand new Z4 M40i; had the dealer install LED door lights this weekend. Seemed to be fine after that. The next day (likely coincidence), during initial drive-away, there is a stuttering in the acceleration. Once I tapped the gas and it didn’t want to got then I did it again and it paused then went. Happened to my spouse today again. Scared her. It’s like a delay in gas pedal to acceleration. Anyone have any insight on this? Can the dealer remotely interrogate the ECU or do I have to drive 1.5 hours for this?
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Post by Obs-Com » Tue Jun 01, 2021 8:38 am

Get to the dealership for diagnostic check as needs to be plugged in. Don’t think this can be done remotely. Not aware of any similar issues with the M40i. Hope it gets sorted and be helpful to give an update once you know.
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Post by ori » Thu Jun 03, 2021 3:09 pm

Call BMW assist from within the car. It’s unsafe to drive like that. They will send a guy over and he can plug it in and find fault. Your car will be repaired quicker that way too.

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Post by ori » Sun Jun 06, 2021 7:22 am

Did you get to the bottom of this?

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Post by Marcusbimmer » Fri Jun 11, 2021 1:36 pm

So interesting.... Doesn't happen anymore. The ONLY thing that came to mind is that I filled the tank with PetroCan 94 gas at a station which normally probably doesn't sell a lot of 94 grade. That's the ONLY thing I can think of that was different. BUT, it didn't start until abou halfway into the tank so that doesn't make obvious sense either.
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Post by ori » Mon Jun 14, 2021 12:05 am

Sounds like it was the fuel.

Only fill it with the good stuff!

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Post by Z4monster » Fri Aug 06, 2021 6:07 pm

Hey, has this problem gone away for you or has it happened again? I ask as mine has been doing this intermittently for a while. Feels like the first inch of travel isn't doing anything on the accelerator then if you persist it goes OK.
It's occurred a few times over several months but the car hasn't been getting driven that much recently. The fuel isn't the issue as this is new fuel this week and is from a reputable station.

It's going for oil service to BMW so they're going to check it out while they have it.
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Post by Z4monster » Wed Aug 18, 2021 1:29 pm

Z4monster wrote: Fri Aug 06, 2021 6:07 pm Hey, has this problem gone away for you or has it happened again? I ask as mine has been doing this intermittently for a while. Feels like the first inch of travel isn't doing anything on the accelerator then if you persist it goes OK.
It's occurred a few times over several months but the car hasn't been getting driven that much recently. The fuel isn't the issue as this is new fuel this week and is from a reputable station.

It's going for oil service to BMW so they're going to check it out while they have it.
UPDATE: Car went to local dealer last Friday and they had to keep it over the weekend. The car had logged faults with the throttle position sensor and they replaced it after getting parts Monday. Car is back in rude health again and all appears fixed. As it was an intermittent issue I hope they've managed to find the fault first time.
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Post by Sladester100 » Thu Feb 03, 2022 3:01 am

Ooh.

Apols’ for the old thread revival

Interesting…
Ive experienced this a few times. Each when it was cold and very soon after starting, I assumed initially as yo did that it was fuel related as coincidentally had used some cheap stuff from a local garage that had a reputation (found out afterwards typically).
My latter assumptions were engine temp related and I wondered if was somehow related to the computer protecting the engine when cold and reducing throttle response / revving but reading comments here that’s not really safe and unlikely to be “a feature” so perhaps I’ll book it in for a diagnostics.

Did you find the revs dipped slightly as one of the times I found that, and it almost seemed a bit “starved” hence considered dodgy fuel.
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Post by Z4monster » Fri Feb 11, 2022 8:50 pm

Sladester100 wrote: Thu Feb 03, 2022 3:01 am Ooh.

Apols’ for the old thread revival

Interesting…
Ive experienced this a few times. Each when it was cold and very soon after starting, I assumed initially as yo did that it was fuel related as coincidentally had used some cheap stuff from a local garage that had a reputation (found out afterwards typically).
My latter assumptions were engine temp related and I wondered if was somehow related to the computer protecting the engine when cold and reducing throttle response / revving but reading comments here that’s not really safe and unlikely to be “a feature” so perhaps I’ll book it in for a diagnostics.

Did you find the revs dipped slightly as one of the times I found that, and it almost seemed a bit “starved” hence considered dodgy fuel.
When mine does this it feels fuel starved for a second or two and then picks up OK. It only happens from a complete standstill. E.G. at the lights and doesn't have any issue when on the move. Pulls like a train as normal at full revs once moving. I've tried stopping and restarting the engine and even locking the car. Doesn't usually make any difference. Then it will suddenly stop doing it again and go back to normal behaviour. My car has definitely been up to full temp when it's done it so not just a cold start issue.

It went back to BMW again after they replaced the throttle position sensor. This time they found no faults and couldn't replicate it. Very annoying really.

It only does it occasionally and doesn't last long but does annoy me when it happens.
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Post by motorknut » Fri Feb 18, 2022 6:30 pm

Hi all, I was directed to this thread after seeking help on bimmerpost.

Throttle hesitation has been reported by Supra owners too. I’ve been wondering why I hadn’t seen any complaints online from z4 owners (till now).

My own unit is experiencing this intermittently. I also have an intermittent long crank start up issue, and I’m starting to suspect they are related.

From day 1, my car has had a long crank start up, around once every 2 months. Bimmerlink shows shadow codes pointing to HPFP and Low fuel pressure.

Late last year (about a year into ownership) the car started demonstrating a throttle hesitation.at first I thought it was my imagination cos it happens so momentarily, I would let off the gas, Wait. And try again, and it would be fine.

I realised it was not just my imagination when one day, I was stopped facing upwards on a slope, waiting to make a turn. I stepped on the gas and the car did not move (or roll back) but the rpms started bouncing and the engine sounded weird. I braked, waited a few seconds and Tried the gas and it was fine.

I have run a sensor log using bimmer link, and it shows that the fuel pressure fails to rise for the first 1-2 seconds that the accelerator is depressed. Then suddenly the pressure kicks in.

These are my observations:
  • Hesitation occurs within about 500m of driving from start up.
  • Time engine has run doesn’t seem to make a difference, as I’ve tried letting car warm up too. Still occurs.
  • Not seemingly related to traction as roads always dry for my experiences.
  • Power resumes after about 1-2 seconds without needing to depress the pedal much more
  • Almost always occurs only once during a drive. Once, occured twice in one drive.
  • Has occured twice in a single day, different drives.
  • both cold or warm starts.
  • both flat or on upwards inclines.
The feeling is like fuel starvation, and I wouldn’t expect rpms to bounce otherwise. I’m having to send my car back into Toyota, but previously they picked up nothing on their scan tool and it’s almost impossible to replicate it on demand. My guess is hpfp mechanical issues.. at least I hope it’s just that. A software fault would be impossible for Toyota to fix on their own. Before seeing this thread, I started to think it was a Toyota tuning issue

The throttle hesitation leaves no shadow codes when I check with bimmerlink. Only the long crank start up triggers hpfp and valvetronic threshold warnings (the latter is a new development)
Last edited by motorknut on Sat Feb 19, 2022 3:59 am, edited 1 time in total.

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Post by motorknut » Sat Feb 19, 2022 3:18 am

Z4monster wrote: Fri Feb 11, 2022 8:50 pm
Sladester100 wrote: Thu Feb 03, 2022 3:01 am Ooh.

Apols’ for the old thread revival

Interesting…
Ive experienced this a few times. Each when it was cold and very soon after starting, I assumed initially as yo did that it was fuel related as coincidentally had used some cheap stuff from a local garage that had a reputation (found out afterwards typically).
My latter assumptions were engine temp related and I wondered if was somehow related to the computer protecting the engine when cold and reducing throttle response / revving but reading comments here that’s not really safe and unlikely to be “a feature” so perhaps I’ll book it in for a diagnostics.

Did you find the revs dipped slightly as one of the times I found that, and it almost seemed a bit “starved” hence considered dodgy fuel.
When mine does this it feels fuel starved for a second or two and then picks up OK. It only happens from a complete standstill. E.G. at the lights and doesn't have any issue when on the move. Pulls like a train as normal at full revs once moving. I've tried stopping and restarting the engine and even locking the car. Doesn't usually make any difference. Then it will suddenly stop doing it again and go back to normal behaviour. My car has definitely been up to full temp when it's done it so not just a cold start issue.

It went back to BMW again after they replaced the throttle position sensor. This time they found no faults and couldn't replicate it. Very annoying really.

It only does it occasionally and doesn't last long but does annoy me when it happens.
Don’t think it’s the throttle position sensor, cos I have the pedal angle tracked in my sensor log (for my Zupra) and it shows the pedal is depressed, but it’s the fuel pressure that doesn’t rise. In fact, it dips slightly below idle levels. This is for about 1.5-2 seconds, then pressure shoots up.

Have you had any luck since with the bmw dealer?

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Post by BMWZ4MC » Sat Feb 19, 2022 4:26 am

I don’t know if there are any Supra forums in Aus, but it’s seems to be a very popular car here in Sydney (I usually see several in a week). It might be worth seeing if anyone has experienced the same problem.
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Post by motorknut » Sat Feb 19, 2022 8:52 am

BMWZ4MC wrote: Sat Feb 19, 2022 4:26 am I don’t know if there are any Supra forums in Aus, but it’s seems to be a very popular car here in Sydney (I usually see several in a week). It might be worth seeing if anyone has experienced the same problem.
Thanks. There are a number of Aussie supra owners on the MK5 forum, but i didn’t notice any contributing on the throttle hesitation thread so far. Fair number of US owners reporting it.

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Post by Z4monster » Sat Feb 19, 2022 5:42 pm

motorknut wrote: Sat Feb 19, 2022 3:18 am
Don’t think it’s the throttle position sensor, cos I have the pedal angle tracked in my sensor log (for my Zupra) and it shows the pedal is depressed, but it’s the fuel pressure that doesn’t rise. In fact, it dips slightly below idle levels. This is for about 1.5-2 seconds, then pressure shoots up.

Have you had any luck since with the bmw dealer?
It hasn't been back to BMW since my last visit. To be honest I was pretty annoyed with them. Their attitude was 'We can't see a computer fault so we can't diagnose the issue unless it's occurring when we have the car' Also 'Can you not bring it in when it's happening?'
Err, it's intermittent and I could be 30 miles form you when it happens. Also it could stop doing it on the way to you, so the answer is NO! I can see their point but less than great customer service IMO.

Unless it throws a dash fault then I'm basically stuck with it happening from time to time.

Interestingly, it seems to happen less with higher octane fuel onboard although that could be completely coincidental. Next month I'm back in the office again so the car will be getting more usage. Let's see if it starts occurring more frequently. If it does, BMW will be getting the car until they find the fault.
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