vacuum reading on idle

[Bean]

Hi,

for quite some time I got the feeling my engine is starting to wear a bit more than usual and although it's still driving fine and going hard I do have the feeling that something is a little off...

my engine is still completly stock and I don't see the point of changing that as long as I have the feeling something is off, as every bit of tuning would always be masked by something I haven't yet diagnosed.

So to the point

I hooked up a sensor lately to read the vacuum of my 4A-GE @idle (900rpm) and 'only' got ~40kPa (which equals ~11.8inHg)

in theory a good value should be around 30kPa or 20inHg - which is quite a bit off from my readings - though different engine get different values...

so does anyone have numbers to compare to or the option to test this aswell (easily done with a vacuum or boostgauge, as these mostly show vacuum as well)?
engine obviously warmed up and in operating temparature

Cheers Bean

PS: I do have some ideas what's wrong but would like others input first before I go there as I currently lack the tools to further analyze the problem

[allencr]

While a 4AG isn't exactly a race engine or fitted with wild cams, I'd expect it to pull less vacuum then other low stress low RPM street stuff, but still be reading similar with ever other non-diesel/rotary on the road. Reciprocating airplanes like vacuum gauges a lot, pretty much mandatory compared to just being a curiosity piece in a car.
http://www.secondchancegarage.com/public/186.cfm
Compression tests are nicer!

[jondee86]

30 kPa (abs) = 20.67" Hg
40 kPa (abs) = 17.72" Hg

Versus Toyota 16V 4AGE Service Specification of
53.5 kPa (abs) = 15.75" Hg @ 800 rpm idle.

I don't see the problem ??

Cheers... jondee86

[Bean]

Cheers jondee,

that's why I ask as I couldn't find any figures in the manual - where did you find them? (document/page)

[jondee86]

Toyota 4A-F, 4A-GE Engine Repair Manual, May 1987
Page A6 SERVICE SPECIFICATIONS at the back, bottom of the page.

Cheers... jondee86

[Bean]

doh, I certanly looked at this page at least three times but managed to overlook it - thanks alot.