Problem with intermittent power reduction

[Euan]

Hi there,
We have had our MG4 SE SR for over a year now and love it. Unfortunately we have experienced a problem since its first annual service last December (this included a software update). The car runs fine on short journeys but on longer journeys it occasionally reduces power for a few minutes, limiting the speed to less than 30mph and preventing any acceleration. It then recovers and drives normally. The dealer tested the car and initially could find no problem but eventually decided to replace a power controller. We got the car back in Jan and it ran fine until this weekend when the problem recurred. The car is now back with the dealer. Each time the problem has occurred the battery was more than 50% charged.

Has anyone experienced the same problem and found a solution? Thanks for any help you can give

 

[siteguru]

It sounds like a variation of the power loss issue, but I don't recall anyone else describing these specific symptoms. It'll either be a hardware or software issue so only your dealer can handle this.

I recommend (if you have a passenger when this issue occurs) that you get then to video the driver display when it is happening - it'll help to record the issue and provide feedback for the dealer to supply to MG.

 

[Rolfe]

This is the thread that has all the info on what may be the same problem. It's very long as it was quite a saga.

MG4 Restricted speed - weird

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...

www.mgevs.com

A couple of people whose cars had it from new rejected their cars. Then in about July/August last year it seemed that it had been cured by a software update. Several people reporting that their cars were absolutely fine after that.

Nevertheless there has been at least one person who claimed the software update didn't cure the fault, and there have been occasional intermittent reports of it occurring again, either in new cars or (like you) after a software update.

I think you need to get as much evidence as you can, in case your dealer says he can't replicate the fault, and then take it up with him.

 

[K15DNS]

My MG has been in the garage since 22nd Jan with simular issue, it went into the garage before this for the battery not holding charge, they said this was sorted and they had done an update which then caused the issue with loss of power and refusing to go over 40 mph. Spoken to them Friday 16th Feb they stated they have no idea what the problem is and they are waiting for MG to contact them.
Really not happy with my car now

 

[yodu45]

For me, mg4 trophy v1, no update since may 2022. I had this problem about 2 times, after 50 km or so, and in warm weather. My guess is something is too hot (bms perhaps) and the car is restricting power.

 

[yodu45]

For me it was like losing some horsepower, not a speed limit.

 

[Tuareg]

For me, mg4 trophy v1, no update since may 2022. I had this problem about 2 times, after 50 km or so, and in warm weather. My guess is something is too hot (bms perhaps) and the car is restricting power.

Why no update since May 2022, nearly 2 years ago. Surely you can get the software updated at the annual service?

 

[yodu45]

May 2023, my bad. the annual service in 2 months.

 

[tsedge]

Note that there are two different problems being discussed here:

1. Fault with the SR cars whereby there is an arbitrary speed limit imposed by the car (cannot exceed it). This is the issue Rolfe highlights with the Bowfer thread.

2. A power restriction on cars whereby the power is limited but not the speed per se.

These are two different things and there's no evidence they are connected.

There are a number of software updates to address problems in this area.

 

[Rolfe]

Are you sure? I thought Bowfer was also talking about restricted power. But if there are two different issues it would explain why some updates work for some cars but not for others.

 

[richlove]

I understood these to be the same issues (having experienced both, and still have them)

 

[Euan]

Thanks for all this feedback. We will see what the dealer and MG have to say. The issue has knocked our confidence in the car. If it happens again we will try to get a video of the driver display.

 

[tsedge]

Are you sure? I thought Bowfer was also talking about restricted power. But if there are two different issues it would explain why some updates work for some cars but not for others.

Some people could have both and even on the Bowfer thread there were a number of people with the power restrictions not the speed limit.

And we have seen power restrictions on LR cars, especially the XPower. I haven't seen the speed limit reported on a LR car.

I think the fact that there are multiple issues is why some people are having this issue solved by dealer updates and others not.

 

[tsedge]

I understood these to be the same issues (having experienced both, and still have them)

I believe they must be separate since some people have only one and you must be unlucky to have both.

 

[richlove]

I believe they must be separate since some people have only one and you must be unlucky to have both.

I think what confused me is that point 2 is what seemed to occur to my SR, and struck me as the main issue with SR cars, though you mention that in point 1. Not trying to be pedantic, though would be good to paint a clear picture for folk.

Mine was definitely a power restriction issue, which often manifested as a speed restriction issue on fairly consistent road/gradient.

 

[tsedge]

I think what confused me is that point 2 is what seemed to occur to my SR, and struck me as the main issue with SR cars, though you mention that in point 1. Not trying to be pedantic, though would be good to paint a clear picture for folk.

Mine was definitely a power restriction issue, which often manifested as a speed restriction issue on fairly consistent road/gradient.

Understood, yes a power limit is effectively a speed limit on a given gradient.

But the Bowfer thread problem was about a hard speed limit irrespective of power level - ie power reducing to maintain a hard limit. With the limit itself not being consistent from journey to journey when it appears.

This was considered particularly alarming and potentially dangerous if on a fast road.

 

[Euan]

Hi again, We have just picked up our car from the dealers. No problems driving it home. The mechanic did find it "sluggish" when first tested and decided to update "the software for the rear motor". He retested it and it drove well. Let's hope the problem does not recur. Will try to get photo/video of driver display if it does.

 

[LadyCyberRosie]

My MG has been in the garage since 22nd Jan with simular issue, it went into the garage before this for the battery not holding charge, they said this was sorted and they had done an update which then caused the issue with loss of power and refusing to go over 40 mph. Spoken to them Friday 16th Feb they stated they have no idea what the problem is and they are waiting for MG to contact them.
Really not happy with my car now

I have had similar charging issues and then this has happened today with power limited to 50 miles an hour whilst on the motorway. Nearly had a panic attack whilst driving with lorries beeping at me. Trying to get my car into the garage now - it came back to me a week ago having had multiple updates after charging issues and now this.

 

[Rolfe]

Oh no! How long have you had the car?

 

[tsedge]

I have had similar charging issues and then this has happened today with power limited to 50 miles an hour whilst on the motorway. Nearly had a panic attack whilst driving with lorries beeping at me. Trying to get my car into the garage now - it came back to me a week ago having had multiple updates after charging issues and now this.

This sounds like a speed limit not a power limit.

There have been two different issues in this area:

• Power limit: power percentage is limited but the speed is not so the max speed depends on terrain, hills etc...
• Speed limit: the car will not go faster than a set speed and power varies to match whatever this speed is (the limit varies).

Which did you experience?