# Intake manifold leak



## ddorgan (Feb 1, 2012)

Have a 1993 pickup that has had a rough idle for a couple of months. I have changed plugs, rotor, cleaned egr valve, cleaned throttlebody, cleaned fuel injectors, tested sensors and no codes on ECU. Just by chance, I sprayed carb cleaner around the intake manifold and the idle seemed to increase and smooth out. I am thinking that the intake gasket is bad. Before I go to the trouble of changing the intake gasket are there any other tests that I could do to make sure that the gasket is bad


----------



## TheRepairMan (Jun 30, 2009)

It sounds like you have it covered pretty well already. The carb cleaner test works fairly well. I've also used WD40. You just have to be careful not to create a flash fire with any spray you use.

I also usually try to confirm a intake leak with the open ended hose on my mechanics stethoscope. You would be surprised just how easy it is to hear a vacuum leak this way. If you don't have a stethoscope any old extra piece of small diameter hose will work. Put one end up to your ear and run the other around the intake manifold gasket flange. You'll notice a big change in the rush of air when you find it.

And, BTW, Harbor Freight usually has mechanic stethoscopes for about $4.00 or so.

-Roger


----------



## jdg (Aug 27, 2009)

TheRepairMan said:


> Put one end up to your ear


UP TO your ear, not IN your ear.
I can just see the next post being something about needing to go to the doc for a blown eardrum.


----------



## TheRepairMan (Jun 30, 2009)

jdg said:


> UP TO your ear, not IN your ear.
> I can just see the next post being something about needing to go to the doc for a blown eardrum.


Yeah, that's WHAT I SAID! Gosh! Do we have to warn people about every little thing? LOL! Now days the way everybody is so sue happy I guess you can't be too careful.

Do NOT touch the stove top while hot... It may cause severe burns!

Do NOT eat ice cream too fast... your brain will freeze! 

Do NOT point the pressurized air nozzle towards someone's anus and pull the lever! ...Don't ask me how I know that! 

I mean, some things should just be common sense... but some people have none... I do realize that.

Case in point... I pulled up to the gas pumps one cold Winter day and the guy in front of me was in an old classic car having difficulty getting the key to go in and turn the locking gas cap. After trying a short while he got out his cigarette lighter, clicked it, and proceeded to try to heat up the lock on the cap!!! Uh! I slammed my car into reverse and floored it backward wide open! In point 05 seconds I was out of there. I didn't stick around to see the results. Are people really THAT stupid?


I understand there is some liability to every action we take, but people have to assume some personal responsibility for their own actions, too.

And, actually, when I use the open hose on my stethoscope I'm taking some chance that negative pressure could damage my ears, but you have to make sure you don't stick the end of the hose directly flat up against anything that might seal it off to engine vacuum. When looking for a leaky intake gasket around the manifold flange and head that would be almost impossible to do. In my 40 years of doing this it's never happened to me.

That said, one has to be very careful doing any kind of testing around a running engine. Wouldn't everyone agree? I know some guys that still spray gasoline around the engine to check for vacuum leaks. No way I'm going to condone that! Besides don't they know that's only real effective for checking for ignition problems??? LOL! DO NOT TRY THAT AT HOME!

-Roger


----------

