Hesitation on slight throttle - now with video
- Thread starter M@r]{
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The guys at the Indy said its not right i think it may just be the clip then mark as like is aid im not seeing anything wrong.... if i plant my revs they shoot up instantly, i also get no rev droop at all my but idle and other values are set very differently to yours..... if look at doing a maf swap, if you want your more than welcome to pop dpwn to mine where we can fit mine and see if this helps, this way it stops you having to fork out 200 plus for a new genuine maf??? would this help??
pilchardthecat
Active member
so i tried it out, and i do get a dip when the revs drop back.
i think this is due to the hand-over from the throttles (which close) and the idle air actuator/inlet which provides the air for the engine at idle and very low loads
i think this is due to the hand-over from the throttles (which close) and the idle air actuator/inlet which provides the air for the engine at idle and very low loads
I'm in the same boat as most it seems. I have tried Shell V-Power, BP Ultimate, Total Premium and Tesco Momentum, none seem to make a difference to this issue, but it didn't like the Tesco Momentum stuff when starting so in my experience would steer away from that (but it's so cheap 
).
Video of mine, the dips seem a little bigger than the OP's, when hitting 500rpm the lights in the car dip a little, that's how close it is to stalling. Drivers door is open and I'm in a garage so you can hear the "pop" or "misfire" sound when I tip in. I'm really pressing the throttle down far and quickly, quite an aggressive tip in. If I just roll on to the throttle a bit slower there are no "pop" sounds and the engine picks up cleanly.
[youtube]m2YaQZHILR8[/youtube]
My ideas so far much along the lines of most, ECU clearly doesn't know how much fuel or air is going through the engine at the time, so MAF or front lambda sensors. Would start with the lambda sensors (I will get round to this myself when I get some time...).
As for the M3 not suffering with this, I think I read somewhere that the Z4M uses a different ECU, something more closely related to the V8 M3 and the V10 M5. This means they would have carried over the calibration as much as possible, but there will be some significant differences I'd imagine. **EDIT** Bit of reading and can confirm the S54 in the Z4M uses the MSS70 ECU and the MSS45 ECU is used in the E46, could explain some difference at least.
Also, don't know if this is only in my head, but it seems to be worse when it has been raining (which is always in the UK :| ), so it might be something to do with the humidity correction in the calibration not quite being right for the Z4 induction system.
Be really interested to know how others get on
).Video of mine, the dips seem a little bigger than the OP's, when hitting 500rpm the lights in the car dip a little, that's how close it is to stalling. Drivers door is open and I'm in a garage so you can hear the "pop" or "misfire" sound when I tip in. I'm really pressing the throttle down far and quickly, quite an aggressive tip in. If I just roll on to the throttle a bit slower there are no "pop" sounds and the engine picks up cleanly.
[youtube]m2YaQZHILR8[/youtube]
My ideas so far much along the lines of most, ECU clearly doesn't know how much fuel or air is going through the engine at the time, so MAF or front lambda sensors. Would start with the lambda sensors (I will get round to this myself when I get some time...).
As for the M3 not suffering with this, I think I read somewhere that the Z4M uses a different ECU, something more closely related to the V8 M3 and the V10 M5. This means they would have carried over the calibration as much as possible, but there will be some significant differences I'd imagine. **EDIT** Bit of reading and can confirm the S54 in the Z4M uses the MSS70 ECU and the MSS45 ECU is used in the E46, could explain some difference at least.
Also, don't know if this is only in my head, but it seems to be worse when it has been raining (which is always in the UK :| ), so it might be something to do with the humidity correction in the calibration not quite being right for the Z4 induction system.
Be really interested to know how others get on
raiets said:Also, don't know if this is only in my head, but it seems to be worse when it has been raining (which is always in the UK :| ), so it might be something to do with the humidity correction in the calibration not quite being right for the Z4 induction system.
Be really interested to know how others get on
As I said in one of the other threads on this subject, on the rare occasion when mine has stalled it has been when stuck in traffic in the rain... I think that some of this is just the way the car is (as expressed by those of us who don't really have much of a problem) whilst some people really do have something up with their car that is an exaggerated form of this engine characteristic. My first suspicion would be with the lambda sensors as my old TT had a failing lambda sensor and could run rough or well depending on the day/weather/it's mood... The lambda sensor was not reliably returning the expected voltage when interrogated by a garage PC, but worked well enough for the check engine light not to illuminate.
ga41 said:
I have read your posts, they have been really helpful, its just having time to doing anything about it at the moment
O2 sensors are first on the list, really hoping these make an improvement, as replacing the MAF and getting the injectors flow balanced are both rather costly raiets said:I'm in the same boat as most it seems. I have tried Shell V-Power, BP Ultimate, Total Premium and Tesco Momentum, none seem to make a difference to this issue, but it didn't like the Tesco Momentum stuff when starting so in my experience would steer away from that (but it's so cheap
I don't get the perception that that Tesco Momentum is in some way inferior to the other higher octane fuels. I've used it in my car on it for years and it runs magnificently on it. The reputation that supermarket fuels developed in the 90's isn't going to die easily it seems.
dgm said:raiets said:I'm in the same boat as most it seems. I have tried Shell V-Power, BP Ultimate, Total Premium and Tesco Momentum, none seem to make a difference to this issue, but it didn't like the Tesco Momentum stuff when starting so in my experience would steer away from that (but it's so cheap
I don't get the perception that that Tesco Momentum is in some way inferior to the other higher octane fuels. I've used it in my car on it for years and it runs magnificently on it. The reputation that supermarket fuels developed in the 90's isn't going to die easily it seems.
This isn't me being stuck up about fuel
I want to be able to put tesco momentum in as its only 140p a litre, but when running on it the engine needed 2 sometimes 3 more revolutions on the starter before it fired. The instant I run it on BP Ultimate it was back to starting in the normal amount of time. Other than that I noticed no difference.I have worked with people who do research for big OEM's on fuels, and we have talked at length about different fuels, not just in the UK but across the world. I would say I know the real differences between them, but its probably better to say I know the results of their research. I don't want to go on about ethanol levels, or detergents, or whatever, just put what you want in, and then use it far too quickly in my case
If your associates have anything negative to say about Tesco Momentum then I for one would like to hear about it as I don't want to use an inferior product in terms of performance or composition of the fuel. What I would say is that I've tried all sorts of fuel in the car over 5 years in Britain and in Europe and genuinely find that it runs best on Momentum. It's not the price that dictates what I'm using, if there's a better alternative that costs a bit more then that's what I'll use.
I don't really want to go into it all, but unless you're doing loads of miles (100k year sort of thing), or live in extreme temperatures (I'm sure being relatively far north you know the importance and difference between summer and winter fuel just in the UK), or the car is being used to its maximum at all times, then the differences between the fuels will make no real difference to component wear or life. If your car is running fine, then I wouldn't worry.
My slower starts on Tesco Momentum might be related to this idle issue, or just something to do with my cars fuel learnings. I was running BP U, then tried Tesco M, about 1/3 of the way through the tank I started noticing the slower starts, tried another tank and they remained. Switched back to BP U, slower starts improved through the first half of the tank, next tank didn't notice anything, back to normal. Filled with Tesco M last weekend, I am about half way through this tank and the slower starts are definitely back. Will run this tank down and try BP U again.
My slower starts on Tesco Momentum might be related to this idle issue, or just something to do with my cars fuel learnings. I was running BP U, then tried Tesco M, about 1/3 of the way through the tank I started noticing the slower starts, tried another tank and they remained. Switched back to BP U, slower starts improved through the first half of the tank, next tank didn't notice anything, back to normal. Filled with Tesco M last weekend, I am about half way through this tank and the slower starts are definitely back. Will run this tank down and try BP U again.
From what I've been told, yes, some of the chemicals used are not as 'good' as the additives in other fuels, but I couldn't tell you what the difference was or why they aren't deemed as good. They also said tesco m relies a lot on ethanol to boost the octane, which it's not uncommon, but ethanol is quite abrasive stuff, older engines wouldn't have been tested or developed with higher percentage ethanol in mind. Like I said though, these differences wouldn't show over small mileages, so I wouldn't worry.
Liverpool
Here's mine for comparison.
First one was as soon as I switched the engine on from cold...
[youtube]aIR89g288jM[/youtube]
Second is from about 5 minutes later when it's warmed up a little...
[youtube]3_-uQOl5dVQ[/youtube]
See a 100 or so RPM drop in the 2nd video, and an occasional rough pick-up, but only in 'normal' mode. Once I put it in 'sport' mode there was no initial pick-up roughness, so maybe it's something to do with the throttle potentiometer/setting?
First one was as soon as I switched the engine on from cold...
[youtube]aIR89g288jM[/youtube]
Second is from about 5 minutes later when it's warmed up a little...
[youtube]3_-uQOl5dVQ[/youtube]
See a 100 or so RPM drop in the 2nd video, and an occasional rough pick-up, but only in 'normal' mode. Once I put it in 'sport' mode there was no initial pick-up roughness, so maybe it's something to do with the throttle potentiometer/setting?
Thanks for the comparison videos, its really helping to see what other people are experiencing 
To add further details to mine, I recorded that on a particularly bad 'day', no idea what made it worse that day, but it was. Some days it will be exactly as mmm-five's video show, with barely 100rpm dropped and only a little hesitation on tip-in. In both of mmm-five's video's the idle still seems a little high because the engine is cold, to me. When cold (first 5 minutes or so) mine is perfect, no hesitation on tip in, no idle undershoot. Its only once fully warmed through and the idle set speed is at it's lowest do the 'problems' start appearing.
This I think is also another finger in the direction of the lambda sensors. Don't think these are relied upon as much in warm up as the calibration is probably desperately trying to heat the CAT up as quick as possible, throwing in fuel everywhere to get it lit
silly emissions cycles 
Interesting that my idle seems a little low, I don't see any reason it would change between vehicles or even model years. Anyone know if INPA or any of the other tools can change the idle speed??
I have finished my tank of Tesco M now, unfortunately was nowhere near a BP station so ended up with Shell V-Power I will see how this weeks starts go. Although we are apparently due some rather nice weather this week, which will not make for a fair comparison. Not going to complain about some nice weather though (doubt you tent tops will either!)
To add further details to mine, I recorded that on a particularly bad 'day', no idea what made it worse that day, but it was. Some days it will be exactly as mmm-five's video show, with barely 100rpm dropped and only a little hesitation on tip-in. In both of mmm-five's video's the idle still seems a little high because the engine is cold, to me. When cold (first 5 minutes or so) mine is perfect, no hesitation on tip in, no idle undershoot. Its only once fully warmed through and the idle set speed is at it's lowest do the 'problems' start appearing.
This I think is also another finger in the direction of the lambda sensors. Don't think these are relied upon as much in warm up as the calibration is probably desperately trying to heat the CAT up as quick as possible, throwing in fuel everywhere to get it lit
silly emissions cycles Interesting that my idle seems a little low, I don't see any reason it would change between vehicles or even model years. Anyone know if INPA or any of the other tools can change the idle speed??
I have finished my tank of Tesco M now, unfortunately was nowhere near a BP station so ended up with Shell V-Power I will see how this weeks starts go. Although we are apparently due some rather nice weather this week, which will not make for a fair comparison. Not going to complain about some nice weather though (doubt you tent tops will either!)