Rough idle, low vaccum HELP!!!!

[CSXTacy]

ok so i went out to start my redtop Sr today to let it run for a while. i cannot drive it yet since i have yet to purchase wheels so i have been letting in idle in the garage. yet today when i started it and let it idle it had a high idle 1200rpm so with the iacv screw i turned the idle down to about 900 rpm. when i went to give the vehicle a little juice i reved it to about 3500rpm and let it fall back down to idle but it dropped down to a substantially low rpm something like 550 rpm and almost died. it barly recovered on its own, what could cause this??? it happens every time i rev the engine on decel it drops to a very low rpm and sometimes even dies. also it should be noted that the fuel pressure is 40psi at idle, i only have 8 in hg of vaccum as well a buddy told me that is super low, what could be the cause of such low idle vaccum???? thanks to all!!!!

[nism014]

I think if you have a blow off valve that blows into the atmosphere then thats normal. My idle drops down that low also when I rev it up high and let off. Well thats what I've been told.

Some one needs to confirm this...

[Z U L8R]

put the idle adj screw back where it was. it's normal for a car to idle high cold.

[misfitsfreak81]

you have a serious vacume leak by the sound of it. 8in/hg is way low. check all your vacume lines as well as all intercooler plumbing conections. yes a high idle is normal on a cold motor though it should drop down pretty fast and smooth out.

mike

[CSXTacy]

awesome i will definatally check those things also another guy told me that if the timing is off that could cause low vaccum anyone have any other suggestions or input?? thanks to those that have already posted!!

[slider2828]

Use a spray bottle with a lot of dish washer soap and a little bit of water. Like 1/4 of water and 3/4 dishwasher soap. Spray on all couplings and all vacuum lines. Keep your eyes open, bubbles mean leak. Good Luck

[Birdman12]

where is the idle adjuster screw located??

[CSXTacy]

it's located on the Idle Air Control Valve which is attatched to the intake i believe the screw sits between the 3-4th intake runners I could be wrong as i am not looking at the car now but you can definatally see it

[SSC299]

Make sure you're checking the idle after the car is warmed all the way up. As stated before, the idle will be high on a cold motor. I had the same problem and I just needed to adjust the aicv. It was bucking (just like a vacuum leak) between cruising and boosting.