Vacuum drop after PI Swap

[SFC.Kill]

My gauge was reading 12hg at idle before Full PI Swap. Now it is reading 6hg is that because of the increased compression ratio? I noticed to after swap my car idles at 1000, was at 700 before swap do I got a problem somewhere. Pulled off IAC connector and no change in idle. I drilled and tapped the PI intake so I have both coolant sensors. Also my idle hangs too. Might have to do IAC mod.

 

[the98stang]

It's pulling in air somewhere from a vacuum leak. Use a butane torch to find the leak (butane will cause a rise in RPM once the leak it found). Check all vacuum hoses, especially the ones you removed for the swap.

 

[bhuff30]

Yup, definately a vacuum leak somewhere. Even 12" Hg seems a bit low. Another trick is to use starter fluid and spray in various places you suspect. If the idle speed increases, you found the leak.

 

[SFC.Kill]

Cool, will check it out.

 

[Red04GT]

It's pulling in air somewhere from a vacuum leak. Use a butane torch to find the leak (butane will cause a rise in RPM once the leak it found). Check all vacuum hoses, especially the ones you removed for the swap.

i do not suggest using a TORCH to check for vacuum leaks. Plastic intake......propane is an option but the safest way is to check the car is with a smoke machine. but i know most people dont have access to one.

 

[jivepepper]

There's a vacuum leak some where.

 

[SFC.Kill]

You don't light the touch, just turn the propane on. Wherever the vacuum leak is it will suck in the propane increasing the idle. I hope you were only kidding.

 

[squeak93]

+1 on the major vac leak. Souds like with your coolant leak and vac leak, your for sure going to be pulling the lower intake.

 

[justinschmidt1]

Im pretty sure my car is usually pulling about 20 hg vacuum at idle

 

[Skud]

I pull 15" and that's with MPH blower cams..

I think 20+ is normal for stock cammed cars.

Riley

 

[smasher41]

yeah, im about 20 also with full PI swap... somthing is wrong, very wrong.

 

[Winters98GT]

Yup, definately a vacuum leak somewhere. Even 12" Hg seems a bit low. Another trick is to use starter fluid and spray in various places you suspect. If the idle speed increases, you found the leak.

I agree, but always be careful. I've used it to find a leak on a fuel injector, but stood back knowing it's flammable.

 

[SFC.Kill]

I found 3 leaks, a intake manifold bolt was even tighten, back in the right corner there is about a 3/8 inch rubber vacuum hose that goes from the back of the plenum, to some sort of black round valve, that hose is falling apart in my hands. Found coolant leak at back of thermostat housing.

 

[squeak93]

Did ur vac get any better?

 

[Red04GT]

You don't light the touch, just turn the propane on. Wherever the vacuum leak is it will suck in the propane increasing the idle. I hope you were only kidding.

yes i was kidding. but it does sound funny when someone says torch and vacuum leaks. i just like using a smoke machine.

 

[SFC.Kill]

Yeah it was the vacuum line going thru the firewall up to my gauge, the rubber grommet came loose so the plastic line had the leak.