How do I know if there is a crack in the intake manifold?

You were probably just farting out some WD40 mist. You'll know if there's a crack in the intake manifold.

ONCE CRANKED UP---SPRAY A LITTLE STARTER FLUID IN THE AREA YOU SUSPECT A CRACK---IF THE ENGINE REVS UP A BIT--YOU MAY HAVE A CRACK

ANOTHER THING YOU CAN DO IS TURN ON A PROPANE TORCH (PLUMBER TYPE) ****DO NOT LIGHT IT!**** JUST WAVE THE GAS OVER THE SUSPECTED AREA--IF CRACKED, IT TOO WILL MAKE IT REV A BIT

JUST DO NOT SPRAY IT IN OR CLOSE TO THE THROTTLE BODY---IF IT S. UCKS SOME DOWN THE THROAT---IT'LL DO THE SAME THING!

MY GIRL HELPED ME RESTORE ONE OF MY JEEPS! SHE HELPED FOR 2 YEARS. HER BIRTHDAY IS MY HOOD NUMBERS

THIS IS HER IN '91 WHEN WE GOT "WILLY" DRIVABLE, ABOUT 4 YRS OLD

THIS IS HER IN '97, AGE 10, PROFICIENT IN DRIVING "WILLY", 4X4, HANDCRANKING, BASIC MAINTENANCE

THIS IS HER AND MY GRANDSON IN 2010, VISITING. NOW 23 YRS OLD

THE MEDIC

Just be very careful doing that method. I do it all the time, and I showed a guy who I was training how to do it. He tried to do it to diagnose a leak and got the plug wire wet, which little did he know was arching against the head, and the top of the motor went up in flames. Luckily the starting fluid burned off in a matter of seconds, but it could have gotten very ugly.