98 EX M/T


First off I did a search and found one about this same thing but no answers. And no it is not the intake, I have had the intake on it for 6 months, this just started yesterday. And I have checked the intaked for leaks. That said onto the problem.


Just had my car apart to install some amps and an EQ. It was down for about two weeks(not driven or cranked). Now when I am driving the idle dips down everytime i let off the gas. And there is a hissing sound(like air being sucked or blown through a straw) coming from the engine bay, the sound continues for a second or two after the car is shut off. Then it just dies down to nothing. It ran great before, none of these problems where there. What is wrong do you think?

 

Definitely sounds like a vacuum leak. Get a can of carb cleaner (with the little red straw) and spray around the engine bay with the motor running. When you spray in the area of the vacuum leak, the engine will stumble or surge.

 

Is there some way other than spraying flamable liquids on a hot engine? I have a vacuum pump, can it be used?

 

dont worry about carb cleaner it will vaporize once it hit the hot surface, all you have to do it spray it around all the vaccum hose,throttle body and all part of intake tube manifold. the idle should rise the carb cleaner suck and then u found the leak.
vaccum pump cannot be use to ck for vaccum leak, vaccum pump applies vaccum.

 

i made a few posts where i just recommend replacing all the vacuum hoses.
i had the case a couple of years ago where i needed to (rough idle and idle speed racing up and down).
did them all except for the large one off of the brake booster.

you can look at the hoses but cannot tell if they are bad. cost is between 2 or 3 dollars. but my car is an 88, and i think all the hoses were original. your's is much newer - so i don't know.

 

Yep, vacuum leak. Spray carb cleaner around as suggested. Don't worry, it won't start a fire.

If you find a leak around the manifold, you will need to replace the gasket and make sure to torque all the bolts down the spec... if you still have a leak you may need to check the flatness of the mating surfaces and take them to a machine shop if they're bad (it would probably be the manifold, not the head).

But check the vacuum lines before you tear anything apart... I'd hate to see you take it all apart when a simpler problem was to blame.