Ford Mustang Forum banner

Status
Not open for further replies.
1 - 11 of 11 Posts

·
Registered
Joined
·
24 Posts
Discussion Starter #1
okay guys i just picked up a nice 1989 Lx hatchback and it is sweet!

i have had a 1991 GT, 1996 GT convertible, and a 2000 GT.

But this one i picked up for 4500 and has a ton of new parts to come along with it.

the motor has a vacuum leak from hell.. when you pull the breather cap hose to throttle body and put your thumb over it the vacuum leak to the oil dipstick is horrid..
but idles 825 rpm..

when everything is hooked up normal its 1600rpm.. no timing jumps..

But, when you pull dipstick at 1600 rpm cause vacuum leak its not as bad at the dipstick..

it has the 93 cobra upper and lower intake and i belive the gaskets are bad.. causing the leak..

i have no idea..
the pcv valve is fine..

here is the mod list

306ci
GT40x (58cc) heads
B303 CAM
1.72 roller rockers

73 mm C&L mass air
70mm t body
Polished motorsport valve covers
Cobra INTAKE
30lb injectors
Cold air intake
All new valve train...
motorsport wiring harness that deletes EGR system
new worldclass t-5..king cobra clutch..
full subframe connectors
pypes x pipe w/cats single chamber flows with 1 3/4 headers
255lph fuel pp..fuel reg

and some other items im just to hungry to keep typing..
 

·
Registered
Joined
·
24 Posts
Discussion Starter #2
bump....bump..!

some one assist me please!
 

·
Registered
Joined
·
13,166 Posts
spray tb cleaner around the intake it will tell you where the leak is.
 

·
Registered
Joined
·
24 Posts
Discussion Starter #4
I know that.. I haven't gotten to try I yet..

but what else would cause a leak that bad??
 

·
Registered
Joined
·
23 Posts
If you have a properly functioning PCV system, then what you describe is normal.

At idle the intake is pulling vacuum, this vacuum pulls through the open PCV valve. When it does this the air has to come into the crankcase from somewhere. In this case it is entering the crankcase through the tube between the throttle body and the oil filler neck. This is why the tube is positioned upstream of the throttle blade.

When you plug this tube with your thumb, the air entering the crankcase has to come from somewhere else. In this case it will try to draw the air through the oil dipstick tube.

When the motor is under load, and blow-by is produced, the same tube between the throttle body and the oil filler neck allows crankcase pressure to flow the other way, from the filler neck to the throttle body.

Do a search on the PCV system, there have been some good diagrams with explananations posted in the past.
 

·
Registered
Joined
·
24 Posts
Discussion Starter #6
If you have a properly functioning PCV system, then what you describe is normal.

At idle the intake is pulling vacuum, this vacuum pulls through the open PCV valve. When it does this the air has to come into the crankcase from somewhere. In this case it is entering the crankcase through the tube between the throttle body and the oil filler neck. This is why the tube is positioned upstream of the throttle blade.

When you plug this tube with your thumb, the air entering the crankcase has to come from somewhere else. In this case it will try to draw the air through the oil dipstick tube.

When the motor is under load, and blow-by is produced, the same tube between the throttle body and the oil filler neck allows crankcase pressure to flow the other way, from the filler neck to the throttle body.

Do a search on the PCV system, there have been some good diagrams with explananations posted in the past.
thanks! but... my idles stuck at 1600 rpm unless I have my thumb over that one tube from breather to throttle body.. I want it to idle normal...
 

·
Registered
Joined
·
604 Posts
A bad idle could have nothing to do with vaccume, could be your TPS or MAF or any number of things, did you clean your TB or MAF sensor recently? Using the wrong cleaner can cause that or junk in the IAC.
 

·
Registered
Joined
·
604 Posts
The reason your idle goes down is you are choking the air supply.
 

·
Registered
Joined
·
24 Posts
Discussion Starter #9
A bad idle could have nothing to do with vaccume, could be your TPS or MAF or any number of things, did you clean your TB or MAF sensor recently? Using the wrong cleaner can cause that or junk in the IAC.
no its all BRAND NEW.. everything the motor from intake to oil pan is brand new.

just a idle thats 1600 rpm... with the crazyest amount of vacuum coming from the oil dipstick when i pull it...

than when i plug that one tube... the idle drops to 825... but then that much more vacuum is coming from dipstick when you pull it..

soo im so lost... its unreal...

is it a bad thing.. i have no clue how to set the idle down and just live with the vaccum or take the intake off and put differnt gaskets and try to fix it..


the guy i purchased it from said... he used fel pro BIG BORE gaskets??

i belive thats why its pulling vaccum??

so i went to auto zone and go 93 cobra upper/lower.. and lower to head gaskets.

so im going to try that...if that dont fix it.. who knows what will..


and with my set up what do you belive the car should run 1/4 mile?
 

·
Registered
Joined
·
2,003 Posts
the gaskets sholluld fix your leak - bet it's leaking on the lifter valley into the intake.....
 

·
Registered
Joined
·
24 Posts
Discussion Starter #11
the gaskets sholluld fix your leak - bet it's leaking on the lifter valley into the intake.....
I sure hope sooo!!
 
1 - 11 of 11 Posts
Status
Not open for further replies.
Top