Does everyone else's cruise control "pump" on and off?
 

Hi there,

I've owned a 190 ZT-T for a little over a month now.

Do all 75s/ZTs exhibit this obvious "pumping" behaviour on cruise control where the ECU applies power for a few seconds until it's slightly over speed, then comes off the power until it's slightly under and repeats like that endlessly?

Is it just MG Rover's archaic cruise control, or is mine broken?

Thanks.

I can't say I've ever noticed that no. It doesn't sound right. On my car it's no different to the cruise on any other I've driven.

Can't speak for the zt , but my old mk1 audi A6 has cruise , but the only time you really notice it doing anything is when it applies acceleration up a hill and then cuts power on the way back down the other side.

How frequent is the 'pulsing' ?

I'm certainly familiar with that sensation in other cars. It's similar to that, but it does it on flat road, a few seconds on, a few seconds off, all the time.

It's not moving up and down by 10 mph or anything like that, it's just quite clearly going up and down between probably 69mph and 71mph every 5 or 6 seconds and you can tell when it's pulling and when it's "resting" on a continuous cycle.

Hi, I have a slightly older 75 but recently made great use of CC whilst driving to Norfolk from Scotland. Only noticed the increasing revs going up hills/reducing revs going downhill as already mentioned. No 'pumping' and it certainly made the journey very easy!! Good luck with solving your issue.

My ZTT is perfect on cruise but as others have said I have felt the sensation you are talking about on other makes of cars, it is usually on Turbo cars especially if they have been tweaked.

The worse one I had was a Saab 9000 Aero, tweaked to about 300bhp and the cruise was almost unusable, below 60mph it was acceptable but anything above that and even passengers were complaining after a few miles.

Does the Cruise get its speed input from the same source as the speedo on these cars? I know on some makes they use a different ABS Sensor for cruise than the speedo.

I believe speedo is front O/S, cruise front N/S
Someone willl correct me if that's wrong

Nige

I've not noticed mine pulsating. Mine's quite smooth.

ZT Cruise Control
 

My ZT 180 Auto has factory fitted cruise which works very smoothly with no discernible "on/off" action that you describe. I would suspect there is something not quite right with yours.

No pulsing or pumping on mine.

Just the initial boost when going up a hill to keep up to set speed. No different to the merc I had previously.