1999 s40 t4 won’t idle

[S40 t44]

1999 s40 t4 101k Miles won’t idle can anybody suggest the possible cause for this I have changed maf sensor idle control valve fuel filter and still won’t idle any help appreciated thanks

[gatos]

Replacing (or cleaning) the ICV would have been my first suggestion, so we can rule that out. Does the car drive ok (other than the idling)

When were the spark plugs last replaced? Did you use genuine ones or aftermarket ones? Our model and specially the T4 go much better with genuine spark plugs. What condition are the coil packs in?

It may be a silly suggestion, but how does the car idle when you unplug the MAF? Reason I am asking is because when the MAF is disconnected, the ECU runs on default values and kind of ignores the sensors. So if the car idles fine with the MAF unplugged, it could point to one of the sensors being faulty.

Ideally, if you can get your codes read, it would give you an indication of what might be causing it

[S40 t44]

Thanks for the reply gatos the spark plugs are brand new genuine Volvo ones 2 of the coils were replaced recently with non genuine parts could this potentially be the cause ? car still wouldn’t idle with the maf unplugged that just made the dsa light come on when unplugged I have fitted brand new genuine Volvo maf sensor brand new non genuine icv new fuel filter strangely today when I started the car it’s now fluctuating between 1000 1500 rpm which it hasn’t done before other than that car is driving fine I did get the codes read and they were maf sensor faulty signal front heated oxygen sensor faulty signal long term fuel trim and torque reduction any more suggestions many thanks Ryan

[martin93]

It might be worth checking for vacuum leaks. If you can get it to idle have a good listen around vacuum pipes at the front of the engine, around the throttle body area and listen for any hissing. Also pop your ear next to the brake servo and have a listen.

Martin

[S40 t44]

Thanks for the suggestion Martin I have checked for vacuum leaks and can’t hear or see any at all I read my fault codes again today after changing maf sensor and idle control valve and the only code showing now is front oxygen sensor so I am presuming it is that at fault the car is now idling high between 1000 1500 rpm has anybody heard of the oxygen sensor causing this problem thanks