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vacuum leak test

L

L78MARK

New member
I am having a problem with a high idle with my 2000 GTP, I checked the IAC and that is OK so I think
I may have a vacuum leak somewhere. the vacuum lines are all good and have no leaks. What should
the vacuum reading be at idle after the engine is warmed up and where should I get the reading from.
Should I get it from the front of intake or at the T on the top of the supercharger.
Thanks
Mark
 


spray some carb cleaner at the vac lines, if the idle jumps you found your leak area. move the lines around if you find nothing the first time round.
 
I hate carb cleaner, it just bogs the motor. Thats why it'll never start with that crap if you spray it in the intake. Use brake cleaner instead.

But you'd have to have some huge vacuum leak to notice an rpm jump, easier to just watch fuel trims. If they change when sprayed, you've found the leak.

Normal intake manifold pressure/vacuum is normally around -19 to -20in/hgs. And fuel trims on the LONG TERM within 5% of zero, if they read +16.4 you have a vacuum leak somewhere.
 
carb cleaner made my idle fly up when it hit the busted vac line i had. only the lines crack was closed with its weight on in, so lifting the lines and spraying made it show its face.

starting fluid will also work if you got that on hand.
 
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