Hesitation on slight throttle - now with video

On the subject of Tesco Momentum - i also try to avoid it as my car seems to lose some of it's smoothness through the revs. I also get slightly lower mpg.

I stick to Shell/Waitrose (BP) as it's cheaper anyway - Momentum is 4p more round here
 
My car runs like a beast on Momentum, smoothness isn't really what I'm looking for in this car. There's are two studies that I know of on this, one in Evo magazine and the other by Thorney Motorsport. Both conclude that Momentum/99 gave the best power returns in it's category. I accept that Thorney has a sponsorship tie in with Tesco but they're well respected and provide the stats to back up their claim.

It's Vpower that I'm not particularly keen on, it makes my car far too unpredictable on the throttle and the quality of it seems to vary from tank to tank. Anyway as long as no one has any proof to back up claims that Momentum may be of inferior quality then I'll continue using it. In fact I drive out of my way to get it, there's a Shell garage around the corner from me.
 
mmm-five said:
, so maybe it's something to do with the throttle potentiometer/setting?
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You know, this is more my thought. Mine is as the video, but after resetting the adaptive throttle it seemed better/different.
 
dgm said:
My car runs like a beast on Momentum, smoothness isn't really what I'm looking for in this car. There's are two studies that I know of on this, one in Evo magazine and the other by Thorney Motorsport. Both conclude that Momentum/99 gave the best power returns in it's category. I accept that Thorney has a sponsorship tie in with Tesco but they're well respected and provide the stats to back up their claim.

It's Vpower that I'm not particularly keen on, it makes my car far too unpredictable on the throttle and the quality of it seems to vary from tank to tank. Anyway as long as no one has any proof to back up claims that Momentum may be of inferior quality then I'll continue using it. In fact I drive out of my way to get it, there's a Shell garage around the corner from me.
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Really strange. I wonder if Momentum varies regionally? My arse-dyno would put it somewhere between 95 and VPower/BP in terms of power (especially over 5,000rpm). Since the cars are the same, it must be the fuel that varies.

I've read the Thorney article several times before - it's an old one. The "recipe" for all the fuels concerned will have changed a few times since then.
 
Just to say, what I've been told about fuels doesn't come from dyno runs on cars by tuning companies or anything. This was based on base analysis (spectrum analysis I think, gives a split of everything that is in the oil/fuel, from the different spikes on the graph can tell what it consists of, was shown it briefly) of samples of all the fuels and oils. Then selected fuels were run on the same type of engine over 100k on an engine dyno, with regular oil samples, these were processed to see what kind of oil degradation had occurred, and to see what parts of the fuel had got into the oil. At the end of the 100k the engines were stripped and inspected for differences internally, as well as parts such as the fuel lines and pumps inspected.

Aim of the original project was to look at the effect of oil degradation when using high sulphur diesel (a lot more oil dilution due to regens in diesels, not something anyone with a Z4 has to worry about thankfully), but the project ended up with a much broader scope when every realised there were so many different fuel variations out there. No-one wanted to get caught out but one of the fuels causing something funny to happen....

This was 12 months or so ago, I do not keep up on what Tesco Momentum (or any other fuel) changes are made, and it could well vary regionally due to the different refineries local to each area.
 
raiets said:
[youtube]m2YaQZHILR8[/youtube]

Be really interested to know how others get on :driving:
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Well, it looks like you borrowed my car for the video... :D ... well, not really :D but rather :( at the time.
 
Shooter said:
raiets said:
Be really interested to know how others get on :driving:
Click to expand...

Well, it looks like you borrowed my car for the video... :D ... well, not really :D but rather :( at the time.
Click to expand...

Sort of glad I'm not the only one, but its also :( I'm still trying to find time to get the oxygen sensors changed out and will report back as soon as I do! :thumbsup:
 
I test drove a 2007 Z4cm with 45k kms on it yesterday that had this exact problem. Very frustrating when blipping on downshift as other have mentioned. Incredible car otherwise
 
i had this but drive it normally and all seems fine , when you stab the throttle it plays up, ...... dont stab the throttle, :driving:
 
I used to do that but until you change the fluffed sensors you don't appreciate how crisp the throttle is on the s54 :)


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i get the throttle dip but don't think I get hesitation. I have stalled around 3 times in the last year, always when pulling away slow in a car park then having to brake with foot also on clutch. So it has stalled while foot is firmly on clutch
 
Finally got around to change both actuator sensors, the hesitation is gone ! :thumbsup: :thumbsup: :thumbsup:

Quick pic of the engine during the process :
shooter_1356949651_papillons.jpg

It was easier than i thought, quicker too. The biggest problem is removing the clamps on the air collector. I destroyed two in the process before figuring it right, but i had bought spares just in case.
While at it, i also noticed that the rubber grommet at the entrance of the air box was misaligned, it was seated partly on the exterior of the air box (correct) and partly inside (not correct at all). My guess is that it was misaligned at the factory.
I also wanted to clean my idle valve actuator, but since i didn't have spare clamps, i didn't do it. I'll do this next time (when i get around to buy a carbon air collector :D ).

BTW, idle dip is still there...
 
Has anyone who suffers from idle dip tried having their injectors cleaned? I think that may have been what fixed it on mine, or at least improved it to a great deal.
 
I tried some fuel system cleaner on mine, BG44K to be exact and it made no difference.

Car is booked in for next week for BMW to check/change the sensors which will hopefully fix it.
 
Not sure if they are easy to check - my dealer tried three times to diagnose the problem and changed the air flow meter instead :-/ apparently it was "backfiring into the intake" when they looked the third and final time. Lost credibility at that point tbh.

That said the air meter was probably goosed too as the mpg improved 10-20% after that was changed.


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I believe you can check them with a multi meter through their range, that's what they are hopefully going to do.

I'm fairly sure it's something to do with the throttle position on my car though so it's either them two sensors or the pedal it's self.

It's like the 0%-5% throttle operation has gone completely, results in a massive jerk each time your crawling in traffic and try to apply the throttle smoothly, apart from being massively annoying it can't be doing any good to the drivetrain the knock/bang when it shunts isn't a nice at all.
 
I tried with a multimeter vs the new one, difficult to say if it gave any different readings. Would probably need to sweep it full range with an oscilloscope to find the abnormality. The old switch did spin rather loosely.


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Hi everyone. I'll post my experience here too, Have a 57 plate Z4M, done 25,000 miles in it taking it to 35,000 miles. The hesitation is indeed irritating. Doesn't do it on sport mode, but that setting is too manic for me. The splutter is everything people say here, and I generally go careful on roundabout take-offs in any gear. Stalls in reverse sometimes, but never stalls in forward gears. I found it pretty much went away for about 3,000 miles with new plugs, but could have been the throttle reset. I've never been able to get any improvement from resetting the adaptive throttle but may not have been doing right. Petrol makes no difference, all types and even 95 the same. Notice no difference in different weathers. A few times it caused a misfire type effect slowing in third and taking off again, transmission bang. Had 2 stroke motorcycles with mich better throttle response from idle, expected better from this car. Get some relief after thrashing it for 40 miles or so, very fast, then all seems to tighen up and hum, until 10 miles of urban driving then back to its ways. Good luck everyone!
Tony
 
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