CX-5 stalled at high speed

[Moonlighter]

One thing you really have to get used to with radar cruise control, is to get into the overtaking lane well before you catch the car ahead.

Otherwise it will just slow down ever so gently to match that car’s speed, and it can catch you out - you look at the speedo and realise that you aren’t going as fast as you had set it. And now you’re stuck behind that car with traffic whizzing past in the passing lane.

You may have seen that you can adjust the following distance - how far behind it will follow.

I wonder whether something weird just happened and (I am assuming) that you accelerated to overtake and maybe at that moment had gotten what it saw as too close, and the car automatically braked at the same time??

Possibly the 2 contradicting events - the car wanting to brake to avoid a collision it had anticipated, and you accelerating firmly simultaneously- cause it to throw a hissy fit??

I would suggest you adjust the following distance to the max and go for another run, bearing in mind that issue of changing lanes well before you catch the vehicle ahead. I am thinking that it is unlikely to replicate the behaviour.

Radar cruise control is a terrific feature. I now have a Mitsubishi 4WD dual cab as well as the (mainly wife’s) CX5 and it just has traditional cruise control, and every time I drive it I curse the fact it doesn’t have radar cruise control. I really miss how good it is.

 

[ADS-B]

I wonder whether something weird just happened and (I am assuming) that you accelerated to overtake and maybe at that moment had gotten what it saw as too close, and the car automatically braked at the same time??

Possibly the 2 contradicting events - the car wanting to brake to avoid a collision it had anticipated, and you accelerating firmly simultaneously- cause it to throw a hissy fit??

If you intentionally accelerate, you press the acceleration pedal, you override the brake. The car won't brake, it will let you go.

 

[Moonlighter]

If you intentionally accelerate, you press the acceleration pedal, you override the brake. The car won't brake, it will let you go.

So you’re saying that when it has activated emergency braking and you then accelerate, it will release the brake???

I dont know if Id be game to test that…..

 

[Allen.z]

This is a serious safety concern that deserves their full attention.

 

[ADS-B]

So you’re saying that when it has activated emergency braking and you then accelerate, it will release the brake???

I dont know if Id be game to test that…..

That's exactly what I say. The driver has the ultimate authority. You want the car to respond to your command, not to override you. Not just the acceleration pedal but also the brake pedal. The car initiates the braking and let's say you get scared and your first impulse is to press the brake pedal. Your brake input overrides the car's self braking. I hope I explained it right.

 

[ADS-B]

I guess you could try it with a big bale of hay in an open field somewhere, I don't know.

 

[N7turbo]

So you’re saying that when it has activated emergency braking and you then accelerate, it will release the brake???

I dont know if Id be game to test that…..

In this instance, I don't believe we're talking about the Smart City Brake system.

 

[Moonlighter]

In this instance, I don't believe we're talking about the Smart City Brake system.

What else then would make the car suddenly brake?

 

[N7turbo]

What else then would make the car suddenly brake?

I went back and saw where he said it started braking. I don't know, but I think two things are getting mixed up: the car braking to match speeds with the car/object ahead, and the emergency (hard) braking from SCBS which is an entirely different thing.

 

[Moonlighter]

Look we are all tossing around ideas and thoughts here to try to help the OP. Not to get one-up on each other.

Anyway…

SCBS doesnt operate at the speeds OP said he was doing, its max is around 50mph. He said he was doing about 72mph.

Mazda’s owners manual says that the normal warnings you would get when using radar cruise control when rapidly approaching a slower car will not happen when you are accelerating at the same time. If I read it correctly.

OP - can you help by throwing a big more light on what happened, and tell us again:

1. how rapidly were you closing on the car you wanted to overtake?
2. Can you toss us more information about the braking you experienced - did it actually feel like the brakes had been applied and if so how firmly? Or are we talking about a simple loss of power and slowing due to engine braking?
3. Had you actually completed the lane change, or were you still part way across, when it happened?
4. Did you hear any alarm beeps at any time?

Also, could you do me a favour and humour me just a bit…..

Check the battery connections/lugs. Look for any signs of corrosion. Put a spanner on them both and see if they can be tightened. If in any doubt at all, undo the lugs and clean both the connectors and lugs so they are bright and shiny metal. Tighten firmly afterwards.

Reason is that all kinds of weird things can happen when these modern cars have less than perfect power supply to the ecu. An old battery, poor connection, corrosion etc can all cause problems. I have seen cases eg one where a full turn tighter on the battery lug bolt resolved a weird transmission issue on a BMW.

 

[Moonlighter]

Also, on the fuel filter issue….

A few years ago on our previous CX5 2.2D, I had a strange thing happen one day - car would crank over strongly but would not start. There was zero indication of wanting to start. No firing at all.

Called our roadside service assistance service, they came out and put the scanner onto it. No codes. Everything looked normal.

He actually asked me if I had fuel in the tank, he suspected no fuel getting to the engine. I had filled the tank only a day or so earlier so knew the fuel gauge showing at 2/3 was a true indication.

Couldn’t find any issue on the scanner.

Turned it off and then, just to test it again before giving up he pressed the start button again and damn me, it started and ran as normal. Turned it on and off a few times, all back to mormal, he even checked the fuel pressure - pretty good.

Anyway we agreed that it sure wouldnt hurt to change the fuel filter as we both suspected a fuel delivery issue. So i got that done the next day at the Mazda dealer and the problem never recurred.

I had alerted the dealer to the reason for the filter change and asked them to empty out the contents to check if that revealed anything…. It didn’t.

May be worth considering a fuel filter change… up to you. If you do that, make sure they use a genuine Mazda fuel filter. To be sure, to be sure.

 

[sm1ke]

The feeling is mutual. Just as I thought...you're no one but a commenter trying to tell others what they can do. Take care!

Just a heads up for anyone wanting to get more info on the OP's situation. They've actually been permanently banned (by another moderator/admin) for ignoring warnings, insulting members, and being confrontational and condescending.

At least they were able to take something away from this whole thing (learning how to disable radar cruise control). Would have been nice to figure out exactly what happened to cause the issue they had though.

Thanks to all the members for trying to keep the conversation on topic and steer the OP in the right direction.

 

[wlong01]

I knew from the first couple posts that this was not going to end well.

 

[GFrosty]

We're all commenters trying to tell others what they can or can't do, aren't we? You presented a situation and we are telling you what you can or you can't do, but it's up to you to do it, it's not mandatory. Keep in mind that most of us here are just simple Mazda drivers, we're not Mazda gurus. We share from our experience so others, like you and me, and everybody here, can apply and take advantage of what we, as a whole, know or learnt about this car. And save some bucks in the end. Ideally.

Pretty simple, really, to take posts, queries and suggestions in the spirit they are given. Doesn't take much to not get one's "back up", over the posts of others.

Civility. Much underrated until it's sharply abused. Leaps of assumption and refusal to take queries in the spirit given can be deadly to learning, conversation.

Kudos to those who have tried to keep this one on track.

 

[SparkYellow]

For me it was the mentioning of a certified letter to the GM. Nowadays people just threaten legal action openly, no need to use certified mail. Like it's ok to break up by text, no need for an eloquent dear-John letter.

Before things went south I was reading up on how MRCC works and why braking can be abrupt in some instances (phantom braking). There are also reasons why engines stall after abrupt braking.

Mazda CX-50 and CX-90 Radar Cruise Control - Class Action Investigation | Sauder Schelkopf

SummarySauder Schelkopf is investigating a potential class action lawsuit against Mazda related to allegations that the radar cruise control system (often referred to as the MRCC) on 2023-2024 Mazda CX-50 and CX-90 vehicles is defective. Sauder Schelkopf is investigating a potential class action...

sauderschelkopf.com

Why Does My Car Turn Off When I Brake? Fixes & Tips

Car turns off while braking? Explore common issues and fixes to keep your engine running strong when you stop.

urbsgarage.com

Search terms: Mazda "radar cruise control" braking stall

AI is tricky and does not return the same results if the terms are slightly different.

 

[N7turbo]

There are also reasons why engines stall after abrupt braking.

I have not experienced that in any car in the last 20 years (except for when a battery is bad) and it only occurs when sudden braking causes engine RPM to dive below idle speeds (car is nearly stopped). I don't think that's happening on the highway due to braking; the drive wheels are still turning the engine.

So the context is important here: I don't think that article you linked is talking about stalling at highway speeds.

 

[SparkYellow]

I have not experienced that in any car in the last 20 years (except for when a battery is bad) and it only occurs when sudden braking causes engine RPM to dive below idle speeds (car is nearly stopped). I don't think that's happening on the highway due to braking; the drive wheels are still turning the engine.

So the context is important here: I don't think that article you linked is talking about stalling at highway speeds.

Thank you for pointing that out! I have only experienced stalling at low speeds due to electrical reasons. The OP described stalling after sudden braking. I thought the braking already brought the speed down before he finally stalled.

I am interested in understanding this issue but have no relevant experience to draw from. I don't have the radar, never use cruise control, and drive in M mode 100% of the time.

 

[N7turbo]

Thank you for pointing that out! I have only experienced stalling at low speeds due to electrical reasons. The OP described stalling after sudden braking. I thought the braking already brought the speed down before he finally stalled.

Thinking further, it does raise the question of whether his car stalled when it came to a stop. That would line up with the statement that he only noticed it after he came to a stop. In my opinion, that is much more plausible than stalling at highway speed.

 

[SparkYellow]

Thinking further, it does raise the question of whether his car stalled when it came to a stop. That would line up with the statement that he only noticed it after he came to a stop. In my opinion, that is much more plausible than stalling at highway speed.

The thread was titled as stalling at high speed, but the incident started with braking while on MRCC. I am questioning his choice of words. Not sure how much braking the system applies under those circumstances. It seems that there are two problems.