I'm coming back to report the result. I fixed the problem which was caused
by EGR valve failure. I tried to clean it but after a while, it failed
again so at last I bought a new one and then everything was perfect.
Thank everyone here. I got many useful advices.
Good luck.
--
Message posted using
http://www.talkaboutautos.com/group/...makers.saturn/
More information at
http://www.talkaboutautos.com/faq.html