Technical warm Idle problem again.

[Migaard]

Hi Guys.

Each summer i get this weired idle problem on my 1997, 1,6 16V Marea.
When the engine reaches working temp the idle drops to around
2-300 rpm, barely able to run.

I read in the Fiat workshop manual that idle is set in 3 stages.

Start up:
Set mainly by coolant temp and battery level.

Warming up:
Set mainly by coolant temp.

Warm:
Set by rpm sensor.

I've had the butterfly valve stepper motor tested and it's working fine.
(also indicated by the engine is running fine at warm up)

I assume the rpm sensor is working since i get a correct rev read out on the dashboard.

Does anybody have any clue whats going on?
The engine idle fine at working temp in the winter...
I have measured the air intake and coolant temp sensors, they are fine.

Cheers Michael

 

[StuartH]

Sounds to me like the rpm sensor is not liking being hot.... try replacing it with a known good one from a mates/scrap car before investing though.

 

[Migaard]

Hi StuartH

Thanks for your reply
I have been thinking the same, but as far as i can see the
rpm readout on the dashboard is also given from this sensor.
The readout is OK.

I'm thinking more about the intake air temp or the MAP sensor.
In the wintertime the engine sometimes also reaches the same engine temp as in the summertime (long idle ect.)
So maybe it's depended on the intake air temp?
I've measured the intake air temp sensor and it seem to be OK.
And even if the temp sensor doesn't work the ECU should insert a recovery value which shouldn't cause this low idle.

Cheers Michael

Any hints highly appreciated.

 

[Migaard]

I was getting SO tired of the problem so i drove
to a FIAT garage, they fixed the problem within half an hour.
Even though i had the stepper motor tested earlier it was partly
defective. Now it's running like a dream

 

[01marea16v]

Glad to hear you got the problem resolved