S40 (New) General : - Erratic idle 1.8 petrol

Bailsy · Mar 8th, 2012, 21:49

I've got a 2006 S40 1.8 petrol, which runs and drives brilliantly, except for the idling. When the car is moving and put into neutral the idle drops to ~200rpm then jumps up to ~1000rpm and continues to do this (doesn't matter if clutch is up or down). But when the car is stopped the idle returns to normal (just under 800rpm) and rock steady.

The car pulls well through the gears, fuel economy good, plugs relatively new.

I have taken off the throttle body and cleaned (it was filthy), also cleaned air filter box, but made no difference. I've seen other threads which suggest the MAF sensor for this type of problem, but as far as I can tell this engine doesn't have one???

Can anyone offer any suggestions what I might try next? I have access to a code reader this weekend, but there are no warning lights on so not sure if that will help or not.

I'd be grateful of any help or ideas!!!

martin93t · Mar 9th, 2012, 10:07

I recently have had this problem but it hasn't been consistent. some days it does it and some day not at all. Doesn't make any difference if I'm petrol or gas.

So I'd be grateful for any info.

Daim · Mar 9th, 2012, 11:51

Take the throttle body out and give it a good clean up! It may look clean from the outside, but is likely to be filthy from behind. Best to get a throttle body cleaner and spray that into the intake system, whilst the engine is running. That'll clean it up nicely and the idling should return to that, what it should be.

Bailsy · Mar 9th, 2012, 13:15

Thanks Daim,

I have had the throttle body off, and cleaned it front and back. It was very dirty on the back end. But it hasn't improved!

What I can't understand is why the idle is so steady when the car is stationary, yet when the car is moving (anything above about 10mph) and in neutral the idle is so bad. I keep thinking about MAF/MAP sensor, but could be totally wrong????

Mar 8th, 2012, 21:49	#1
Bailsy New Member Last Online: Mar 23rd, 2014 11:01 Join Date: Mar 2012 Location: Bury	Erratic idle 1.8 petrol I've got a 2006 S40 1.8 petrol, which runs and drives brilliantly, except for the idling. When the car is moving and put into neutral the idle drops to ~200rpm then jumps up to ~1000rpm and continues to do this (doesn't matter if clutch is up or down). But when the car is stopped the idle returns to normal (just under 800rpm) and rock steady. The car pulls well through the gears, fuel economy good, plugs relatively new. I have taken off the throttle body and cleaned (it was filthy), also cleaned air filter box, but made no difference. I've seen other threads which suggest the MAF sensor for this type of problem, but as far as I can tell this engine doesn't have one??? Can anyone offer any suggestions what I might try next? I have access to a code reader this weekend, but there are no warning lights on so not sure if that will help or not. I'd be grateful of any help or ideas!!!

Mar 9th, 2012, 10:07	#2
martin93t Junior Member Last Online: Jun 12th, 2018 19:42 Join Date: Aug 2011 Location: Newport	I recently have had this problem but it hasn't been consistent. some days it does it and some day not at all. Doesn't make any difference if I'm petrol or gas. So I'd be grateful for any info. __________________ Volvo V50 SE port 1.8 - LPG converted. Saab 9-3ss Turbo X Saab 9-3 270bhp - track toy. Turbo lag is like foreplay, you know its coming and its going to be good

Mar 9th, 2012, 11:51	#3
Daim Brit in Germany Last Online: Jun 14th, 2024 23:09 Join Date: Jan 2011 Location: Bremen	Take the throttle body out and give it a good clean up! It may look clean from the outside, but is likely to be filthy from behind. Best to get a throttle body cleaner and spray that into the intake system, whilst the engine is running. That'll clean it up nicely and the idling should return to that, what it should be. __________________ The Best Nation Is Imagination 2010 V70 (Type 135) D5 (D5244T10) Automatic (TF-80SC)

Mar 9th, 2012, 13:15	#4
Bailsy New Member Last Online: Mar 23rd, 2014 11:01 Join Date: Mar 2012 Location: Bury	Thanks Daim, I have had the throttle body off, and cleaned it front and back. It was very dirty on the back end. But it hasn't improved! What I can't understand is why the idle is so steady when the car is stationary, yet when the car is moving (anything above about 10mph) and in neutral the idle is so bad. I keep thinking about MAF/MAP sensor, but could be totally wrong????

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)