Hi,

All winter car been awesome while driving. But as soon the summer is getting up heat, while on idle or in D, Car's RPM starts fluctuates and stops the car. No code at all and dash is clean. Any ideas what could be the culprit.

Regards,

 

Check your MAF is functioning okay.
Unplug it and see how the motor runs then. If no change then it is discounted.
The IAT sensor determines the engines inlet air temperature and the fuel/air mix is adjusted to suit. If faulty that can lead to mixture being to lean or rich.

Iat Sensor Location? - Ask.com


Is your air filter clean?

 

Thanks Difflock, MAF is OK when checked as you suggested.

Can you confirm me where is the location of IAT in my engine (Its Volvo s80 1999 2.9 non turbo).

Plus why it gives me problem only summer or if the temperature is over 35 C. No problem at all when the temperature is less than 30 C.

Thanks.

 

The IAT is incorporated in the MAF unit on non turbo.
See diagram in this link below.

http://www.justanswer.com/volvo/3ol9...re-trying.html

Could be as simple as a loose wire or dirty connection.
Check before outlaying on a new sensor.

The coolant temp' sensor can also cause engine to run roughly but that sometimes turns out to be the thermostat sticking.
The coolant temp' sensor is located alongside or incorporated in the thermostat housing.

 

Hi difflock,

The picture shown in link does not same as my engine. It is without upper engine air hoses and...I forget to say my AIR Filter is new....but I will surly try to clean the coolant temp' sensor dirty connection. By the way, engine runs smooth only RPM Fluctuate up and down when outside temp over 35 C and when I am standing on signal.