Feels like a speed limiter

[PK_Nuts]

Hey guys my mother is having a problem with her Corsa 1.2 sxi and we can't work out what the problem is. When you get to around 70 on the motorway the car seems to hit a wall and starts to slow down and the engine management light comes on and the car decelerates. When you drops down to 40/50 the light goes off and the car can then speed up again. Now that's a long standing problem but recently the car has also starting chugging on take off when cold. It sound's like it's running on three when cold and will cut out as the revs drop. Which is pretty dangerous for her when taking off out of our road.

Anyone have any ideas?

Thanks

[johnny]

Plenty of ideas but I'd get the codes read first before you start buying sensors

[coupe77]

Get the codes read first
As a guess I would say cam or crank sensor


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[williamt73]

It is the MAF. I had exactly the same problem on a 2000 SXi. 3500 revs = 70 in top gear.
Codes will tell you it is the O2 sensor. Wrong.
Prove it by doing a disconnect test. Disconnect the wiring to the MAF. Warning light will be on, but ignore that. Car will now get happily above 3500 revs (70mph). Plug it back in & problem will reappear.
Do not replace it with one from ebay. They are a false economy. Find a proper Bosch or GM replacement.