Toyota MR2 Message Board - View Single Post

mr2greasemonkey · 05-31-2007, 09:32 PM

This is where a decent vacuum gauge comes in handy. Even a cheap one from a retail parts store will get you by. Vacuum (manifold pressure) is a very good indication of how well the cylinders are drawing in air and sealing the chamber off. You should have a nice smooth reading on the gauge at idle ( assuming you dont have a lumpy cam) that changes quickly when the throttle is bliped and recovers quickly. If you've ever had a misfiring engine and had the chance to use a vacuum gauge on it you can see the change in manifold pressure as a bouncing needle. Anything that leaks air in the intake will show low engine vacuum. You generally want to see 18-24 in. vacuum on an NA engine. If you have enough vacuum hose you can take the car for a spin with the gauge hooked up to see how well the engine is "pumping".

Intake leaks are a whisteling sound that goes away when the engine is revved. A 2 foot long piece of heater hose and your ear is almost as good as any electronic listening device. Just put one end to your ear and move the hose around to gaskets/seals on the intake that you suspect may be leaking. If you like to party, a party fogger is a cheap alternative to a nitrogen leak detection system. All you need is a bunch of vacuum tees in different sizes and a good place to tap into the system. Let the machine warm up, push the button and look for whisps of smoke.

05-31-2007, 09:32 PM	#13 (permalink)
mr2greasemonkey Once again....yups Join Date: Sep 2005 Location: Portland, OR Posts: 1,658 Thanks: 4 Thanked 63 Times in 42 Posts iTrader Rating: (0/0% )	Vacuum leaks, low manifold pressure This is where a decent vacuum gauge comes in handy. Even a cheap one from a retail parts store will get you by. Vacuum (manifold pressure) is a very good indication of how well the cylinders are drawing in air and sealing the chamber off. You should have a nice smooth reading on the gauge at idle ( assuming you dont have a lumpy cam) that changes quickly when the throttle is bliped and recovers quickly. If you've ever had a misfiring engine and had the chance to use a vacuum gauge on it you can see the change in manifold pressure as a bouncing needle. Anything that leaks air in the intake will show low engine vacuum. You generally want to see 18-24 in. vacuum on an NA engine. If you have enough vacuum hose you can take the car for a spin with the gauge hooked up to see how well the engine is "pumping". Intake leaks are a whisteling sound that goes away when the engine is revved. A 2 foot long piece of heater hose and your ear is almost as good as any electronic listening device. Just put one end to your ear and move the hose around to gaskets/seals on the intake that you suspect may be leaking. If you like to party, a party fogger is a cheap alternative to a nitrogen leak detection system. All you need is a bunch of vacuum tees in different sizes and a good place to tap into the system. Let the machine warm up, push the button and look for whisps of smoke.