RPM at cold start

[funthrulens]

Hello guys, I have a question, I own the car for over a year and everytime I started it up (cold start) the revs went higher for a few seconds and then go back to normal idleing. But recently it stop doing this behavior. It imediately go to normal idleing. Can this be a problem of some sensor? Or is it because I started using the 100 octane petrol?

Thanks

 

[Rudyrov]

My car does that as well, the RPM going up to maybe 2000 R's or so then dropping back to a normal idle over a period of about 1 minute.
I have always wondered if this was correct since I bought the car used. I am very curious about the responses you may receive.

 

[Zeti]

My M44 1.9 starts at 1000 RPM and after getting warmer , maybe few minutes, goes at the normal idle.
2000 RPM looks a little to high to me!

 

[funthrulens]

But mine stop doing that, that is what worries me, but when did it went to about 1300 RPM and then to 800 RPS approx.

 

[Bampz]

Could this be the way an automatic choke would operate when starting from cold , higher revs starting from cold and reducing to normal as engine warms?

 

[Rudyrov]

Given the vehicle is fuel injected it is an electronically operated choke.
A sensor would i inform the computer of the temperature and usually the idle air control will add more air to increase RPM. As the engine warms up the IAC would be instructed to rollback the air a bit to bring the RPM back down to normal.
Most issues I have seen with this system are due to dirty IAC or defective temp sensor.

 

[funthrulens]

Can you tell me where this thing is located on the 2.0 engine? thanks

 

[Rudyrov]

I wish I could, I have the 2.8 Litre engine. I'm afraid you'll have to either find a manual for your car or visit a parts house and see what it looks like. If you do find it, strat by cleaning it if you can can, what you are looking for is smooth operation of the valve and clean mating surfaces where the air passage is regulated by the valve. Some IAC's cant be cleaned and must be replaced.

 

[Lee]

My old 2.8 used to do this and still does.

Is it not the cooling loop that goes through the throttle body that controls the choke ?

I'm not 100% sure.

 

[funthrulens]

@Rudyrov ok I think I found it, I removed something, but found out later its a DISA, but this thing needs to be removed to access the IAC, so I think I'm on the right path.

@Lee I removed DISA, do you know the part number or the exact name of this choke?

Thanks

 

[funthrulens]

Its out and it was stuck I hope it will solve the issue