ZachW04Stang

I did a vacuum test today. It was staying steady jump between 18 and 20 at idle but every minute or so the engine would sound like its bogging down, idle would drop and vacuum would go to 15. I sprayed down around all parts of the intake manifold gaskets with soapy water as well as the vacuum lines that I could access but only found one slight problem. Right behind the throttle body I found a indent in the intake manifold that bubbled very slowly but it looks like the indent was there from the factory. I haven't done a tune up yet so I'm going to get on it this weekend, but I would think that normal vacuum on a v8 would be staying 20 or 21. I also hear a clicking on the right side of the engine. I think theres a leak where the manifold meets the head. When I turn the car off you can still hear a metallic clicking sound coming from there.

wildstang87

the clicking noise when you turn the car off is most likely the manifold/header cooling off, as for vacuum yours is right on, 5.0s normally run between 18-20 in of mercury at idle. the bog might be an electrical load such as the voltage regulator kicking in putting the load on the alt. how does the idle act??? also soapy water isnt used for finding a vacuum leak, especially at the intake, use carb cleaner, or starting fluid, that way it will pick the idle up if you suck some up, which will indicate a vacuum leak. this method works the best. also spray behind the passenger strut tower by all the solenoids, they tend to leak alot. i hope you find whatever problem youre looking for.

ZachW04Stang

The cars idle is pretty steady, it jumps from 700-800 but idle will drop to 500 then shoot up to 1100 and the engine will shake then even out again. I don't see this being normal.

wildstang87

actually the rolling idle is pretty normal on the 5.0s. it is cureable but normal for alot of us. see the sticky above for steps to try to cure this.

99saleen351r

Ya you defiantly dont want to use soapy water...LOL you should use Wd 40 or starter fluid or carb cleaner..Chances are its fine anyways.What made you start looking at this anyways??

stanglx2002

This should help your problem with the rolling idle clean the IAC with carb cleaner and then replace the pcv valve ans screen.