at idle, what should my vac. gauge read? right now it is at 9-10 in/hg at 800rpm...

 

here is the weird thing, when I hold the throttle at 2000rpm the vac. goes down to 18 in/hg or so and when I let off the throttle, it first goes down to 20-21 in/hg and then returns to 9-10 in/hg.

 

The car idles and runs fine. the only hissing noise I can hear comes from behind the p/s pump...its hard to tell what it is because the p/s pump makes noise too...

 

All vacuum lines have been replaced and the low vac has remained the same, although the car runs smoother when its cold.

 

One more thing, when I hit my 4wd, the vac surges, this is normal, right?

I am also curious about what the vac readings should be.

 

One thing I can help you with is the surge when putting it in 4WD. I assume you have a pushbutton 5 speed. There will be a little surge when activated, because the 4WD engages via a vacuum diaphragm

I am having a little difficulty with brain function as its late and I just got off work. my boost/vac gauge reads in bar. and at idle its at about -.8 bar if it is correct. so that would be a similar reading to yours. the spike on decel is normal because the motor pulls a vacume on the closed throttle plate. I will pay attention a little closer tomarow and get some real numbers.

what part are you concerned about?

ya, at idle a newly rebuilt high comp spfi reads about 21 lbs of vac, at idle, and at full throttle it goes down to about 2, and on decel it can hit as high as 25. 30 is supposedly more vac than space, and will never happen.

mine was autometer, with lbs increments.

I am concerned about the low vac at idle, and I know -.8 bar is like -11,-12 psi?(mental math) I dont know how that relates to in/hg...do you?

 

thanks for the help so far guys...

eric

I think this is it.

 

Since 14.7psi =29.92 in/Hg, then 1psi=2.035in/Hg, 12psi x 2.035=24.42in/Hg. So then your 9psi x 2.035 = 18.315in/Hg. If I am doing this correctly.

 

PSI and In/Hg are close to a 1 to 2 ratio.

 

If you suspect a vacuum leak, try checking the intake manifold gaskets. I have had trouble with those before on a couple of my Soobs. Spray some WD-40 around the joints when the engine is warm and idling and see if that makes the idle change. If it changes, then you know what you need to do.

EA82T should be around 20 IN-HG at idle....between 800-1000 rpm. At 1200 it shold do around 22.

wow 10in/hg and 20 in/hg are way different...I better investigate...

 

thanks guys

do you have cams in said vehicle?

 

only have about 10-12ins of vacuum in my XT at idle

do you have cams in said vehicle?

 

only have about 10-12ins of vacuum in my XT at idle

 

Ditto. My RX was the same.

I do have delta cams...I should have thought of that...thanks for shedding light on the matter fellas! Thats what this place is all about

So that would cause that much of a drop in vac huh?

anyway, thanks

The fact that the cams are installed. I dont know the exact science of that tho...