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Temps are way too high for a 15min drive. Gearbox temp even more so, considering it doesn't heat up nearly as fast as the engine. For gearbox 85°C is of the highest I've seen and that's after several runs at 25-28°C ambient. For the engine I've seen 105°C again after several runs (spirited driving would be an understatement), but it only takes a few minutes of normal driving to drop back down to about 92°C. Our oil cooling system (cooler and whatever else is involved) is impressive, it's one of the things I'm mostly impressed with. If yours is failing, might explain why it's going into limp mode. How long does it take for the engine to cool back down to let's say 90°C?

So are the high temps the culprit of losing turbo power?
 

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There's just so many things that might be causing it, that's where I'd start looking. Gearbox temp specifically, which should heat up a lot slower. I've never seen anything above 86-87°C and like I said, that's after several consecutive runs, and you got 91°C in 15 mins. Same goes for the engine, you got 100°C in 15 mins which doesn't seem right. But I've seen 105°C (albeit after several runs, not 15 mins) and didn't notice any power loss so I doubt the engine temp is throwing it into limp mode. Now, whatever is the cause, it won't change the fact that both your temps are way too high for a 15min drive. Maybe it's a sensor and not the cooling system. It'd be helpful to check how long it takes for the engine to cool back down from 100°C to 90, while driving normally, at let's say 25°C ambient. No need to check how fast the gearbox cools down because that always takes a while. It both heats up and cools down a lot slower.
 

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In my country here we have summer all year long as we are near the equator, so during the day time the ambient temps can go as high as 40 degrees.

I've had both my engine and transmission temperature hovering over 90 degrees after spirited runs and the car doesn't cut power.

I've shared previously that I had a hidden error code which wasn't showing on the dash but an OBD scan revealed it. The engine isn't producing any power because the car is running on limp mode.

Rather than trying to guess and shooting in the dark, if you can get your car OBD scanned it will tell you whether there's anything wrong.

Sometimes, the check light only comes on after couple of engine on/off cycles.
 

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^ That's better advice than mine. Agreed.
 

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Hi,

Took delivery of my A45S (Designo Mountain Grey Magno A45 S AMG ) from Mercedes-Benz of Edinburgh East mid April 2021. Lovely car but only managed to put 1500 miles on the clock so far and mainly short journeys in Comfort. Early on I got a couple of "Transmission Errors". Nothing since but there is definately something odd going on with the transmission which means at times there seems to be no power or something doing a CTL-ALT-DEL!

Craig
It's not uncommon in C in my experience. Especially where I have done manual changes and then resort back to auto. The box seems to need time to think.
 

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@DL45s look for crankshaft position sensor / top dead center sensor. If it's not the spark plugs, this could be the culprit and the error may be stored in memory.

I haven't told you guys that I've been experiencing similar power losses / hiccups, but just never went into limp mode. Lately only noticed a few brief hiccups in 3rd-4th gear and always in higher rpms and when gearbox temp is above 85°C (by that time engine oil is always above 95°C). Felt like misfiring but without the characteristic exhaust sound that it comes with. I've been trying to see whether there are any patterns in replicating it, before taking it in for inspection. So last night I pushed it hard enough that temps climbed to 105°C and 95°C respectively and even launched the car like that. Had a perfect launch, all the way to 4th gear and then had a massive power loss, felt like I hit a wall, worst ever.

It felt pretty much like the following video of a W176 A45:


Only difference is it felt like one massive cut off, not 3-4 in a row like in the video. And I still had power, I was just afraid to keep flooring it. It didn't stall, turbo was still running like it should, I just lifted off and laid back for a few minutes (but still felt as though power was still available), keeping it at 60mph until temps went down to 90°C and did another run, a 1st gear roll this time. Everything seemed normal, no hiccups, no massive power loss no nothing.

I looked it up, did an extensive search and I really do believe it's a faulty crankshaft position sensor / top dead center sensor. I can't explain how it's related to temps, but it has to be, because it never happens below these temps. And it also only happens at WOT. I don't have the most serious symptoms such as CEL, engine not starting, or engine stalling, vibrating, rough idle etc, but these hiccups and power losses are some of the symptoms too, even if everything is back to normal just moments later.

Monday I'm taking it in for a scan, because it's the right thing to start with, but I'm gonna tell them what I've been thinking. I really think this is it. I'm actually curious to see if I've nailed it.

I'll get back to you.
 
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So things came up and didn't have time to take it in, but been taking the car every chance I get and it's been running fine since.

So here's what I've been thinking. We had a severe heatwave that lasted over a week when it was acting up, I'm talking extreme humidity and high temps even at midnight, you'd sweat just standing there, horrible conditions for a car running this much boost. Well after heatwave was gone and humidity dropped to 50% it all stopped. Been doing all kinds of roll runs and haven't noticed not a single hiccup. Can't be fueling issues such as injectors and fuel pump, never heard of fueling causing intermittent problems in identical runs (1st to 4th gear). Can crankshaft position sensor cause intermittent problems? Maybe nothing's actually failing and it's down to air-fuel? Members have reported getting several software updates that sorted everything. What kind of updates are these? Re-adjusting safety thresholds? Does that make sense?
 

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So I'm now positive it's not related to engine/gearbox temps, or humidity and I also doubt it's the spark plugs as half of the time it runs flawlessly. The problem is intermittent, there's no check engine light and I've noticed I'll either get hiccups (above 5k rpms in 3rd and 4th) for the entire session, that is from engine start to shut down, or it'll run flawlessly, again for the entire session. Few days ago I took it for a drive and I think I did a couple dozen 1st to 4th gear runs, went through half a tank in test runs and everything was fine, with engine and gearbox at 103°C and over 90°C respectively. Almost forgot, I always go to the same gas station, at the same pump too.

Now got another update and here's where things start to get interesting. Pops and bangs are gone, entirely gone. Except emotion start, that's still there. I think they stopped about the same time as hiccups appeared, just never really noticed until last night. Exhaust sound hasn't changed though, and the exhaust button works the same I haven't noticed anything. So I did a search and got this:


(props to @changchewsoon)

Which means there has to be something registered in the ecu. There has to be something that it doesn't like and it killed the pops and bangs to protect something, same with hiccups. That has to be another safety measure and I think the two are closely related.

I was gonna take it in in a couple of weeks but I think I'll be able to make it Monday, will let you know.
 

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TLDR; took it in, the error was A/F (no CEL), diagnose was bad fuel. Was advised to switch after burning as much as I could. Shortly before refueling, handheld vaccum sound from under the car, CEL, engine sputtering and stalling, but was able to start after a few minutes. Took it in, second diagnose was bad low pressure fuel pump (in tank pump).

As expected there was an A/F registered error. You always start with the simple stuff so first diagnose was bad fuel and was advised to switch and see if that solved the problem, but first it'd be a good idea to burn as much as I could but no hard accelerations no high revving.

Left dealer, and as I had a little over 1/3 in the tank and plenty of free time I decided to go on a long drive. Everything was fine until just under 1/8 in the tank (was about to refuel) at the stop light, when I hear a medium to high pitch sound coming from under my seat or the passenger seat I dunno, but definitely not the engine. Sounded like a handheld vacuum with short pauses in between. You may already have some idea by now right? And you're not wrong. Knew something wasn't right so light goes green and I keep it at 20 mph. Moments later I get the CEL and car starts to sputter and just as I was about to pull over the engine stalled and got a christmas tree dash. Just let the car roll and pulled over safely, was lucky it was a low traffic road with plenty of space to park. Tried to fire it back up, was cranking but wouldn't start. Got out tried to think whether it'd be best to have it towed at home or at the dealership which was already closed by now and generally wanted a moment to pull it together as I was totally not expecting this from a hand built AMG car with less than 10k miles on the clock. 4-5 minutes later I got back in the car and I dunno why, but something kept telling me to give it another try, and it worked! Not only did it start effortlessly, you wouldn't even tell something was wrong, aside from the CEL that was still there. The weird sound was gone but I kept going slow trying to get home without another surprise.

Little did I know it was all but over. Car was good for 10 minutes and the sequence started once again, weird sound, CEL was already on, sputtering until it eventually stalled, except this time leaving me in the middle of a 3-lane avenue that I was about to cross, with tons of traffic! It would crank but not start so I immediately got out and went to grab the triangle as I couldn't be sure waiting for a few minutes would work this time, and I had to warn the other drivers while I was blocking the street anyway. However 3-4 minutes later I did get back inside and gave it another try, and again, it worked! Put triangle back and drove until I got home and actually barely got there as it stalled in my garage as I was pulling close to my space, had to wait for it to start once again to move it a few more feet. And that was the end of my day.

First thing in the morning called dealership, explained what happened in every detail and they advised me to take it in if it was still driveable, otherwise have it towed. Should I top up fuel on my way to your garage if driveable, no best take it in the way it is (unless too low on fuel of course, but that wasn't a problem as they are under 6 miles away). Car started perfectly normal, minus the CEL and also just a little fluctuating rpms while waiting for cold start to complete. Got to the dealership without problems and left it there, stayed for about an hour in case they could at least put it on the scan, but they had too many cars to deal with so it was pointless, but they insisted it may still be down to bad fuel. Had my wife come pick me up and waited for their call. At least had a perfect Starbucks breakfast.

Call came next morning (earlier today that is) and they said it's the low pressure fuel pump (which is the in tank pump). They ordered a new one which is supposed to arrive tomorrow actually, so guess I'm lucky. And now the wait begins, as I'm sure it'll take a few days. I suppose they're gonna check the fuel filter too while they're at it, which btw will be a good indicator as to whether fuel is responsible in any way, cause I need to know if I should switch fuel. Btw I haven't changed gas station in over 10 years (it's a Shell). In fact all cars in the family, some high performance cars too (aside from the A45s), and neither car had a problem. On the contrary, some cars are even highly tuned and require no less than 100oct, clean fuel, so if there was something wrong they would be the first to report. I even told them that, when I took it in the first time before the CEL appeared but they said that every car is different, ever fuel pump and fuel filter is different so you never know where the problem will hit. Yes, I was boggled by their answer but like what else could I do, I played along, I mean car is under warranty anyway. But I really do want to know how's the filter so I'll be sure to ask.

Yup, first A45s with a bad tank pump. Add that on the defect list. Oh almost forgot, at some point I'm gonna have to take it in for a recall on some joints/hoses/fittings (didn't really understand) in the AC. Said I may never have problems but they should still be replaced. But that has to be done at their other garage which is further away from my place, as they don't have the proper equipment. Am I ever gonna buy another car that's been out for 2 months? Let me think.

That's for anyone else having similar symptoms.
 

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Wasn't a long wait after all. Got the car back earlier today, old pump out, fuel tank cleaned, new pump in, BP Ultimate Unleaded 100 top up and test drive. No errors.

Didn't do any runs as it was too hot today which was enough strain as it is. Also wanna see how it drives for a few hours before doing any runs. But that has to wait until Monday as we're leaving for the weekend and we're not taking the Merc. So far so good though. Filter wasn't in terrible condition but considering my low mileage, it didn't look that good. They put some fuel in a plastic water bottle for me and it seemed pretty clean, but when I looked inside the pump, I saw gunk, not too much of it, but still... Though I'm not sure this killed my pump, for all I know it could still be a defect. Guess I'll never know. Anyways, I've already switched to BP 100oct as was advised and I'll see how it goes in the long run.

For anyone interested, the first error code (no CEL) was related to A/F which was an indication of improper fuel delivery. Symptoms were basically hiccups but only at WOT and always above 5k rpms though not in every run (hence no CEL) and sometimes even massive power loss; both symptoms were obviously counter measures deployed by the ECU.

Second error code (with CEL) was P008A (Low Pressure Fuel System Pressure - Too Low) which was telling us that the tank pump was unable to keep up with the requested pressure. Symptoms worsened considerably, to the point it made a loud handheld vaccum sound and sputtered even at 20 mph and eventually stalled. The two codes are obviously closely related.
 

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Thanks, yep it's been a relief, just hope car remains reliable from now on.

Guess had I scanned for errors, I could've sorted it out weeks ago as it was a simple replacement, but I never thought a failing tank pump could have intermittent symptoms, that's usually a sensor. So I looked into sensor related cases and actually found one concerning our cars, it was the crankshaft position sensor. Symptoms matched almost perfectly. But you can't always identify the cause by the first error. A/F was so generic it could've been several other things, fuel injectors, fuel leak, even a sensor. I've had the first mild symptoms since 2 months ago, but it wasn't until I got the CEL along with the more serious symptoms that the error became more specific and finally led us to the cause. And even that might've been a clogged filter, not necessarily the pump. Though the sound it made on its way out was a strong tell. So yeah, sometimes it can take time and drive you crazy in the process.

Can I ask why you went with obdlink mx+? What's more special about it? Did you look at others as well? And overall are you happy with it?
 

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Your experience has reminded me of another poster on the forum, who belittled today’s technicians who didn’t know any better than to plug in a diagnostic machine and to do what “the computer told them to do”, and harked back to the days where a “proper” mechanic fixed their car with a watering can and “proper” know how, hitting the correct component with a hammer etc.

The truth is that todays modern cars have over 40 ECUs and more than double the number of sensors, you just have to have diagnostic codes mixed with a skill set of experience and technical know how to be a good diagnostician.

First step — unless the problem/root cause/solution is staring you in the face, the first step is always to do a scan.


And then work out if it’s a sensor fault or if the code is actually pointing you in the right direction! :p
 

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I should have scanned for codes since the very first hiccup, I was so wrong not to. I'm nearly ashamed of actually thinking it was the humidity, haha.
 
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Thanks, yep it's been a relief, just hope car remains reliable from now on.

Guess had I scanned for errors, I could've sorted it out weeks ago as it was a simple replacement, but I never thought a failing tank pump could have intermittent symptoms, that's usually a sensor. So I looked into sensor related cases and actually found one concerning our cars, it was the crankshaft position sensor. Symptoms matched almost perfectly. But you can't always identify the cause by the first error. A/F was so generic it could've been several other things, fuel injectors, fuel leak, even a sensor. I've had the first mild symptoms since 2 months ago, but it wasn't until I got the CEL along with the more serious symptoms that the error became more specific and finally led us to the cause. And even that might've been a clogged filter, not necessarily the pump. Though the sound it made on its way out was a strong tell. So yeah, sometimes it can take time and drive you crazy in the process.

Can I ask why you went with obdlink mx+? What's more special about it? Did you look at others as well? And overall are you happy with it?
It was my tuner who recommended me to get it because many of his other customers had reported good experience with it and it supports over the air firmware update via the app.

And also the OBDLink MX+ also allows them to perform some logging but it is quite basic however and nowhere near the tools that is being used by the tuners as the channels are quite limited and the logging frequency is probably not as fast.

Still, any logs is better than none especially for his customers that are not within the same geographical area, such as the Middle East for example. I remember he was telling me that the ambient temperature there was so high (out of his expectation) that had he not seen the logs himself he couldn't believe it.

Plus it is quite affordable, I keep it in my glove compartment so in the past I could quickly perform a scan whenever I sense something is not right in the early days when the car is being tuned, especially it was being done remotely.
 

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Thanks. It should make my life easier considering I wanted to take the car in for code scanning so many times (after the first hiccups) and just didn't have the time.
Think I'll buy one too. I've found 2 local shops that have it available for dispatch.
 
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