Hrm.. i had this problem with my escort a couple months ago.. The problem is most likely concerns the wrong air-to-fuel mixture. Now the problem with my Escort was a bit simpler. There is a link from the place where your oil is (my english sux, but i would guess that the name for that in english would be oil carter... correct me if that's not right. maybe i'll learn the word <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt='
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I would guess it's the one that right near the fan (i didnt have time to take my nissan apart yet). The pic is from an s14 but should give you an idea where to look for it... The problem on my escort was that the tube melted from the fumes and got a hole in the middle. So the cold air was suckedin through the hole directly into the engine causing the engine to shut off when i was idling (particularly at stop lights) due to excessive air. So before you buy anythin, check if there is anything suspicious there... But then again there is a difference between ford and nissan, so this thing might not be even possible to happen on the nissan. Anyways, hope this would help.