My S60 is surging/hunting at idle between 700rpm and 1000rpm. It is
more pronounced when the a/c is switched on. I'm thinking Mass Flow
sensor.

I changed the plugs today with no change in performance.

I have an OBDII reader. There are no faults appearing on the message
display on the dashboard.

The car runs just fine, I can pull 6000rpm through the gears no
problem.

Any suggestions?

Regards Chris.

mcbrien410 (AT) aol (DOT) com wrote:

I would start by cleaning the throttle body and if it has one, idle air
valve. This stuff tends to get gummed up from oil vapors out of the
crankcase vent system, mileage is about right for that.

Air mass meter normally causes much more pronounced problems when it
acts up.

<mcbrien410 (AT) aol (DOT) com> wrote

No, more likely to be the ETM, very very very very common on the early
Marelli units. There is a dealer software update and clean which helps, but
the unit is on its last legs and will need changing to the much more
reliable Bosch ones. This again requires new software in the ecu.

If the idle isnt too bad with the a/c off, but worse with it on, then
definately the etm.

Google Volvo ETM.

Tim.

On 8/9/2009 2:32 PM, mcbrien410 (AT) aol (DOT) com wrote:
have them perform Recall # 155 ETM Software Upgrade if this was already
performed the ETM may be very dirty which is caused by the breather box
being clogged partially or totally the dealer will be able to correctly
diagnose this for you as for no codes the obd reader will not read the
ETM for some reason if the ETM is faulty it is under the 10 Year 200K
Extended Warranty but the ETM cleaning is not part of the extended
warranty & is the breather box if it is determined that these are the
problems almost always it is an internal fault in the throttle unit but
Volvo requires that the ETM be cleaned first before replacement
G Klein
Volvo Certified Technician 2008
ASE Certified Technician 2008