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Volvo V70 hunting when aircon on

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  • 16-06-2006 4:34pm
    #1
    2002
    Registered Users Posts: 9 ✭


    Hi,

    My Volvo V70 idle engine speed hunts whenever the aircon is on. By hunts I mean the engine speed fluctuates up and down a few hundred rpm. It seems to go up and down as the aircon compressor cuts in and out. When the aircon is off the engine idles perfectly.

    Any suggestions on this problem would be appreciated.

    Thanks.


Comments

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    #2
    mike65
    Closed Accounts Posts: 88,978 ✭✭✭✭mike65


    Hows your alternator? Is the battery light showing at all?

    Mike.


  • Options
    #3
    johndoe77ie
    Registered Users Posts: 269 ✭✭johndoe77ie


    Could be a problem with the ETM. Have a look here.
    www.vexedvolvo.org


  • Options
    #4
    mike65
    Closed Accounts Posts: 88,978 ✭✭✭✭mike65


    May have found the problem

    http://www.startribune.com/131/story/34776.html
    Q. I am having an idle issue with my 2000 Durango. It sometimes surges and fluctuates about 200 to 500 rpm at idle. At other times, the idle is stable but seems a bit high at 1,000 rpm. When driving, the engine rpm seems to fluctuate and surge a bit and confuses the transmission. I know that the transmission is good; it shifts smoothly and feels tight. Is this a tune-up issue? A. These are classic symptoms of a vacuum leak in the induction system. Whether the leak is from the throttle body or intake manifold gasket, or from a vacuum hose, port or device, extra air entering the induction system is not "metered" by the engine management system. This creates a slightly lean condition, which typically causes an unstable or slightly high idle. In many cases, the only time a small vacuum leak is noticeable is at idle: The extra air from the leak is a higher percentage of the total air entering the engine at idle than it is when the throttle is open and the engine is using more air and producing more power while under load. Many shops have a machine that finds vacuum leaks by using a nontoxic smoke. With the engine shut down, smoke is introduced under light pressure through a vacuum port, and the technician watches for where the smoke might be escaping from the engine: That's the source of the vacuum leak. Another possibility might be faulty or sticky IAC - idle air control motor - mounted on the throttle body. The IAC is a small electrical stepper motor that varies the idle air opening based on a signal from the engine management computer. If the motor is sticky or the orifice is clogged with carbon, it might not provide the exact amount of idle air commanded by the computer

    When the air-con is running the engine is under greater load.

    Mike


  • Options
    #5
    2002
    Registered Users Posts: 9 ✭2002


    Thanks for the responses.

    1. Alternator is ok and battery light is not showng up.

    2. ETM - very intersting - indeed this could be the problem.

    3. Vacuum leak in the induction system - also looks like possible cause.

    My local mechanic had a look at it today and connected his computer to the engine management computer but there were no faults - he is going to call a local Volvo dealer to see what they say - I'll pass on these suggestions to him on Monday.

    Thanks again.


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