rough idle at stop lights

[darkstar1313]

I drive 40 miles to work each day. On the way to work 3/4 of my trip I am on the highway. When I get off the highway and come to the first stoplight my idle will fall from the normal 800 down to 500. It will kind of stumble there for a minute and then go back to normal. For the rest of the way to work at most of the stop lights it does the same thing. when I get to work and park it is perfectly fine. Now on the way home it never happens. The idle is always perfect. The only differences between going to work and home, is on the way home I coast down a moutain before i get off the highway and I am not on the throttle for the last 5 miles of my drive. The difference in altitude between home and work is about 2500 feet. I have changed the idle control sensor, the trottle positioning sensor and the fuel filter within the last year. I don't see any boost or vacum leaks. I have searched the forums for my answer, but have not found my answer. Could the altitude be changing something, maybe the fuel pump. Also my logger has shown no error codes.

Thanks for your help.

 

[BoostFrenzy]

Is your BOV vented? Do a Boost leak test just in case. The elevation change might have some sort of effect on idle because idle uses vacuum and you are not pressurizing the system with a turbo. If your BOV is vented that would be a problem when you let off the gas. (but i don't think i need to go through that now do i? )

 

[darkstar1313]

The BOV is not vented to the atmosphere.