performed a vacuum test need help

[MuscleInc1320]

i did a vacuum test on my car yesterday because of how its running. at idle and when driving at a steady speed, the car feels like it is lurking (like your tapping the gas pedal but the rpms dont change). anyways when i did the vac test i discovered that at idle my car is running at like 10psi with a slightly shakey needle. my book says that a low reading indicates a leaking intake manifold gas on the intake port side. which make sense to me cuz i have perfect fuel pressure and spark so i know that it cant be one of those two things. my question is have any of you had the same problem and who me having my timing bumped to 13 have an effect on the psi readings?

 

[Paul]

Bumping the timing won't affect idle. Also just FYI - vacuum is measured in In. Hg. (inches of Mercury) not psi. You should start by searching for a vacuum leak. You can spray carb/brake cleaner around various parts of the motor and if the idle jumps, it means you sprayed somewhere close to a vacuum leak. Or just look for loose/broken/unattached hoses and whatnot.

 

[MuscleInc1320]

been looking and tried the carb spray idea and still cant find it.

 

[Paul]

Your IAC or EGR can also be malfunctioning. Do you have a CEL or any codes?

 

[MuscleInc1320]

no check engine light at all so thats why i am leaning away from a sensor.

 

[MuscleInc1320]

is there a way i can test the egr valve to make sure its still good. just to eliminate that as a potential problem?

 

[Wayne]

I had a vacuum leak on my 95 Gt it was the hose that goes under the back of the upper intake plentium on the drivers side the only way I could replace the hose was to remove the upper plentium.

 

[MuscleInc1320]

when i did my hci i replaced all those hoses under the intake =/ im thinking of running air pressure through a intake vac line (with a compressor)to see if i can find the leak that way. if i did that would it hurt any of the sensors or anything?

 

[Addermk2]

is there a way i can test the egr valve to make sure its still good. just to eliminate that as a potential problem?

while the engine is running remove the vac line from the egr valve and plug said line.
Apply vaccum to the EGR valve. the car should begin to stumble horribly. if it does not, chances are good your EGR is shot

 

[MuscleInc1320]

ok i ill give that a try

 

[MuscleInc1320]

oh another thing that i forgot to mention was that the car runs just fine when i give it full throttle

 

[2002BLGT]

even with the HCI you should be pulling atleast 16 inches of vacuum at idle , definitely a vacuum leak , or your throttle blade or IAC not closing properly

 

[MuscleInc1320]

thats what im thinking but im having a hell of a time finding the problem