another m20 idle issue

[bmwrp8]

when I start my car every morning or when the engine is cold first start RPM reaches 1500 to 1700 RPM then after a few minutes (yes minutes!) goes down to normal 750 rpm. Is this normal?didn't have this before...I disconnected the plug of the ICV to see if it changes but it did not. any ideas?

[E34-520iSE]

when I start my car every morning or when the engine is cold first start RPM reaches 1500 to 1700 RPM then after a few minutes (yes minutes!) goes down to normal 750 rpm. Is this normal?didn't have this before...I disconnected the plug of the ICV to see if it changes but it did not. any ideas?

You can relax - the fast idle when cold is normal. The ECU takes a reading from the blue temp sensor on the thermostat housing and decides whether to enrich the mixture. Once the ECU is happy that the coolant is warm enough it will allow the mixture to return to standard, which drops the RPM's and makes the engine sound and run smoothly once again. Any problems with the idle control system will be down to a failed blue temp sensor, a stuck ICV or a vacuum leak.

HTH,

Shaun M

[EngPhys09]

Could it have anything to do with the idle control valve?

[timandbim]

i had the opposite problem (low rpms at startup) this summer. once the engine got a tiny bit warm, idle would go normal. the revs are supposed to increase if you disconnect the icv plug with the motor running, so if this doesn't happen for you i bet your icv or your connection is bad... but really i don't know much other than replacing the icv with a used one worked like a charm for me and i have an m20. my 'new' icv makes a very noticable high-pitched hum, like the book says it's supposed to.

[bmwrp8]

You can relax - the fast idle when cold is normal. The ECU takes a reading from the blue temp sensor on the thermostat housing and decides whether to enrich the mixture. Once the ECU is happy that the coolant is warm enough it will allow the mixture to return to standard, which drops the RPM's and makes the engine sound and run smoothly once again. Any problems with the idle control system will be down to a failed blue temp sensor, a stuck ICV or a vacuum leak.

HTH,

Shaun M

hmm funny before it doesn't seem to do this

[bmwrp8]

Could it have anything to do with the idle control valve?

guess not.. I removed it and still is the same

[E34-520iSE]

How long have you had the car for BMWRP8? I remember that by disconnecting the blue temp sensor also tricks the car into doing a warm start. The only trouble is, this makes the car difficult to start when warmed up for some reason. As you're having no start-up issues I can only assume that all is well - it sounds like your idle system is working properly - high idle when cold, normal idle when warm.

HTH,

Shaun M

[bmwrp8]

How long have you had the car for BMWRP8? I remember that by disconnecting the blue temp sensor also tricks the car into doing a warm start. The only trouble is, this makes the car difficult to start when warmed up for some reason. As you're having no start-up issues I can only assume that all is well - it sounds like your idle system is working properly - high idle when cold, normal idle when warm.

HTH,

Shaun M

had the car around 2years