this post islong but please help me i can't figure it out

[thornton22050]

Hey guys thanx in advance for the help. My cars vacuum is low about 10in and i cannot figure it out. i did a boost leak test didnt find anything, i did a compression check all cylinders came back bettween 180-190 so to me this means all internals are fine and my timing isnt off. my idle wasn't real bad and then today everything got crazy. i turn her on she idles up about 1200 rpms to warm up, after she warms up she idles like sh*t about 300-500rpms but never tries to die just idles low and boost gauge is going crazy bettwen 5- 1inhg. get on the highway for 15 mins get off car vacuum is back to 10 inhg and idle is relitavely normal again. get off work same thing happens exactly. im stumped completely cant figure this out. the only problems with the car is a exhaust leak where the cat meets the downpipe

 

[silver bullit]

You need a new idle controller, vac is at normal. when you are at idle or not boosting the motor is drawing in air which is vac on a boost gauge.

 

[thornton22050]

i know pulling vac is normal. what im saying is my vacuum should be pulling harder between 18-20 correct? and if i do need a new idle controller why dosent it idle like sh*t all the time? and even if it is the idle controller that dosen't explain why my vac pressure is so low

 

[silver bullit]

i know pulling vac is normal. what im saying is my vacuum should be pulling harder between 18-20 correct? and if i do need a new idle controller why dosent it idle like sh*t all the time? and even if it is the idle controller that dosen't explain why my vac pressure is so low

10-20 is normal, your ics is bad, it needs to be replaced. It fluctuates because the ics is not working correctly.

 

[thornton22050]

ok im not trying to be a jerk but im pretty sure a pulsing vacuum pressure between 11-8 inhg isnt normal when i say pulsing i mean needle jumping extremely fast. none of my other dsms ever vaced this low and my sti def dosent vac this low.

 

[Elvenhome21]

my car is aroumd 10 also, I checked everything over twice and came up with nothing. I am not to worried about it because gas mileage isn't anything to complain about. You could turn up the BISS to get it to idle a little faster.

 

[thornton22050]

anymore opinions cause im still not conveinced its my isc

 

[BISHILVR]

Isc would'nt cause that. Low vacuum is not related to a bad isc when letting off the throttle on the highway. I would say that you have a blown intake mani gasket, or cam timing that is off a tooth, etc. Something mechanical wrong would be what I would be looking for.

 

[timloomis]

Yea like he said,your cams might be a hair off.Mine were at one point.The idle went nuts,low vaccuum,etc...The exhaust cam was off 2-3 teeth,now it runs fine and has 18-20 inhg at hot idle.

 

[thornton22050]

i compression tested the motor everything comes back perfect180-190 across the board so dosent that rule out timing jump? im gonna boost eak test again and ill let you guys know

 

[slipstream808]

Check to make sure those cams are lined up correctly. Trust us on this one.