MG4 Restricted speed - weird

bowfer said:
Big shot in the dark that anyone else has experienced this, but worth a go.
My drive home involves a short blast up a dual carriageway from a set of lights, bit of a Grand Prix to be honest.
Twice now I’ve floored the car up it and it’s resolutely refused to do more than 71-75mph.
It’s not a power thing, my Leaf with less power would do a lot more.
But, foot to the floor, 71mph (ish) !?!?
I also noticed that when I pulled off the main dual carriageway onto a slip road, it started accelerating again….
Naturally I suspected I’d inadvertently triggered some speed limiter thing, but I checked that and it was fine.
Cruise is off too.
Very weird….
Click to expand...
I've just had a similar issue, but loss of power seems to be under load i.e. Driving up hill. I had an alert with a slightly low tyre pressure at the time. Waiting to see if the issue now clears
 
This happened to me after doing 25 miles in my new car.

While on the motorway the car went into power restricted mode and wouldn't allow me to accelerate on a flat road above 20MPH.

After over 4hrs AA said they couldn't fix it and I would need recovery. 4hrs later the car was operating normally again so I proceeded to drive to the dealer which due to been on the wrong said of the motorway was now 34 miles away. After about 20 miles of normal driving and using just A roads it happened again. I limped it back to the dealer and await what they say when I get a lift there in a few hours.

Things to note so Far.

Spoke to the dealer on the roadside as the battery when I picked it up was only at 78%, he said it was fully charged 2 days ago? The car when I picked it up had 9 miles on the clock. Alarm bells started to ring lol.

To drive the 25 miles it dropped the battery charge level from 78% to 38%. Again alarm bells.

I'm guessing due to the power limiting, the heating doesn't work when the fault is active as I had no heating.

The AA put the computer on the car and there was no faults.

Anyone else had this problem.
 
tsedge said:
Is this an SR or LR? If SR, when was the last time you did a 100% charge?

If you've done one within the last week (so battery is balanced) or have LR and the battery had had time to warm up then sounds like the car is restricting the power to protect the battery or motor: could be a bug or a temporary problem with the battery state, or the motor was overheating (unlikely unless you were driving like Lewis Hamilton).
Click to expand...
SR.
I'd carried out a full charge later weekend and a couple of top ups during the week.
I dont think the motor would have been over heating .It was -3 and hadn't been ragging it .
There was no battery warnings.
 
tsedge said:
Hmmm.. if clicking the mode helps, suggests this is software enforced. The car thinks it needs to back off power. Any chance you'd overheated the motor?
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No it had been a gentle drive,

A message did pop up on the screen for a second (Driver Screen), Something about Eco Enforced and then Eco Overridden due to power applied. But did not get to see it clearly as it was on and off so quick and I was caught out by the change in power.

Vicky actually said for a few seconds before it happened she thought the car was juddering like a petrol car that was starved of fuel but I cant say I felt that.
 
Stageshoot said:
No it had been a gentle drive,

A message did pop up on the screen for a second (Driver Screen), Something about Eco Enforced and then Eco Overridden due to power applied. But did not get to see it clearly as it was on and off so quick and I was caught out by the change in power.

Vicky actually said for a few seconds before it happened she thought the car was juddering like a petrol car that was starved of fuel but I cant say I felt that.
Click to expand...
SR or LR?
 
Stageshoot said:
No it had been a gentle drive,

A message did pop up on the screen for a second (Driver Screen), Something about Eco Enforced and then Eco Overridden due to power applied. But did not get to see it clearly as it was on and off so quick and I was caught out by the change in power.

Vicky actually said for a few seconds before it happened she thought the car was juddering like a petrol car that was starved of fuel but I cant say I felt that.
Click to expand...

Yup, that’s one indication I get that the speed restriction is coming.
Any acceleration is ‘lumpy’ like an ICE car misfiring.
Lumpy and slower than optimal acceleration, then a guessing game as to what top speed I’m going to get this time (has so far varied from 70mph down to 50mph)
 
My best guess is that this a bug in the battery system. If it were confined to SR models that would make sense as LFP battery is new and LFP BMS is harder to get right. However, if LR models are also suffering the same result, probably a wider bug.
 
This may not be for everyone but if your are stuck, disconnecting the 12v battery (take off the negative terminal) and reconnecting after about 30secs can, in a lot of cases reset things and you may be able to continue on your journey. It’s a common practice on broken down EV’s.
Of course it doesn’t cure the root cause, but might get you home.
I think a 10mm spanner and pair of pliers kept in the car is worthwhile if you’re up for it, and might just get you out of a hole. It can also work with charging issues…
 
Stageshoot said:
No it had been a gentle drive,

A message did pop up on the screen for a second (Driver Screen), Something about Eco Enforced and then Eco Overridden due to power applied. But did not get to see it clearly as it was on and off so quick and I was caught out by the change in power.

Vicky actually said for a few seconds before it happened she thought the car was juddering like a petrol car that was starved of fuel but I cant say I felt that.
Click to expand...
My understanding is forced eco is turtle mode when the battery is reporting exceptionally low voltage which to me indicates a BMS issue, do you regularly balance your battery?
 
Ayoull said:
My understanding is forced eco is turtle mode when the battery is reporting exceptionally low voltage which to me indicates a BMS issue, do you regularly balance your battery?
Click to expand...
I charge to 100% every night as we use the full range of the car almost every day, so yes it gets regular balances.

And the Turtle light that comes on at very low soc was not on..
 
Stageshoot said:
I charge to 100% every night as we use the full range of the car almost every day, so yes it gets regular balances.

And the Turtle light that comes on at very low soc was not on..
Click to expand...

Cocijo said:
This may not be for everyone but if your are stuck, disconnecting the 12v battery (take off the negative terminal) and reconnecting after about 30secs can, in a lot of cases reset things and you may be able to continue on your journey. It’s a common practice on broken down EV’s.
Of course it doesn’t cure the root cause, but might get you home.
I think a 10mm spanner and pair of pliers kept in the car is worthwhile if you’re up for it, and might just get you out of a hole. It can also work with charging issues…
Click to expand...
Would it be worth doing a factory restore do you think?
I'm granny charging fro the next 6hrs or so but have to go out tonight.
 
Do no harm to at least try it. Are you capable of disconnecting and reconnecting 12v battery as another possible step?

This is all sticking plasters in reality until MG get to the bottom of it
 
NickHeynes said:
Would it be worth doing a factory restore do you think?
I'm granny charging fro the next 6hrs or so but have to go out tonight.
Click to expand...
I agree with the briggie. It would do no harm and might even cure it. A bit like Windows asking you to reboot your laptop after an update so the registry can be updated.
 

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