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Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 21617
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Volvo v70 starts ok at 10deg c but starts rough at lower temperatures,

Resolved Question:

Volvo v70 starts ok at 10deg c but starts rough at lower temperatures, injectors have been
removed and checked out ok, all glow plugs are ok, this is a D5 2.4 diesel engine. The engine runs very well on the road, also noticed cooling fans running when engine not very hot, what do you think?
Submitted: 1 year ago.
Category: Car
Expert:  Matt replied 1 year ago.
Hello for the cooling fans to be on and the rough running that you have then its likely that the engine coolant sensor is faulty this is located very close to where the top hose from the radiator returns to the engineits a simple 2 wire sensor that screws into the thermostat housing so I'd replace this
Customer: replied 1 year ago.
ok so do you think the coolant sensor is affecting fuel metering when the engine is cold
Expert:  Matt replied 1 year ago.
yes that's it exactlythe ECU uses the coolant temp sensor to control the fueling for cold starts, if faulty then this can skew the air fuel ratio from what is required
Expert:  Matt replied 1 year ago.
do you still need help?
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Customer: replied 1 year ago.
Thanks for that Matt, have got a temp sender/thermostat unit in housing (thought it best to stick Volvo genuine parts with this problem) that's how Volvo supply them now, if I'm able to use this communication later, will let you know if problem solved having fitted above part, have a nice day.
Expert:  Matt replied 1 year ago.
Customer: replied 1 year ago.
Matt having changed the temperature/thermostat housing complete the cooling fans are still running with engine cool, don't know yet if engine runs any better when cold.
regards Malcolm
Expert:  Matt replied 1 year ago.
Ok in that case I'd check the condition of the fan control unit on the back of the fan cowling
the fans are powered via this unit and if they are running all the time its likely that the unit is fused or otherwise damaged
so check the unit for signs of overheating and or corrosion
Customer: replied 1 year ago.
ok thanks for info
Customer: replied 1 year ago.
Hi Matt with regard to D5 rough starting, when air con is turned off the cooling fans stop and run when turned on irrespective of the temperature, apparently this is normal, regarding starting cold the rough running has been cured cold mornings & evenings tested this, thanks again for the info
Expert:  Matt replied 1 year ago.
glad to help

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