Rodeo over 50 mph !!

[theonionma]

Hi Y'all,
I have a 1.3 SLX (K11) that behaves itself perfectly up to speeds of 50 MPH. Below 50 it pulls well, doesn't stutter or hesitate and it has a good regular tickover too. But beyond 50mph it's like a bucking bronco !! If I let the speed drop to below 50, everything returns to normal?? The poor old thing has done 98000 miles but before I begin the costly process of replacing things - can anybody suggest a good place to start??

 

[Craig]

Does the engine make the car kangaroo, or does it swerve all over the plavce?
Craig

 

[theonionma]

Hi Craig, thanks for the reply. It's an engine problem, above 50MPH it feels as if it's completely loosing power regardless of the amount of throttle I'm using. When the engine starts missing, the road speed drops below 50, everthing returns to normal. If I continue to try to achieve 50MPH+ the whole cycle starts again (hence the Rodeo reference). So I'm forced to drive below 50 which of course means no motorway driving until I can solve the problem !!?!??!!
Thanks again.

 

[Igloo]

If you drive in another gear at the same RPM does it happen?

 

[Craig]

Most likely the throttlebody - does it rev frely to the redline in lower gears?