BMW Z4M S54 - slight hesitation/stutter when you press the accelerator from idle.

Thanks all for responses.
It’s making me feel better as a very common ‘quirk’ it seems and it doesn’t effect my driving too much - just annoying..

Interestingly i would like to fit a csl style airbox with a map.
Are we saying this doesn’t seem persist if this is done? 🤔
 
AndyBeech said:
Cheers Tom, appreciate it, I'll bear it in mind for the future but not too motivated to fiddle with bits at the moment as it all works well enough that it doesn't bother me at the moment.
It was worse when I bought the car interestingly, revs sometimes dipped enough it would stall which was a lot more annoying. Don't know what was replaced to stop it doing that, possibly the ICV, but hasn't done that for years thankfully, just a few hundred rpm dip these days at worse.



How'd you know it was out of spec out of interest? Thought knock sensor's either work or they don't?
Click to expand...
Resistance values on the knock sensors.

New ones all very close, 2x old ones say 20% away, 1 by the bulkhead 100% away.

I data logged before and after, it was pulling timing which I had confirmed on the Dyno.
 
RedUn said:
Resistance values on the knock sensors.

New ones all very close, 2x old ones say 20% away, 1 by the bulkhead 100% away.

I data logged before and after, it was pulling timing which I had confirmed on the Dyno.
Click to expand...

Interesting… what software did you use for data logging? I’ve got an app which reads via OBD so can get timing iirc, but I can’t recall seeing anything for the knock sensor values. How did you test the resistance of them? I assume you used the new ones as a reference reading, do you remember what that was?

Might have to dig it out and have a look at the timing on a pull as I’ve had it bog under full throttle a couple of times and heel/toe can be a bit hit and miss at lower revs despite not the engine TPS being replaced (no difference)
 
Last edited:
RedUn said:
Resistance values on the knock sensors.

New ones all very close, 2x old ones say 20% away, 1 by the bulkhead 100% away.

I data logged before and after, it was pulling timing which I had confirmed on the Dyno.
Click to expand...
Where did you get your dyno'd?

Interestingly when Martyn was mapping mine back when I had the eventuri & sports cats, he said he was seeing knock and it was pulling timing. He's said it's been much happier on the airbox, but I had always meant to do the knock sensors but never got round to it...!
 
RedUn said:
Resistance values on the knock sensors.

New ones all very close, 2x old ones say 20% away, 1 by the bulkhead 100% away.

I data logged before and after, it was pulling timing which I had confirmed on the Dyno.
Click to expand...
I didn't think testing knock sensors for resistance is really a thing?
Resistance changes cannot tell you if the sensor is actually generating a voltage when the engine knocks.
Pelican suggests testing s54 knock sensors with a volt meter at the dme pin outs...
"Testing knock sensors: To test the sensors, you will have to access the DME electrical connector. See our tech article on DME replacing. Working at the electrical connector, you will backprobe the connector with the ignition ON. There are four wires at the connector, two for each sensor. One is a ground, the other is a reference voltage used for circuit integrity. To test the bank 1 knock sensor, backprobe Pin 29 at the DME, yellow wire. To test the bank 2 knock sensor, backprobe pin 31 at the DME, green wire. Double-check the wiring for your vehicle. This is what it was for my subject vehicle. Here's the quick test. Use a DVOM. Connect the black lead to battery negative. Then connect the positive lead to the sensor wires. One wire should read close to 0 volts, this is the sensor ground. The reference voltage wire should read around 2.5 volts, for a good sensor. A bad sensor will either short the reference voltage to ground, or not pull it down to 2.5, therefore giving a reading of about 5 volts. "
 
Adamw said:
Interestingly i would like to fit a csl style airbox with a map.
Are we saying this doesn’t seem persist if this is done? 🤔
Click to expand...
That's what I would like to know! But even if everyone who has one chimes in to say they don't have this problem the sample set would be small enough that drawing any real conclusions would be a folly. There's what, 5-10 of us on here with one, I don't think more.
 
beanie said:
Might have to dig it out and have a look at the timing on a pull as I’ve had it bog under full throttle a couple of times and heel/toe can be a bit hit and miss at lower revs despite not the engine TPS being replaced (no difference)
Click to expand...
Not wanting to open that can of worms again:popcorn:but was the map done by evolve/eventuri/imran whoever you want to call them?:)
When I had their map on my m3 wide open throttle inputs (if I remember right) in 3rd gear would cause the engine to bog/stutter, I'm not quite sure how to describe it but it was very annoying.
 
TomK said:
That's what I would like to know! But even if everyone who has one chimes in to say they don't have this problem the sample set would be small enough that drawing any real conclusions would be a folly. There's what, 5-10 of us on here with one, I don't think more.
Click to expand...

Sorry forgot to reply, mines still the same. And head gasket been replaced recently with all associated new seals etc. and still the same.
I’ll email Josh (tuner) and see if he knows anything about it though don’t know if they have the issue across the pond.
 
TomK said:
Not wanting to open that can of worms again:popcorn:but was the map done by evolve/eventuri/imran whoever you want to call them?:)
When I had their map on my m3 wide open throttle inputs (if I remember right) in 3rd gear would cause the engine to bog/stutter, I'm not quite sure how to describe it but it was very annoying.
Click to expand...

😅 no the map was done at Regal in Southampton (I think you might have pointed me in their direction?) as back then the Evolve map wasn’t any good- didn’t allow for heel/toe and some suggested it was a tweaked limp mode map.

The bogging is very very rare and not something that bothers me enough to dig very deep on. Funnily enough I think it’s also mostly in 3rd, can’t think at what Revs but it’s never extremely low nor high. For context, it also happened a couple of times before the airbox/map and prompted me to change the tps. The seemingly inconsistent blipping on downshifts has also always been a thing at lower revs. Get it singing though and it’s nice and crisp.
 
beanie said:
Interesting… what software did you use for data logging? I’ve got an app which reads via OBD so can get timing iirc, but I can’t recall seeing anything for the knock sensor values. How did you test the resistance of them? I assume you used the new ones as a reference reading, do you remember what that was?

Might have to dig it out and have a look at the timing on a pull as I’ve had it bog under full throttle a couple of times and heel/toe can be a bit hit and miss at lower revs despite not the engine TPS being replaced (no difference)
Click to expand...
I was logging the timing values and fuelling not the knock values I couldn't find those either on the torque pro app or whatever it's called these days.

I can't remember the readings now although I do still have the old knock sensors I can dig out and meter if you wish?

Ultimately you could tell quite easily that once changed no timing pull so data logged or not, there was no dip in power like there was previously.

I do think I am fairly close to maxing the injectors though so that's my next mission once I get around to it!
 
RedUn said:
I can't remember the readings now although I do still have the old knock sensors I can dig out and meter if you wish?
Click to expand...

Thanks for the offer, but there’s no need to trouble yourself. Seeing as it’s not a big issue for me and I have little to no space to work on the car, it’ll be a while before I get to it.
 
Ed Doe said:
Where did you get your dyno'd?

Interestingly when Martyn was mapping mine back when I had the eventuri & sports cats, he said he was seeing knock and it was pulling timing. He's said it's been much happier on the airbox, but I had always meant to do the knock sensors but never got round to it...!
Click to expand...
TRS did my tune, they seem to work with Martyn also.

What rpm did you get timing pull? Mine was 7k ish
 
TomK said:
I didn't think testing knock sensors for resistance is really a thing?
Resistance changes cannot tell you if the sensor is actually generating a voltage when the engine knocks.
Pelican suggests testing s54 knock sensors with a volt meter at the dme pin outs...
"Testing knock sensors: To test the sensors, you will have to access the DME electrical connector. See our tech article on DME replacing. Working at the electrical connector, you will backprobe the connector with the ignition ON. There are four wires at the connector, two for each sensor. One is a ground, the other is a reference voltage used for circuit integrity. To test the bank 1 knock sensor, backprobe Pin 29 at the DME, yellow wire. To test the bank 2 knock sensor, backprobe pin 31 at the DME, green wire. Double-check the wiring for your vehicle. This is what it was for my subject vehicle. Here's the quick test. Use a DVOM. Connect the black lead to battery negative. Then connect the positive lead to the sensor wires. One wire should read close to 0 volts, this is the sensor ground. The reference voltage wire should read around 2.5 volts, for a good sensor. A bad sensor will either short the reference voltage to ground, or not pull it down to 2.5, therefore giving a reading of about 5 volts. "
Click to expand...
Yeah I saw that at the time but the connectors are sealed...hence no back probing. I choose to check the new and old resistance wise just for reference. Like I said the one by the bulkhead was definitely different to the others, it was clearly still working as I had no EMLs but I'd say on its way out?

Once new ones fitted, problem disappeared and that was the only thing I changed at the time so it had to have been those?
 
You must log in or register to reply here.
Back
Top Bottom