Baffled By Idle

[Chop 'N' Join]

Hi

I am completely baffled by the idle speed on my car.

I have a 380SEC - 1983 UK Version.

When it is first started from cold, the idle speed is about 1400-1500RPM for a few seconds.

It is idling at about 1000RPM when the engine is at running temperature.

Any ideas?

Thank you for any help you can give.

 

[TVRTASMIN]

Most cars will idle higher when started from cold as the coolant temp sensor will automatically instruct the ECU to richen the mixture.
When the engine thinks it is warm enough the revs will drop.

 

[Parrot of Doom]

My Rover V8 engined Tiv used to do exactly the same thing. Quite normal.

 

[Chop 'N' Join]

Most cars will idle higher when started from cold as the coolant temp sensor will automatically instruct the ECU to richen the mixture.
When the engine thinks it is warm enough the revs will drop.

Hi
That's true.
Except the correct idle speed should be around 700RPM.
It stays at 1000RPM when engine is hot.
There is obviously something wrong that it keeping it at this high idle.
Thank you for your input

 

[Stevie A]

Maybe someone has adjusted up the idle.

 

[Chop 'N' Join]

Hi
You can't adjust up the idle.
It is totally electronicaly controlled.
Any other ideas?

 

[Parrot of Doom]

Possible air leak?

 

[C220GJS]

Agree,possibly an air leak. Check all your vacuum hoses for cracking as they will be brittle on a car that age.

 

[Stevie A]

Can the throttle cable not be adjusted to increase the idle? It was just a thought.

 

[Chop 'N' Join]

Hi
Can't find any air leaks.
Used a stethoscope, found no leaks.
Tried spraying all the vacuum hoses and injectors with WD40 while the engine is idling to see if idle speed drops, nothing.
What next ?