Volvo S40 The S40 is Volvo's most affordable sedan with all the amenities of a luxury sports car.

Have rough idle at <36°, found the problem

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Old Feb 17, 2016 | 12:44 PM
  #1  
Livens's Avatar
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Default Have rough idle at <36°, found the problem

Hi Guys,


This last cold spell my 2003 S40 has been running really rough and stalling on cold mornings, and has had a general lack of power. The rough idle was only an issue when the temp was below 36°F, warmer than that it was just an occasional miss.


I went through replacing all of the vacuum lines around the throttle body, nothing. They needed changing, all were dry rotted, but it did not improve the cold idle. Then yesterday I went looking for more vacuum lines that might be bad... and found that the idle control valve hose was completely severed and just hanging in mid air . I have a "URO Parts 30637166 Idle Control Valve Hose" on order from Amazon. In the mean time I have it wrapped up with electrical tape and it is running much better already I cannot wait to have my turbo boost back, if I understand that hoses purpose I have been blowing all of my boost into the engine compartment.


Question:


Where the ICV hose comes out of the intercooler at the top of the radiator there are two electrical connections before and after the hose. Are these temp sensors? Airflow sensors? Is there a diverter flap that kicks in when warm in there? Just curious.
 
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Old Feb 17, 2016 | 01:14 PM
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might help to post a pic - I only get to see my S40 on the weekends when my daughter stops by the house :-( I'm guessing you are looking at the MAP sensor and a temp sensor. Not sure if the S40 has a intake preheater and actuated cold air flap like the 850s etc do...
 
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Old Feb 17, 2016 | 04:09 PM
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My notes say MAP sensor. ??
 
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Old Feb 20, 2016 | 12:36 PM
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Thanks Guys, Map and temp are correct.

Hudini, your S40 is a 2001... it looks like they added another sensor to that oval plastic bulge where the idle control hose attaches. I replaced the hose, and also cleaned my Idle control valve and made a new gasket for it. The old gasket was leaking on the inside between the two air ports Runs pretty smooth now
 
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