C30 idle issues

[MrEgg]

Hi, I'm a C30 newbie. It's a 1.8 petrol, only 52k miles. It runs great but the idle speed stays high (1200 plus ) for a long time after start up. It eventually settles at around 850/900, but if its turned off and restarted (even after just a few minutes) the revs go back high again. When I rev to say 3000 the revs are slow to come down, sticking at 1400 ish for a second or so before quickly coming down. I've cleaned the throttle body which hasn't solved it. It's not nice to drive in traffic and the mpg is horrendous, about 27.5mpg.

Any ideas please?

[Dastardly Diesel]

Do these have an IACV?

[MrEgg]

Originally Posted by Dastardly Diesel

Do these have an IACV?

I don't think so. There's a stepper motor of some sort attached to the throttle body, but no no sign of an idle air control valve - instinct was/is that if there is one to give it a clean. It seems like that kind of issue but having cleaned the throttle body, I'm not sure where to go next!

[MrEgg]

Anyone have any ideas on what the issue is? No signs of any split pipes. Air filter and all service parts new and OK. Throttle body now clean. I can't see an IACV or MAF sensor on the engine so not sure what else it could be. Any pointers woudl be appreciated.

[Dastardly Diesel]

Originally Posted by MrEgg

I don't think so. There's a stepper motor of some sort attached to the throttle body, but no no sign of an idle air control valve - instinct was/is that if there is one to give it a clean. It seems like that kind of issue but having cleaned the throttle body, I'm not sure where to go next!

Yes, the stepper motor performs that function. If cleaning it carefully doesn't cure it then it might peeved replacing g, but I'd want to do some more diagnosis first.

[MrEgg]

Originally Posted by Dastardly Diesel

Yes, the stepper motor performs that function. If cleaning it carefully doesn't cure it then it might peeved replacing g, but I'd want to do some more diagnosis first.

Thanks. I'm not sure why I didn't clean it when I had the throttle body off. I'll take it off again and open up the stepper motor and give it a good clean. If that doesn't solve it I'll report back.

[MrEgg]

Originally Posted by Dastardly Diesel

Yes, the stepper motor performs that function. If cleaning it carefully doesn't cure it then it might peeved replacing g, but I'd want to do some more diagnosis first.

I've removed the stepper motor. Was clean as a whistle. No broken teeth and moving well. Gave it a clean anyway to make it spotless and re cleaned the already clean throttle body. It's still doing the same.

What else could it be? I can only think coolant sensor but that seems unlikely. Other option is perhaps a dealer software update?

[Kais]

Originally Posted by MrEgg

I've removed the stepper motor. Was clean as a whistle. No broken teeth and moving well. Gave it a clean anyway to make it spotless and re cleaned the already clean throttle body. It's still doing the same.

What else could it be? I can only think coolant sensor but that seems unlikely. Other option is perhaps a dealer software update?

Hi! I have the same problem with my c30 1.8.
Did you solve this issue already?

[Clan]

Originally Posted by Kais

Hi! I have the same problem with my c30 1.8.
Did you solve this issue already?

try wiggling the plug on the throttle . ANY movement at all then wrap a layer of insulating tape around the outside of the plug and refit , that should make it solid and no movement , a spray of wd 40 on the pins will clean off any fretting residue . This was a service bulletin 15 years ago

[Kais]

Originally Posted by Clan

try wiggling the plug on the throttle . ANY movement at all then wrap a layer of insulating tape around the outside of the plug and refit , that should make it solid and no movement , a spray of wd 40 on the pins will clean off any fretting residue . This was a service bulletin 15 years ago

I did it, but the problem is still here 😕