v70 engine hunting ( varying rpms ) Topic is solved

pauluscamperman · Post by **pauluscamperman** » 24 Jul 2020, 11:07

Hi my son has a 2001 v70 2.4 petrol N/A.
we've just replaced front suspension, on restarting engine runs as normal until brake leaver is depressed then the engine starts to hunt getting progressively worse until engine stalls. can't find any obvious vacuum leaks. any ideas?

Post by **jonesg** » 24 Jul 2020, 12:37

pauluscamperman wrote: ↑24 Jul 2020, 11:07 Hi my son has a 2001 v70 2.4 petrol N/A.
we've just replaced front suspension, on restarting engine runs as normal until brake leaver is depressed then the engine starts to hunt getting progressively worse until engine stalls. can't find any obvious vacuum leaks. any ideas?

On mine the vacuum is assisted by a pump that I can hear cycling on off as I start down the driveway, just a quiet hum on and off.
Its barely louder than the fuel pump. You probably wouldn't notice if it wasn't cycling by ear, but it would steal vacuum at startup..

Does it go away once the engine warms up.?

pauluscamperman · Post by **pauluscamperman** » 24 Jul 2020, 15:17

Hi, the problem remains at all engine temps

Post by **jonesg** » 25 Jul 2020, 21:30

pauluscamperman wrote: ↑24 Jul 2020, 15:17 Hi, the problem remains at all engine temps

Smoke test the vac system.
see robert diy youtube video for diy smoke tester.

pauluscamperman · Post by **pauluscamperman** » 29 Jul 2020, 02:33

HI Vac system is sound with no leaks, but seem to have resolved issue as car threw an O2 sensor code, I can't explain why the code did not come up sooner but car is now back to normal

Post by **abscate** » 29 Jul 2020, 04:50

Added to title to help those wondering how Volvo engines can run and hide