Is it possible for me to test for a vacuum leak, if so how do I do it. The reason I ask is because my RPM guage jumps up and then down almost all the way when I start my car. I was told it could be a vacuum leak but don't know how to check for it.

 

if it only does it once, it's normal. If it REVs......like up and down, up and down....then it's very likely a vacuum leak. Get out your helms manual (if you don't have one, go get a haynes at least down at the local auto parts store for all of $12 - best investment you'll make for $12).....and go through the tests that it describes.

It may also be your IAC valve, which there is a test for that in the Haynes/Helms as well. if that's the case, get a new one from a junk yard intake manifold. Also check for any unplugged vacuum hoses (I know it's obvious, but if you've been doing work under the hood, you may have forgotten one or something).

- Nathan

 

even if it's not a vacuum leak it would be a good idea to make a tester anyways to test for cracked vacuum lines or what not.. easiest way is to use a bike pump.

get a cap to fit your intake..
get a fitting for the cap and tap it in..
buy a hose to connect to the bike pump.
plug up the line that goes from the intake to the valve cover

then pump away.

 

Thanks for the help. I noticed a hose thats not connected on the top of the big hose that connects from the Radiator to the back of the engine where the thermostat is. The hose is being held in place but the end is just open. There is nothing connecting to it. Could someone tell me what this hose might be for. Its right on top of the hose that connects to the thermostat. I have looked in the book and can't find it anywhere. Is is connected somewhere on one end but the other end is just open. By the way I have a 1998 Accord Coupe 4Cyl. if that helps.