Constant Speed - Hunting......

[mikejgeo]

2002 9-5 Aero
When at a constant motorway speed, either manually or on cruise control, the engine can be felt to 'hunt' up and down, the RPM does not change but you can see the boost change on its gauge.
This is not new but probably has been happening for a year.
CPS changed recently.
Anyone any ideas?
Want to drive it through France this year so probably need to get to the bottom of this.

Mike

[Steve440]

Hunting is usually caused by a lean mixture, most modern cars go lean when on cruise to save fuel but it sounds like yours is go to lean.

The most obvious would be either an air leak or a faulty lambda sensor or even both.

If you buy a plug in code reader a lot will give you live data so you can see what is happening. Well worth £50 and useful if an engine warning light comes on.

Dont start guessing and putting parts on, this can cost lots of £'s and is often not the correct part.

Steve