OK say you want to check your engine for vacuum leaks (unmetered/false air) with a vacuum gauge (as far as I know a vacuum gauge would be the easiest way). Now, even a slight vacuum leak should show lower vacuum reading right? And might make the idle a little rougher, and the idle speed slightly higher, maybe not noticably higher, but the higher idle is where my my question lies. On a fuel injected car with IAC wouldn't the computer readjust the idle within it the IAC's limits to normal rpm by closing in the IAC and therefore the vacuum and idle speed would seem normal, yet there would still be unmetered air getting into the intake (the main problem with a vacuum leak in the first place)?
I think if you hook up a scanner or go into diagnostic mode you get a constant IAC, so I assume then if you don't have approx 20 in a vacuum, there might be a leak, but what if you don't have it in diagnostic mode? Can anyone shed some light on using a vacuum gauge to check for vacuum leaks?
I think if you hook up a scanner or go into diagnostic mode you get a constant IAC, so I assume then if you don't have approx 20 in a vacuum, there might be a leak, but what if you don't have it in diagnostic mode? Can anyone shed some light on using a vacuum gauge to check for vacuum leaks?
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