My 12 reg Merc stop/start has stopped stopping when the car stops
Does anyone know reasons for this and how I get it to start stopping again?
Cheers
TAG
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If it's anything like my BMW M3, there are a whole host of factors that the car takes into account before stopping the engine - including state of battery charge, engine and ambient temperature, whether the air con is on, etc, etc.
Most likely is that your battery is not sufficiently charged - or that you have switched the Stop/Start system off :-)
Mine did this when the battery was getting towards the end of it's useful life.
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I can't help with the problem but I think your thread title is superb.
My Merc is the same. I’m not bothered by it though because it’s a taxi. You can imagine how many times a day it would have gone through the stop/start cycle.
Probably battery given it’s a bit colder and journeys in dark with electrics fully on.
Jim
As others have said there are a host of factors that affect the start stop system. I run a Volvo and a VW and at this time of the year they often don’t stop every time. Lots of factors like heated windscreen in use, ambient temperature, aircon, etc plus taking longer to warm up etc. It’ll return to normal I’m sure
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My BMW did this when the air con leaked & I needed a new condenser.
...meaning the air con pump was ‘always on’ so it kept the engine running to power it.
Air con fixed & it’s back to normal.
Might be worth a check.
z
Assuming that you didn’t gave the aircon on, battery
If I recall right Kia needed 85% battery charge and a low demand from the alternator to enable the stop/start, air con on pretty much rules out the s/s working.
And when tbe battery is changed it needs plugging in and the battery monitor needs resetting too.
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I’ve turned mine off, it supposed to be not that good for the turbos especially after a long high speed drive.
Couldn't stop myselfOriginally Posted by AlphaOmega
Air con on/off used to make a difference
How does one check the quality of a car battery?
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When mine was working I would always press to button to prevent it switching off when leaving the motorway after a long run for just this reason.
quite a few reasons to turn stop/start off - but I suppose it depends on how long you keep the car and how old it is
https://www.autocar.co.uk/car-news/n...r-car-s-engine
I paid for the dealer to set my car to have start /stop default as “off” when the car starts, I took my wife’s car to have it done too a few weeks later but the dealer said some new EU legislation stopped them doing it. Hate start stop.
Bought a dongle and used the app to set mine to remember last setting.
So now permanently off...
It’s fairly unlikely that you would be making lots of boost and then stopping straight away on the road, it is better to let the car idle for a few minutes before turning off, but how many people do that.
Can’t help with the original question but I disabled Auto Stop/Start in the software on my Audi some years ago. More accurately I set the default setting to OFF. I rarely drive in city centres and it’s a complete pain in everyday use. A car at idle uses a minuscule amount of fuel but the additional wear and tear on starter motors, batteries etc. is significant. In a choked city centre e.g London I can understand it but outside of this it gives the car owner no benefit.
Off permanently is best.
Shutting it off on most VAG products is easy. Simply a plug-and-play from a computer with the codes. Lots of indy workshop have that facility. And it won't cost and arm and a leg. Search for 'VAG codings' or similar.
BMW has the possibility to have it shut off as well. And when 'Europe' demands it should be 'on', there's a big chance that the dealer will not cooperate. Go to an indy.
My Audi did the same thing,a new battery sorted it out.
+1!
Mine doesn’t seem to be working and I couldn’t be happier stop start is the most annoying thing ever
Its a naff piece of tech that does nothing for health of car whatsoever and causes us issues in workshops
Essentially manufacturers came up with it to dodge / trick emissions effectively meaning that when calculating emissions they deducted hypothetical ‘stand by’ times from journeys thus reducing published outputs.....
ECU takes in many factors as said a big one being battery condition so if you have done short trips it might not function if the battery is at End of life it might not function.
Go on long run with it off then see if it starts working again....alternatively turn it off forever...
The only time i ever felt the need to turn a car off was stuck in mega tailbacks on motorway or sat waiting for someone ......at junctions or lights ..errrr NO.
But that is exactly what happens if you have just done a big journey on a motorway and then come to a stop at a roundabout after exiting the motorway.
My Golf R has it, switching to sport mode takes a pull on the DSG selector & switches start/stop off, it makes the car go faster too :-)
My Golf has done the same as it does every time this time of year, it’s the cold weather that has an impact on the battery. Nothing to worry about. As others have said, there are various factors that prevent stop and start and a cold battery/engine is one of them.
My old golf dsg used to have it and if you tried to make a quick getaway at the lights it used to lurch forward I disabled it by disconnecting a plug on the battery
This is true.
Additionally I'll back up the other comments here, something within the system will be sending status codes to the ECM which is determining that its not ideal conditions to Stop/Start.
Battery getting to end of life is indeed prime candidate, but could also be something as simple as a dirty sensor or inefficient ancillary e.g. the AC.
Do you have a local friendly independent with the STAR system, it may have logged some "invisible" status codes which will tell you.
Ta,
The Turbo development Engineer
I turn mine off all the while, for the above and BMW engine cam chains are susceptible over time
The main issue is heat soak, so anything under heavy load followed by a stop is less than ideal.
Obviously the systems are developed to cope with everything you're likely to through at it, but quality variation, how you & previous owners have used it, etc... all play a part.
FWIW, my 16 plate Merc did the same thing for a while. It was down to the auxiliary battery failing. AIUI the auxiliary battery is the one that runs all the services (air con, radio, etc etc) when the car is stopped. I'm not sure whether the aux also starts the engine when stop/start is enabled. Anyhow, the auxiliary battery was replaced. The main battery was and is fine.
I did get a series of battery warning messages on the dash when all this was going on.
We've had cars without all this tech so just revert back to normal!.
@ A turn it on
@ B turn it off
Genuine question, why do people feel the need to turn this function off? - is it because I’ve only ever driven geared cars not automatics? (My wife hates automatics and we live in the country so we don’t get stuck in traffic very often). In my cars you need to stop the car, apply the handbrake and put the gearstick into neutral - and the engine instantly fires to life the second you depress the clutch to pull away. How does it vary with an automatic box? - the last auto I had was an ancient Volvo V70 that preceded this system
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I think that the main (generalised) reasons are as follows
1). Additional wear on the Starter Motor - although "software" is now supposed to stop the car at TDC - i.e. less strain on Starter Motor
2). Additional wear on the Battery
3). (less) but additional wear on certain engine components - Rod Bearings, Turbo etc.
4). Another "complication" to go wrong and expensive to put right
I think the figures are 10 x the use of Battery and starter motor versus non start stop
Manufacturers are improving lubrication all the time so 3). may not be as relevant
Additional "petrol cost" saving is difficult to estimate - but some say it is £100 over a 12,000 mile period - but again that depends on lots of factors, and individual journeys and driving styles
Last edited by BillN; 6th November 2019 at 15:23.
With an auto it is usually when you take your foot off the brake.
I guess people who turn off the stop/start function hate the whole idea as constantly stop/starting an engine puts much more strain on the components.
From what I have read engines and electrics have been up rated to hopefully deal with the extra load on components but from an engineering POV stop/starting makes no sense at all.
Cheers,
Neil.
as I said in my 2015 1.4 petrol golf dsg auto golf if you wanted to pull out quickly from a roundabout say it would nearly chuck you through the windscreen if the stop start was on, also my workmate just bought a 35000 mile skoda citigo and the starter motor went 2 weeks later the aa bloke said he was seeing more and more starter motors and batteries going on relatively new cars with stop start
Had two cars with stop/start tech. Both of them never worked very well.
As above,lots of reasons why. I have stopped myself thinking about it. Well until I saw this thread!!
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It really is a rubbish feature in my opinion and in my car certainly not fit for purpose.
I drive from J4 to J11 of the M1 daily to get to work. When I come off at J11 I hit a roundabout within 100 yards, with S/S enabled it will stop the engine when I stop. I’ve been told that the tech will determine when not to stop the engine under certain conditions but it always stops the engine when logically it would be better to let the engine idle.
Again in my car, even after that run it will only manage 2-3 stops before it decides that it no longer can, presumably because of the battery level?
I don't know how much of this is accurate but it makes sense to me...
https://youtu.be/k159M8QhCIE
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Sounds like it will happen more often in an auto. I’m quite lucky as I have a 15 mile drive to the office which features 1 roundabout, 1 set of lights - so frankly I don’t do much stopping, aided by a manual gearbox which only cuts the engine when I choose to, that is only when in neutral at a standstill. I imagine in town, with an auto box I’d switch it off too!
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I'm disappointed that you didn't tell us as soon as this started happening. That way we'd have known that your stop start had started stopping sooner.
(Yes, I'll get my coat.)
Dave E
Skating away on the thin ice of a new day
My Beamer stopped stopping the start/stop when the aircon coolant was low. As soon as it was filled up, the start/stop started to stop again.
I figured the same explanation.
Someone who lies about the little things will lie about the big things too.
I am pleased to say that after a battery change my stop start has started stop starting
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I would be most pleased if the stop-start system in my car would stop working. No way to default it off and so needs turned off via a laggy menu every time.
Stop start is used in the WLTP calculations and contributes to the overall emissions number for your car. That's why you can't turn it off by default and have to each journey.
Knock on of it being off by default would be your emissions value going up along potentially with your road fund license cost or BIK value if you're a company car user.
Ally don't care much about the environment as long as car makes wrummmm.
Someone who lies about the little things will lie about the big things too.
Mine seems to stop/start when it fancies it but I usually turn it off when I get in the car anyway as it drives me mad. Mine's a button on the dash so easier to use than those that are within the settings.
Wish I could turn it off permanently in my F-Pace. It's just a nuisance especially at junctions and roundabouts.
Started out with nothing. Still have most of it left.
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