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UPDATED::: Z4M S54 Engine Hesitation - POLL

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Does your Z4M S54 suffer from the engine hesitation from idle?

Yes, and I'd like it fixed
91
35%
It did, but it's fixed
15
6%
Yes, but it doesn't bother me
13
5%
Yes, but it only happens once in a blue moon
39
15%
No, I've never had this happen
100
39%
 
Total votes: 258

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Buzzard88
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UPDATED::: Z4M S54 Engine Hesitation - POLL

Post by Buzzard88 » Wed Apr 10, 2019 12:26 am

ph001 wrote: Tue Apr 09, 2019 4:09 pm
Buzzard88 wrote: Tue Apr 09, 2019 12:58 am I am not totally convinced this is a misfire though. I actually think it is just a really bad fuel / air preparation cycle.

So my understanding is that the DME is operating in closed loop when my problem occurring.
Yes, what you are essentially doing by stabbing the throttle from idle is transitioning from closed loop control (a/f ratio controlled by lambda sensors) to open loop control (a/f ratio controlled by ECU map against air flow meter signal). I'm just wondering that if by disconnecting the air flow meter the ECU never runs in the open loop state (because it's has no air flow information to allow it to do so), so you aren't going from one state to the other. I'm betting it stays in closed loop control all the time with the AFM disconnected.
This is a very interesting lead indeed and one worth pursuing a little. With the two TPS sensors replaced and no fault codes though I would have thought the DME would know when it wanted to go into open loop mode and would throw codes if there was drama doing so. But I am going to somehow look closer at this idea.

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UPDATED::: Z4M S54 Engine Hesitation - POLL

Post by Buzzard88 » Wed Apr 10, 2019 12:42 am

AndyBeech wrote: Tue Apr 09, 2019 7:49 pm When you disconnect the MAF the car reverts to the Alpha-N map, which I believe estimates air volume instead using the engine speed and TPS. Do some Googling on it but IMO disconnecting the MAF doesn't prove anything conclusive as it doesn't really help you narrow down if a sensor is giving you an issue as the mapping has changed.

Have you tried INPA / DIS yet, see if you can run some tests and check for error codes. I fear your going to end up replacing a lot of expensive parts for no reason. For example, the ICV replacement is pointless, it really just works or doesn't it's a simple valve that opens and closes as you would have seen. Cleaning it is good but I wouldn't waste money replacing it.

It's safe to run without the MAF connected but absolutely no reason to do so long term unless you've specifically had Alpha N tuned for your modifications, such as running a CSL airbox where you have no MAF for example.

Oh, INPA would be useful for checking your long term trim's/adaptations, see if there's anything untoward there
An interesting option to maybe get an Alpha-N map tune. So do you know if the closed loop mode is running with the Alpha-N map, the same Alpha-N map as when the MAF sensor is disconnected?

I Have not yet tried INPA or DIS as I am still waiting on my cable to be delivered, but very keen to do so.

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UPDATED::: Z4M S54 Engine Hesitation - POLL

Post by Buzzard88 » Wed Apr 10, 2019 1:28 am

BMWZ4MC wrote: Tue Apr 09, 2019 2:22 pm
Buzzard88 wrote: Tue Apr 09, 2019 4:14 am After looking for the post cat sensors I couldn't even find the cats. Now I feel pretty stupid as Australian cars are the Euro spec which apparently don't have cats at the headers, they are way back underneath the car.
Where are you based in Aus?
Was in Newport until recently moving to Coal Point, Lake Macquarie. Nice to see a local.

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UPDATED::: Z4M S54 Engine Hesitation - POLL

Post by AndyBeech » Wed Apr 10, 2019 2:12 am

Buzzard88 wrote: Wed Apr 10, 2019 12:42 am
AndyBeech wrote: Tue Apr 09, 2019 7:49 pm When you disconnect the MAF the car reverts to the Alpha-N map, which I believe estimates air volume instead using the engine speed and TPS. Do some Googling on it but IMO disconnecting the MAF doesn't prove anything conclusive as it doesn't really help you narrow down if a sensor is giving you an issue as the mapping has changed.

Have you tried INPA / DIS yet, see if you can run some tests and check for error codes. I fear your going to end up replacing a lot of expensive parts for no reason. For example, the ICV replacement is pointless, it really just works or doesn't it's a simple valve that opens and closes as you would have seen. Cleaning it is good but I wouldn't waste money replacing it.

It's safe to run without the MAF connected but absolutely no reason to do so long term unless you've specifically had Alpha N tuned for your modifications, such as running a CSL airbox where you have no MAF for example.

Oh, INPA would be useful for checking your long term trim's/adaptations, see if there's anything untoward there
An interesting option to maybe get an Alpha-N map tune. So do you know if the closed loop mode is running with the Alpha-N map, the same Alpha-N map as when the MAF sensor is disconnected?

I Have not yet tried INPA or DIS as I am still waiting on my cable to be delivered, but very keen to do so.
Well I wouldn't go the Alpha N route personally, unless you've got specific mods that require it and can take advantage, not a cheap route either. Alpha N doesn't adjust fuel trims to compensate for normal engine/sensor wear. It just runs best case scenario as its tuned to the optimal workings of the parts/engine whereas the base map will compensate for readings that variate from the factory defaults to achieve (I believe) lamba 1 or as close as. As a road car, the base map is fine but it does come with it's quirks, especially on for some reason our DME for the S54 which is slightly different to the M3 variation. I'm not sure anyone has worked out exactly why this is because the problem is fairly common as demonstrated on this thread. Alpha N still utilises the lamba sensors as normal as far as I am aware.
Sadly, trying to fix it can also be a money pit as there usually is no obvious reason, fault codes or otherwise. It could be many things related across the whole intake/fuelling chain.

All the sensors/working parts along this chain could be causing the issue, but probably the most important are:

VANOS
MAF
Lamba sensors
Air leaks/split pipes/cylinder issues (including head gasket)
TPS (including throttle pedal)
Throttle Actuator
Fuel system (including injectors/filter (which you can't replace)
Cam timing
CATS
Cam sensors

There's more but you'd hope you would get a error code for failures, though as mentioned, the base map will compensate for sensors not giving expected values within pre-programmed variations without giving error codes but potentially small issues with performance. As mentioned, the DME is looking to achieve lambda 1 and will adapt fuel trims across it programmed tables, long term and short to achieve this. If the lambda sensors (usually pre cat) are off, which is quite common on the S54 because of wear on these sensors then it messes up the whole chain to a degree so if you haven't already, deffo look at replacing the pre cat sensors.

After that, it becomes tricky. The VANOS controls the cam timing constantly (and as such the A/F ratio) and this in itself works by the readings from other sensors so it can be directly wrongly controlled by 'off' sensor readings or not adjusting correctly to correct sensor readings if its slightly faulty but not enough to give an error code. It's a proper minefield as one thing usually dictates another along the chain and our DME generally won't give error codes for these 'minor' faults as they aren't severe enough to warrant it with it's inbuilt 'ok' deviations.

Sorry if a lot of that doesn't actually help but hopefully it gives you a bit of an idea as to the confusing nature of the issue. If I was you, I would clean what you can which it sounds like you've done. Get the intake plenum off and clean the TB's, look for split hoses, ICV etc.
Then your looking at replacing parts, the obvious one's:

MAF
Lambda's
VANOS system
Check cam timing (can easily be disturbed and you want someone competent to check it/set it, will be done with any VANOS work so 2 birds with one stone)
Get it plugged in at BMW, there is a software update for our DME's and it may not have been updated. It was some time ago the update was released but mine only updated when I asked about it at BMW in 2016. It mostly addressed cold running issues but still worth doing.

After that, as you've already experienced, your into replacing parts which may or may not be fine, and on these engines, it's not a cheap venture, especially when you might be replacing parts which are perfectly fine.

It's a tricky one with no definitive answer sadly. Aim for the bigger/preventive parts that will benefit the resale value if you can otherwise you could be spending a lot of cash without benefit or perceived benefit when you come to sell. For example, a refurbished VANOS might help and it will also be a good thing for the future if you see what I mean as worthwhile preventative maintenance.

To add, when you get DIS working, do the VANOS test and see what the readings come back as. It will give a +/- 5 variations to factory defaults and if you are a fair bit outside these it could indicate a problem there, and wouldn't necessarily give an error code either.
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UPDATED::: Z4M S54 Engine Hesitation - POLL

Post by Buzzard88 » Wed Apr 10, 2019 3:50 am

AndyBeech wrote: Wed Apr 10, 2019 2:12 am
Well I wouldn't go the Alpha N route personally, unless you've got specific mods that require it and can take advantage, not a cheap route either.
Yes I agree and it would be just a bandaid.

Thanks for your detailed response, there's some good info there.

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UPDATED::: Z4M S54 Engine Hesitation - POLL

Post by ph001 » Wed Apr 10, 2019 8:49 pm

AndyBeech has put some great info up there, I perhaps would add to that the DME allows 20% long term fuel trim deviation before spitting out it’s dummy and pushing an error code. Thats a pretty big error imho.

Secondly, a lambda of 1 (ie perfect stoichiometric) is only good for one thing and that is emissions st steady state throttle and idle. For the car to make maximum torque and power, the mixture is way more rich than stoich. Hence any kind of serious throttle input is a mile away from a lambda of 1. That is why the o2 sensors are ignored during acceleration.
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UPDATED::: Z4M S54 Engine Hesitation - POLL

Post by BMWZ4MC » Thu Apr 11, 2019 2:07 pm

Buzzard88 wrote: Wed Apr 10, 2019 1:28 am
BMWZ4MC wrote: Tue Apr 09, 2019 2:22 pm
Buzzard88 wrote: Tue Apr 09, 2019 4:14 am After looking for the post cat sensors I couldn't even find the cats. Now I feel pretty stupid as Australian cars are the Euro spec which apparently don't have cats at the headers, they are way back underneath the car.
Where are you based in Aus?
Was in Newport until recently moving to Coal Point, Lake Macquarie. Nice to see a local.
Almost local - we’re in Neutral Bay. Let me know if you’re down in Sydney and feel like a drive.
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UPDATED::: Z4M S54 Engine Hesitation - POLL

Post by pwnsweet » Wed Apr 05, 2023 11:50 am

I'm raising the dead here, I know, but I read all 27 pages of this thread and I just had to make a post about my experience.

I had hesitation between 1500rpm and 3000rpm and the car would stutter when I went WOT between this rev range before giving me full power. Blipping the throttle at idle would result in misfire-like effects, where the throttle response felt delayed and there would be backfire-like sounds from the muffler.

I tried several suggestions from this thread, one at a time, until I isolated the issue to faulty Throttle Position Sensors. There are two:

1. One on the end of the throttle body assembly
2. One on the throttle actuator

They have 3 pins. You can measure if yours are bad by using a multimeter and setting it to Ohms. Put one probe on pin 1 and the other on pin 2. Rotate the sensor and the Ohm value should range between 1000 ohm and 4000 Ohm. If the upper number is larger than 4500 ohm, your TPS is going bad and should be replaced. This rule only applies to TPS with part numbers 13637840383 and 13631402143. I hope this helps someone from the future.

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UPDATED::: Z4M S54 Engine Hesitation - POLL

Post by Simon 3.2M » Wed Apr 05, 2023 1:02 pm

To add my 2 penneth worth, my roadster dipped when the clutch was depressed and it had the usual hesitation. I carried out my usual regular servicing and changed the oil and plugs - the cars pulls more strongly and the revs no longer dip. Maybe there is a correlation, I don't know but it may assist.
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UPDATED::: Z4M S54 Engine Hesitation - POLL

Post by Vanne » Thu Apr 06, 2023 2:34 pm

just thought I'd add some observations. maybe worthwhile, maybe rubbish. either way...

the S54 is EXTREMELY sensitive to back pressure.. while i was developing my car, i ran it for quite some time ending at the Xpipe (no pipes backwards from the xpipe). now you also have to know that i have no cats and straight through X pipe from Supersprint, as well as the Section 1 from supersprint.. , along with stepped headers from the same mob. Either way, so theres no back pressure.. and that revved like it was going outa fashion.. also other mods, but we wont go into that here..

When it came time for me to get the rear section put on, (3 inch going into 4 inch), and i was away while the guys at the garage welded up the rear pipes, (which are also empty), though they welded up the cans with 2 90 degree bends in it.. At the time i commented on that that would produce too much back pressure, but the guy assured me it would not!! yeah right.. This DID produce a certain amount of loud pedal lag due to a lot of back presusure.. I drove it like that for a few laps.. pulled in and at that point decided to get them to re-weld the rear 3 inch to 4 inch section (i have pics somewhere) section, with only 1 flowing bend in it.. A world of difference.. revs so freely now, like it did with no rear exhaust on it at all.

This was from idle to wot.. sometimes to the point where the car would nearly stall.. absolutely zero issues now.. revs like a MF.. :evil:

so adding to that list you might wanna see if the exhaust system has been modified. :roll:

just my 2 dirhams. :thumbsup:
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UPDATED::: Z4M S54 Engine Hesitation - POLL

Post by Slideways » Fri Apr 07, 2023 12:01 pm

Simon 3.2M wrote: Wed Apr 05, 2023 1:02 pm To add my 2 penneth worth, my roadster dipped when the clutch was depressed and it had the usual hesitation. I carried out my usual regular servicing and changed the oil and plugs - the cars pulls more strongly and the revs no longer dip. Maybe there is a correlation, I don't know but it may assist.
Idle dip when coming to a stop can be caused by a vacuum leak somewhere in the intake system or a faulty MAF. If you serviced the intake system and tightened up the clamps in and around the MAF, then that would resolve the issue.

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UPDATED::: Z4M S54 Engine Hesitation - POLL

Post by Simon 3.2M » Thu Jul 13, 2023 8:57 am

A further update - it’s back somewhat on mine now however, if I engage the sport button the car drives perfectly and you can “stab” the throttle without issue etc.
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UPDATED::: Z4M S54 Engine Hesitation - POLL

Post by PDJ » Thu Jul 13, 2023 1:39 pm

Simon 3.2M wrote: Thu Jul 13, 2023 8:57 am A further update - it’s back somewhat on mine now however, if I engage the sport button the car drives perfectly and you can “stab” the throttle without issue etc.
The sport button just adds 20% to the position it is actually in, so my suggestion would be one of the two throttle position sensors

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UPDATED::: Z4M S54 Engine Hesitation - POLL

Post by Slideways » Sat Jul 22, 2023 6:23 am

Don't forget the throttle pedal. That also can cause throttle position issues. The TPS at the front of the engine is usually the first to try as it is easy to access. The TPS sensors can be tested with a multimeter if you want to try that route.

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