neg19psi at idle pos4psi at WOT

[89DodgeSpirit]

noticed something weird tonight

at idle on cold engine I get 19 inches of vacuum

once it heats up (been driving it around)

I only get like 15 inches of vacuum... Is this "normal"?

I was also thinking that maybe my intake manifold gasket or however it seals is bad... Think that may be it? It sounds like a sucking noise coming from behind/around the intake manifold at idle that I just cannot pinpoint.

At WOT I get like 3 or 4 psi but anything under WOT it is like 10 or 15 vacuum... If I change RPM at idle from like 750 to 2500 the vacuum decreases for a short while and goes back up.

I compeltely blocked off the stock BOV lines tonight (the ones I could find) and I can hear the turbo spin up and run more than I could before but I think that I still have some sort of major boost leak (seeing as how that I still only get 3 or 4 psi boost at WOT and anything under it no boost =)

Suggestions accepted

Sorry if I have repeated anything - bad habit!

Thanks! =)

Quote:

Originally posted by 89DodgeSpirit once it heats up (been driving it around) I only get like 15 inches of vacuum... Is this "normal"?

I always have 19 inches (vacuum) at idle... hot or cold. I don't know if this would work (considering where the intake manifold gasket is), but You can try... With the engine running spray short bursts of WD-40 at the gasket area. If you get a fluctuation in RPM you get bet there is a leak. Just be VERY carefull! If you're under the car it's a good idea to have someone else around.

I would think, though, if you have a leak your guage would be kind'a jumpy at idle.

[89DodgeSpirit]

I really don't know... I am going to install my intercooler & piping for it here in about 4 or so days... and I will replace as much of the vacuum lines as I can - and I will see how the gauge stands... Then I will go from there.

If I need to go so far as to get a new gasket and install it or so far as to get a new turbo I will do it... It's worth it if you ask me!

From what I understand spraying water at the gasket area will calm the engine - safer than spraying something highly flammable at a hot engine =)

[GovtContact]

Well, the way I see it is if you are going to be doing a IC and a new BOV and you are going up against a '98 (????), check your compression. If uneven presure, pull the head, replace the gasket, Have the turbo upgraded and ported (Mike at Majestic Turbo in Dallas did a great job on mine and was a good price, see some one of my other posts for info and link). Lay your IC tubing, slap on a new Head gasket/head bolts, vac lines ect.

As far as helping with the vac lines. Find one end. find that end on the diagram. As your hand moves down the line, move your finger down the diagram. When the end of either the diagram or line is reached, stop and check that the two are the same. If they are not the same, make them the same.

[89DodgeSpirit]

head's been restored fully and I have a mopar high performance headgasket with 500 miles on it.

And it is a 98 Grand Prix GT 3800 - AKA 200hp 220ft-lbs Torque

I am going to be upping my boost before this race to 14psi with grainger boost controller & having my intercooler & BOV installed. Hopefully if I don't slip & slide I should win =)

found out why I am only getting 15" of vacuum at idle when I was getting 20"

bad vacuum check valve.

I was just wanting to test the vacuum first hand (I am just like that) so I found the easiest vac line to unplug which was the small one from the TB to etc... well I unplugged it after my T to my boost gauge right before the check valve - plugged it with my thumb and it went right to 20"... plugged it back onto the valve and right back to 15" =) VERY lucky =) I could have gone years and never found this vac/boost leak =) To the dealership for a new vac check valve it is!!! LMAO!

And while I am there I will pay for my door clips & pick up an orifice. Then I will see what happens then *crosses fingers*

[sethyboy2003]

still having boost issues? no time to read all the posts but my bro's mini would only get 3-4psi on WOT and the wastegate actuator was not hooked up to the swingvalve. hooked it up wahla 11psi

[89DodgeSpirit]

swingvalve? Where is it located and what does it do?

"swingvalve? Where is it located and what does it do?"

It's the wastegate..... the part that dumps the 'waste'! It's in the elbow off the turbo. All you can see (or feel) of it is the shaft and arm. Your actuator is connected to it by the rod.

[89DodgeSpirit]

replaced the faulty check valve today
unplugged wastegate can
9psi at near WOT

Hey it's better than constant vacuum or near 0 (1-2) =)

I bet I have dryrotted hoses leaking - I know the one that goes to the stock BOV is dryrotted pretty bad. Now I just gotta grainger & install my intercooler =)

That wicked wicked mitsubishi turbo noise! I love it!

[firebaron90]

i have two questions about that diagram...... the waste gate solenoid.... the middle barb is the inlet, the bottom is a filter, what is the top???? there is nothing there in the diagram, yet the rubber piece that has the filter and original hard lines that pluged in, there is a line to the upper barb. Any ideas to where this goes???

Also, what is the purpose of the check valves and the orifaces??? are they needed??? what lines MUsT have them???


Joe

[89DodgeSpirit]

Quote:

Originally posted by firebaron90 Also, what is the purpose of the check valves and the orifaces??? are they needed??? what lines MUsT have them???

The check valves keep the boost pressure from pressurizing the vacuum lines while under boost. Basically it keeps the boost only in certain parts of the vacuum circuits while under boost... But they let all vacuum lines see the vacuum when there is any. Basically you can't blow air out of the intake manifold thru the small vacuum line but you can suck it into the manifold via that line.