Piston Slap: Snowballing Concerns with Auto Start-Stop Systems
Greg writes:
I just read your article about someone wanting to disable their Start/stop function.
I have a 2022 MB GLS 450 (with the M256-E30 DEH LA-R, in-line six engine) with the ISG (Integrated Starter-Generator). My concern is that the engine oil does not lube the turbo bearings when the engine shuts off.
I read that MB did include an electric water pump to keep coolant flowing, but I could not find any information about oil pump flow. I keep my ISG off to safeguard the turbo bearings. I have noticed that when I have not manually turned off the ISG, under some conditions the engine will maintain a slightly higher RPM or may even re-start even when stopped.
Perhaps, MB has allowed for some conditions when the engine should not be off. My issue is when exiting a highway and then stopping at a red light, waiting for my turn to continue. This is when higher RPMs were present and then an immediate stop. I’m hoping for a good solution.
Sajeev answers:
Just so everyone is on the same page, running the engine to let the turbocharger’s bearings cool down is a real concern. It even resulted in an aftermarket solution called the Turbo Timer. The value of such a “cool down” has been deemed irrelevant with the advent of water-cooled turbochargers. That’s provided you change the oil and coolant regularly and don’t run your car in a 24 Hours of Lemons endurance race.
My confidence increases because I suspect Mercedes has another solution in place—as you’ve noticed, the system will restart when necessary. Finding documentation is difficult, but oil temperature is likely one (of the many) variables that factor into the ISG’s system tuning, with a measurement taken from the oil temperature sensor.
Something like an electric oil pump (similar to the aforementioned water pump that remains active) would theoretically be nice, but odds are it’s unnecessary. And implementation would be nearly impossible, as all vehicles use a mechanical oil pump buried within the engine. Even a complex and expensive dry-sump design still needs a mechanical pump at the bottom of the motor to get the system primed and pumping.
Mercedes’ ISG system (and all the others like it) are already exceedingly complex, and engineering a workaround for the oil pump introduces more points of failure. If there’s one place you want less complexity, it’s the oiling system. Failure in this area is far more likely to cause permanent engine damage, so the solution for you is simple:
- Trust Mercedes’ ISG programming to keep the engine running when oil temperatures mandate it.
- Change the oil and coolant regularly.
- Don’t skimp on oil quality.
- Do an oil analysis test as often as you need to ensure your vehicle is operating in a healthy manner.
- Have the “plumbing” for both oil and cooling systems inspected on a regular basis, and fix leaks to the system as soon as possible.
All this talk is enough to make me want a new EV over a new turbocharged vehicle. But that’s neither here nor there, so now I leave it up to the Hagerty Community to chime in!
I know this compares apples to oranges; however, I have a 2014 Mercedes E350 with an M276 3.5 V6 and 78,000 miles. Of those, the Auto Start-Stop function has never been defeated. I have also had similar experiences where I will be stopped at a stop light long enough, and the system will self-restart after stopping. It does seem to have a mind of its own on how long the “STOP” time is.
I have also noticed, though, that these conditions, as you started, have many factors, but one of them must be based on the temperature of the oil. I tend to run the same route daily, and the first stoplight I come to from my house in the summer, at 70+ degrees ambient temperature, the engine will “Stop.” However, during the winter months, when the ambient temperature is 50 degrees or below traditionally, the engine will not “Stop” at the first stop light I reach from the house.
I’m not worried much about the drivetrain’s longevity with the auto-start system being activated. I recently had my car in for service and was given a 2014 E350 with 275,000 miles on the original drivetrain. The car ran flawlessly and gave me hope for my car. I asked the mechanic how much work it has taken to keep the 275,000-mile car running, and he said, “I’m cheap labor, but it’s not needed anything out of the ordinary; it’s on the original starter and, of course, engine. Just keep up with your maintenance and listen to me; your car will go that far if not longer. ”
So now Auto Stop-Start is no longer on my ‘worry list”.
However, the hydraulic braided convertible top lines are a real fear that comes closer day by day!
You have a very large V engine large pistons and best styled engine for dynamic balance and and most probably well overpowered for your journeys. Try the rubbish they are pumping out now, underpowered 1ltr. 3 cylinder all in the name of environment friendly, what a load of rubbish from brain dead politicians and armchair engineers who obviously would need to be told what a spanner was for.
3.5 L is “very large”?
That’s a decent V6, but hardly “large”.
Those Euro taxes and experiences have warped your concept of size.
Huh?
You don’t like environmentally friendly?
Not at all because it has swung too far left of common sense. Average hydrocarbon & co2 vehicle emissions have never been lower. BAN diesl engines in non commercial vehicles if the environment is a concern. I’ll never buy an all electric vehicle.
I’ve been concerned about the life of the starters in stop-start vehicles like my Highlander. I hate that feature and turn it off once I start up.
I got into the habit of shifting my transmission into neutral just before my vehicle comes to a stop. Defeats the auto stop start system on my truck.
just get the relay that disables it
It is the coolant temp that determines if the engine can be shut off. It is done for emissions reasons to keep the engine above the temp where warm up enrichment isn’t required.
From my experience with Honda and Infiniti systems, coolant temp is the main variable in all stop start systems. Especially in cooler temperatures where it may be necessary to keep the motor running to create enough heat for the heating system.
ok so there are a multitude of things that the stop/start looks for but these are the most common- engine temp and oil temp (too cold or hot), AC needs (usually when the interior temp is more than 5 degrees from what is dialed in the engine starts to run the compressor), battery charge voltage (too low it starts the engine). On the VW and Audi cars moving the steering wheel (on an electric power steering car) or changing the brake pedal pressure will start the car as it is anticipating you are about to start driving, some of the American cars I have rented do not do this. When Audi first used this system about 13 years ago there was a large list of things that could influence the system.
The bigger issue to me is valve health. In my Ecoboost, the only time the throttle body injector runs (the only means of cleaning the valves) is at idle. If the valve stems aren’t cleaned they cake in DI motors, meaning the auto start/stop negates the TBI’s ability to clean valve stems. Considering how many manufacturers are now recommending valve stem cleanings now, this is clearly a known issue. Prior to DI motors, the injectors sprayed fuel over the valve stems, cleaning the cake caused by the CCV. No engine will last long with carbon caking on the stems for a miriad of reasons. Considering auto start/stop isn’t mandated, I really wish manufacturers would offer some means of disabling it.
It’s interesting that on my 2019 M5 BMW the auto start stop STAYS disabled when I restart the car. occasionally the thing seems to revert to stop/start when I go through the car wash but I’m convinced the dude taking the car to the wash hits the area below the stop/start button to re-enable the stop/start.
Lots of cars have a button, or screen icon, that disables the stop-start.
True, but I think some guys are looking for a way to permanently disable it. There are a few solutions on YouTube but most are inelegant.
True, but many cars simply re-enable the start stop next time you start the car.
My auto start stop button on my 2023 Jeep GC L resets to active upon every restart. Seperatly I thought the restart was triggered by battery voltage drain when motor is off rather than oil temp. I mean how much can oil temp drop at a red-light?
Probably Zero oil temp drop. There is a lot of very hot metal Tom keep it warm. It may increase a bit due to the lack of coolant flow…
Takes a $120 Programmer to bypass the button resetting every time you turn it off.
I think dealership could do it but they charge 200 or say the government won’t let them do it.
The greatest issue here is the lack of understanding on just how these auto stops work and all that is programmed into them.
There is a ton of variables that determine when a system stops or not.
Things like running AC full, heater full, stopping for more than 2 min in some will restart, if the engine is running hot, if the engine is not up to temp and more.
The Turbo oil remains in the turbo after stopping, the water cooled housing stops coking. Synthetic oil also plays an important role.
I think many will find Turbo failure is often due to poor oil changes, wrong oils and poor coolant.
Also these small turbo chargers are not always the best they could be due to cost constraints.
The reality with many of today’s cars these smaller and boosted engines are just not long lived. I know many of us watch the Car Wizard on YouTube. He points out many cars todsy are good gor 100k miles and after that they become money pits.
Things like failed timing belts and chains along with other major issues can make it impossible to repair at a price worth saving the car.
He just had a Lincoln on this week with just over 100k miles and two failed Turbochargers. It would cost more to fix than it was worth.
This is not just a ICE issue. EV and Hybrids can bleed even more money. I saw a Malibu Hybrid eith just over 100k miles but the battery needed replaced. The car looked great but the battery cost more than the car is worth.
Many Hybrids and EV as they age will be like an old IPhone with a dying battery and an old tech no one wants.
The government regulations on MPG and Emissions mean well but we have passed a tipping point of affordability and reliability. They need to balance this for the consumer or no one will afford these cars.
But beware. There is a move to oust for less lanes in the roads and to make traffic more an issue. I’m sure you seen the 4 lane streets cut to two lanes with a bike lane no one uses.
They also are promoting trains and public Busses that most of us can’t and won’t use. We are too spread out vs much of Europe. What works there is not going to work here. Texas is proof of that.
Hey Hyper, I am curious about this comment you made about the move to congest streets. Can you cite some sources or a published bill or plan? I feel like that’s a pretty big claim and would like to be better educated if you have a trusted article or a bill you can share.
And personally, I don’t mind public transportation as long as it keeps crummy drivers off my streets.
Hey Joe, the city of Cincinnati is doing this all over the city for bicycle. And it really causes a lot of congestion!
The same thing has happened in my city and cities near me. They are changing roads from 4 lanes to 2 with bike lanes and a turning lane in the center. (I have heard it’s due to federal regulations or something)
https://highways.dot.gov/safety/other/road-diets/road-diet-informational-guide/1-introduction#:~:text=The%20reduction%20of%20lanes%20allows,parking%20(see%20Figure%202).
Thank you, Tyler. I appreciate you sharing seeing facts rather than opinions.
Joe it is not opinion. It is more about agendas and appointed people to government agencies to spread the agendas.
This is for the thinking man you need to dig a bit deeper than the propaganda.
The complaints here are not just random peroneal thinking it is the general consensus of most in the cities that have adopted it.
You may love the but but in most areas public transit is not an options and if it is can be downright dangerous.
The Bart train in SF is great. But the Subway in NYC is pure hell.
In the near by city the buses are inefficient and time consuming. They drive around mostly empty and they seldom go where you live or need to go.
They could replace them with vans and save more fuel.
Much of this info is right there on google if you are only willing to look.
I’m not trying to attack your stance, only to gain clarification. A thinking man asks questions and is curious. He doesn’t take the word of random people in a comment section as gospel.
Tyler answered my question. Thank you.
In Minneapolis they changed a street to include bikes, walking path. Narrowed the auto lanes such that some fire trucks could not pass on the street. Even with no residential parking on the street.
WoW–as someone who hasn’t rode a bicycle in at least 25 yrs– I love when Bikes are separated from cars– & if we can get Lots of folks using Public transport/bicycles ect ect the roads will be less congested –we’ve already “Tried” building more & bigger roads & that has Not worked– Think (Rationally ) about it-
I’m guessing you live in a city, Jane.
Dayton (famous for a couple of bike mechanics) has a separate highway system just for bicycles, mostly made up of former back alleys and unused rights-of-way. It works pretty well, if you’re careful about where it crosses car streets, and is completely discrete from motor traffic. Couple of NE Ohio counties have committed to separate stone roads just for Amish horse traffic and bicycles — taking us back to the days of the Good Roads movement, when bicycle lobbyists agitated for navigable pathways. Trouble then, and trouble coming now: at some point, e-bike, powered bike, and then ATV users will want to use this network.
Oh, it’s definitely a thing. It’s called a “road diet.”
I live in a Boston metro area and they are not only planning this, but it is currently under construction everywhere we drive, the inner city limits of Boston and surrounding cities as well as all roadways leading in and out. Lane reduction didn’t need any legislative bill to begin the process, but it was all in the name of public safety allowing safe passage for those on bicycles (who don’t pay attention to any road rules), and special bus lanes “only” during several deemed busy times. The congestion is going to raise those temperatures that run the car systems. I drive a 2023 XT4 and have been trying to see if gas consumption is better using their system, but after reading this article it sounds as I should disregard care of that.
City of San Jose has done it on many main streets.
This summer on a street I use in my daily commute they did convert a big stretch of it from 4 lanes into 2 with bike lanes on either side and a bunch of barriers between the bike lanes and the road. You are correct that I have never seen a bicyclist on it. I think a big chunk of that is due to the fact that just a block or so away there is a dedicated bike/pedestrian path on an old railway right of way. But the city got a bunch of money to make for safer biking. Now to be fair it is not a high volume road so the change to 2 lanes hasn’t had an impact on traffic at least during the times I drive it.
On another section of road on my commute path they changed it from 4 lanes to 2 in one direction, 1 in the other and a two way left turn lane and it was promoted by that city as a “traffic calming measure” that they claimed would lower speeds. Of course it hasn’t done that as people still drive 10+ mph over the unchanged speed limit.
Yes much of this is federal funding and counter to the smooth traffic we once had.
Same on round abouts. They are claimed to be safer. They may have less deaths which were few but accidents are up. People have no clue how to use them.
We have a few you have to cut off the other driver to move to exit if you go 3/4 away around it.
The speed rams have damaged some low sitting cars that were not speeding.
Where I live, they have installed a number of round abouts at intersections that had high fatality rates. One of the ones that so many complained about is now 3 years old and guess what, only 1 fatality and a much lower accident rate. I travel thought that intersection often, and it’s much easier to cross the busy highway. It’s been funny to talk with some friends now who do admit their complaining was over nothing and they like the round abouts now.
Sadly, there are a number of folks that don’t seem to know what “yield” means and then there’s the old folks who stop at the yield sign………
That is the trouble here is Yield is a unknown factor. Some stop when they should go and others go when they should stop. While fatalities may be lowered. Not many were happening we have more fender benders.
It is not just old people many young people texting are just as guilty.
Round abouts are a nightmare with a trailer.
We have a few around Phoenix and there are big signs warning people to yield for trucks with trailers. Especially semis. I just run through the center now because it is way too much hassle otherwise. Especially with the gooseneck. When towing horses it is a slow creep and endless honks from the impatient Phoenicians and SnowBirds escaping their near death.
No one yields, no one pays attention to the trailer swing, so if I can’t use both lanes, I run over the median – which are typically paved or lined with bricks.
My group completed a traffic engineering study for a wrongful death trial and concluded that the rate of fatal accidents could be dramatically reduced by increasing the all-red time delay by 1 second.
Right there is probably the #1 problem with roundabouts. They are too small. The exits are too close together. Local town closed a “dangerous” intersection. Put in a bypass with a round about. Problem is one of the exits point right at the “dangerous” intersection that they closed. County engineer at his best.
Roundabouts in Europe are common and generally a bit larger than those here in NA. I drive a semi and have to run the trailer wheels up on centre berm to get around most. The other issue is I need both lanes due to vehicle size but there is always some driver who will try to negotiate the traffic circle with me, then flip the bird because I’m taking up 2 lanes.
Is the 24 Hours of Lemons intentional? I’d love to see that race.
It is a real event, google it.
Yes, it’s real. Used to be sponsored and promoted by Car & Driver magazine. Don’t know if C&D still involved or not. It sounds like fun.
Roundabouts are great if drivers know how to use them. I’ve driven them in Europe without a problem. Here in the states, not so much. Drivers here are unwilling to ease up a little on approach in order to allow a car from a different road to enter first. Roundabouts are essentially on-ramps for intersecting roadways and much like an interstate on-ramp, traffic moves more efficiently if both drivers time their arrival to allow a zipper effect.
I have a 2017 Toyota Highlander with the auto start-stop. It works OK, I guess. But it IS annoying when the light turns green and you have to wait for the engine to turn on.. also, during the summer with the AC blasting and the engine (and the AC compressor) turn off and you are blowing hot air.
The biggest contributor I’ve seen for the engine cycling back on when stopped is the battery level. It takes a lot of power to run the HVAC, lights, and radio.. I especially noticed this when we got a new battery… With the old battery, we didn’t really notice, but the auto-stop-start hardly operated.. once the new battery was in, it would activate AT EVERY LIGHT. So clearly battery health and capacity have a significant role to play in how aggressive it is.
But here is a real kicker.. the computer keeps track of the engine starts and will REQUIRE you to replace the starter motor after 384,000 starts, weather it still works or not.
The one thing I find especially annoying is we will pull into the driveway and stop, the engine will stop, then we put it in park, which reactivates the engine.. then we turn it off and get out…. It’s an unnecessary stop-start just to turn off again.
Is it safe to assume that the 48 volt Integrated Starter/Generator has fewer moving parts to wear out, compared to the 12 volt conventional starter in the Highlander?
THE START AND STOP FEATURE ON MY LINCOLN CORSAIR IS THE DUMBEST IDEA I’VE EVER DEALT WITH AND IT’S JUST ONE MORE WAY OF CAUSING PREMATURE STARTER FAILURE AND ADDING UNNECESSARY STRESS ON A DRIVER WHO THINKS A VEHICLE SHOULD STAY RUNNING UNTIL THEY DECIDE TO TURN IT OFF. THERE IS NO WAY TO PERMANENTLY DISABLE THIS UNWANTED AND UNNECESSARY FEATURE THAT MAKES ME HATE DRIVING MY CAR. IT’S A STUPID AND FORCED FEAUTURE THAT SHOULD BE ILLEGAL.
You are absolutely correct. Just an awful system that is being forced on the American public. I drive a 2021 Volvo XC 60 that allows me to perminately turn the start/stop feature off. The vehicle has 30,000 miles on it and the feature has NEVER been turned on. I had planned on getting a 2025 Volvo XC60 but the new models have no way to turn the system off. Volvo has succeeded in losing me as a customer–one who has driven Volvos since 2012. Word of advice to Volvo, don’t tell the American public how to drive their cars, give me the option of turning off a useless system that is nothing but a pure aggravation.
There is no need to have a complicated electric oil pump to provide a little oil pressure on restart, or to send some through the turbo on shut down. An accumulator like an Accusump would do the trick. With an electronically controlled valve you can hold and then release the pressure just before the restart event to prevent a “dry start”. W/o a valve it can provide some oil flow after shut down to prevent oil coking in the turbo bearings. I am a bit surprised that to the best of my knowledge no mainstream mfg has implemented such a strategy.
On the other hand Toyota implemented a heat harvesting and storage system in certain years of their hybrids. Essentially a thermos type device that has a coolant loop just through the head. On shut down as the coolant in the head continues to increase in temp the electric pump harvests that extra heat often significantly above the normal operating temp and then stores it. Upon restart it dumps that coolant into the head to shorten warm up time and reduce the need for warm up enrichment.
Oh gosh this takes us back over a century! The main purpose of riding mechanics on racecars was to manually pump up oil pressure after magneto shutoff, before carbs with throttles worked. I’m told they’d smoke a little when re-fired…
Do your homework. There are several sources that make plug-in modules to allow the user to set the start/stop default to disabled. In other words, every time you make a fresh start in the vehicle, there’s no need to press the button to disable the system.
I paid about $100 for the plug-in module I bought. I don’t know about any potential effects with regard to warranty. I don’t think the ECM or BCM can see the module. I can see any difference in scan codes or live data.
Ok, first and foremost engine start stop is based on electrical load and the battery state of charge. If you have many accessories running and the battery is not above a specified charge level the engine will not stop or may prematurely start back up. There are other factors involved sure but the system is first looking at the electrical system.
As far as the turbos are concerned there should be a check valve or a few to prevent oil from escaping right away. And unless you are constantly hot rodding around I would be concerned with burning the oil in the turbo bearings under normal driving conditions.
I’ve passed nearly 400,000 miles on stock turbo, 50% towing. No stop start.
The .5 mpg savings over the life of the truck is minuscule, about $2,400 in today’s dollars. Over 100,000 miles? Not really worth it. I’d pay $600 to deactivate such a nanny doogooder feature.
thankfully its under $100 on most cars to disable this
I bought a new Mazda in the past year with the SkyactivG engine and was pleasantly surprised that 2024 versions of my specific model and trim didn’t have either auto stop/start or cylinder deactivation due to supply shortages. Both features are back in the cars this year. I don’t care about the single city mpg the features were said to have gained me, especially when cylinder deactivation is known to cause multiple troublesome issues on these engines. I went for the non-turbo engine, too. Less complexity, cost and maintenance down the road.
I had a cls63 with auto start/stop. If I spent more that 10 mins in traffic I used to turn it off, because that big 5.5l twin turbo V8 didn’t like it. Otherwise a fantastic, wonderful car.
Very good info
This is one of those interesting and probably unnecessary disputes like which direction to hang the toilet paper roll. My collection is too old for me to have to deal with this feature, and will probably stay that way because the government and picky consumers have all but killed anything interesting about the automobile. In the few cars that I have driven that has this particular feature, when it gets on my nerves, I just push the little button. The starters are designed for the extra service, and your warm, previously running engine isn’t that hard to start anyway. If I was going to disable a feature on a newer car, it would probably be the link to Skynet and all of the nanny driving aids, and this one would be very low on my list.
I’ve disabled the Auto stop feature on my 2019 Ford Ranger. It was a simple plug on the OBD port for $100.
I can turn it on any time I want with the original switch, but I don’t.
I love my truck and this would bother me every time I came to a stop.
Problem solved.