Cold start - Auto choke?

mikesmith20001 · Post by **mikesmith20001** » 20 Jan 2011, 05:37

Hello,

Year: 2006
Miles: 106k kilometers or 66k miles
Repairs: Fuel pump and fuel computer module about 7 months ago
Location: Canada

My 2006 AWD 2.5LPT S80 seems to be having problems starting when its goes -15 or below. It turns and starts fine, but the engine goes to idle as though it was warm - sub 1k revs, so the car starts to run rough. I switch off and turn on again and like normal the engine goes to 2k revs and brings itself down slowly and all is fine.

I had this problem on an old car (ford) of mine and it was a faulty auto coke, but not sure what controls the "choke" aspect of modern engines.

Any ideas on what to check?

Car is maintatinend by Volvo dealer due to warranty, its up to date with all services.

Thanks,

Post by **jimmy57** » 20 Jan 2011, 08:39

The "auto choke" is actually the fuel injection computer monitoring coolant temp and giving the right fuel and controlling idle speed to higher level proportionately as starting temp is colder and colder.
IS the battery the original in that car?
The functions of the fuel computer for starting can be a bit wrong for starting if the battery is weak.
Getting battery checked can be done at a Canadian Tire or other service outlet like that with little or no wait usually.

mikesmith20001 · Post by **mikesmith20001** » 20 Jan 2011, 13:34

Thanks Jimmy57.

Yes the battery is the original in the car.

I will get the battery checked.

Can i just do this myself with a multi meter? Save me having to drive around and i'm also really picky who i let work on the car.

Post by **jimmy57** » 20 Jan 2011, 14:24

It is less accurate but probably gives a valid answer to whether it is time to get a battery.
First attach your MM to ground and the stud you find under the flip up cover immediately behind the fusebox in engine compartment.
Start the engine and see what voltage the charging system is doing. 13.9-14.4 DC V at first and it will fall a little with time and if the engine is warmed up from driving already the range may be a bit less. Then switch the meter to AC V and see that it is less than 50 mV (0.05V) AC. Right charging voltage can be there when the alternator has a faulty diode and will not keep the battery up, a diode failure will give excessive AC voltage. Not THE test but a good enough one to decide whether charging system needs investigation.
Now switch off ignition and let the car stand over night with hood unlatched and if it is in garage the voltmeter can stay put.
In the AM check the voltage without doing anything but raising the hood that was already unlatched. If you do anything that triggers any functionality on that car it will switch on network and the voltage will be lower for that reason and not give a valid test. Rest battery voltage is a decent indicator of battery health. The battery should have had a period of no charging and also no real loads. Also the battery must not have a "surface charge" but the current draw after key off that the networked Volvos have is enough to take care of surface charge issues. Surface charge is an artificial high voltage that a battery will have from being charged.
At 20 C a good battery will have 12.5 or better in this test. 0 C should have 12.3, if it is colder than that then a little lower V.