engine jolting/jerking when idle when aircon is on

[henrytad]

hey everyone, my car has had this problem for at least a year now and it keeps getting worse and no mechanic has been able to figure it out.
whenever I turn my AC on, 5 minutes later my engine starts to shake/jolt/jerk approximately every 2 secs while it is idle, it is so bad the entire car shakes and it feels like the engine is about to switch off.
has anybody had this problem? anyone suggest what it is?

I had my spark plugs and fuel filter changed last week so they are definitely not the problem

 

[Hrd455]

iac sensor


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[henrytad]

iac sensor


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what makes u say that? have u experienced it before? only because its doing my head in so bad

 

[Hrd455]

Because once ur ac is on it puts more load onto the engine so the iac sensor adjusts it so it wont stall


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[henrytad]

It's started doing it even when the ac isn't on now, could it still be the iac or should I be looking at something else?

 

[adamcawood]

Is it missing ? Could it be running on 5 cylinders what car is it ? Maybe try unplugging a lead or coil pack one at a time and see what happenes...
How dose it drive is it laking power or using a lot of fule

 

[Hrd455]

Have u checked the volts yet, theres a volt gauge in the dash, maybe ur alternator is dying


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[henrytad]

It can't be missing because I had my mechanic inspect it. Alternator is fine, changed it 6 months ago, it is the police pack one, voltage is constantly at 14 volt

 

[99notout]

Crap in the injector filters, or gum in the nozzles if you have done the plugs AND coils. If not replace the coils, just do all six and be done with it! Most likely a dodgy coil.

 

[Nut Kracker]

Imo I'd say the Idle Air Control valve is shot as well.
It may have been on the way out before, but has finally gone now.

Don't go cleaning it, as you shouldn't put any cleaners in it because it can damage the stepper motor.
Just get a new one: Go aftermarket, it's cheaper. Around $40 from Repco.

If you notice when the A/C is switched on, the compressor doesn't engage straight away.
This is because the ECU/PCM activates the IAC first to alleviate the extra load on the engine caused by the compressor.
If the IAC is faulty, it can't compensate for that extra load and the engine struggles to maintain a proper idle.