www.automedicsafrica.com


Have you ever tried to tune an engine only to find it won’t idle or run right? Or have you ever been confronted with an engine that just doesn’t seem to run right no matter what you’ve done or replaced? You may be dealing with an engine vacuum leak.

Sometimes an engine vacuum leak will whistle or hiss and make itself obvious. But oftentimes, a vacuum leak will disguise itself as an ignition or fuel problem that defies diagnosis. Either way, an engine vacuum leak is bad news because allows “unmetered” air to enter the engine and upset the air/fuel ratio.

So how do you know when an engine vacuum leak is causing a problem? If the engine is experiencing any of the following symptoms, a vacuum leak is probably responsible:

*Too fast an idle speed: If an engine without computerized idle speed control is idling too fast and refuses to come down to a normal idle speed despite your best efforts to back off the carburetor idle speed screw or air bypass adjustment screw (fuel injection), air is getting past the throttle somewhere. Common leak paths include the carburetor and throttle body gaskets, carburetor insulator spacers, intake manifold gaskets, and of course, any of the engine’s vacuum fittings, hoses and accessories. It is even possible that leaky O-rings around the fuel injectors are allowing air to leak past the seals. Another overlooked item can be a worn throttle shaft.
*A rough idle or stalling: A performance cam with lots of valve overlap can give an engine a lopping idle, but so can a vacuum leak. A really serious leak can lean the air/fuel mixture out to such an extent that an engine won’t idle at all. An EGR (Exhaust gas recirculation) valve that is stuck open at idle can have the same effect as a vacuum leak. So too can the wrong PCV(an automotive-emission control valve that recirculates gases (as from blow-by) through the combustion chambers to permit more complete combustion) valve (one that flows too much air for the application), or a loose PCV hose. The rough idle in these cases is caused by “lean misfire.” The fuel mixture is too lean to ignite reliably so it often misfires and fails to ignite at all. Lean misfire will show up as elevated hydrocarbon (HC) readings in the exhaust, enough, in fact, to cause a vehicle to fail an emissions test.
*Hesitation or misfiring when accelerating: This may be due to a vacuum leak, but it can also be caused by a weak or inoperative accelerator pump in a carburetor, dirty injectors, or even ignition problems such as a cracked coil, worn spark plugs or incorrectly gap plugs.
*An idle mixture that defies adjustment: When setting the idle mixture adjustment screws on a carburetor, the idle speed should start to falter as the adjustment screws are turned in to lean out the mixture. If the screws seem to have little or no effect on idle, you have either got a carburetor problem or a vacuum leak.

for more go to; www.automedicsafrica.com

Also good to note that diesel engines do not produce vacuum.

CityNG: Also good to note that diesel engines do not produce vacuum.

I bow my automotive head in shame, never new this

GAZZUZZ:

I bow my automotive head in shame, never new this

Where all learning together.

All these time I though VW VR6 engines were in a V shape. Never knew that they were siamesed.

CityNG:

Where all learning together.

All these time I though VW VR6 engines were in a V shape. Never knew that they were siamesed.