Low vac and only 5 boost

imrtllioness

Registered User
Ok I have a 94 sc has a 10 % pulley on it.. it has had 12 - 15 boost until recently .. it wont go over 5 boost.. the super charger sounds fine.. No found leaks in system... also it only has maybe 5 psi vac at idle.. I checked the bypass valve and it seems to operate properly .. Oil in the supercharger is good.. I did however find that the bolt was missing from the tps.. would this have been causing the problem .. even though it did NOT set any codes..? if not I am not sure where else to look
 
Ok I have a 94 sc has a 10 % pulley on it.. it has had 12 - 15 boost until recently .. it wont go over 5 boost.. the super charger sounds fine.. No found leaks in system... also it only has maybe 5 psi vac at idle.. I checked the bypass valve and it seems to operate properly .. Oil in the supercharger is good.. I did however find that the bolt was missing from the tps.. would this have been causing the problem .. even though it did NOT set any codes..? if not I am not sure where else to look

If the car feels like it runs about the same, it's probably just a leak in the small hose that attaches to the boost/vacuum gauge.

David
 
First thing I would do is cut the zip ties!! They can crush the hose/tube giving you a low reading. :eek: Also, check to be sure the hose to the gage is not crimped, as this will do the same thing.
 
and where is this hose located.. I have zip tied all vac lines so I dont know where to go from here

It attaches to the return plenum (part that lower IC tube attaches to) just behind the air temp sensor. The hose runs through the firewall and attaches to the back of the boost/vacuum gauge. It's a hard nylon tube about 1/8" ID and has rubber connectors on each end. Most common place for leak to happen is at the rubber end connection on the return plenum. This can usually be repaired with a short section of vacuum hose and some zip ties.

David
 
First thing I would do is cut the zip ties!! They can crush the hose/tube giving you a low reading. :eek: Also, check to be sure the hose to the gage is not crimped, as this will do the same thing.

The zip ties are only used on top off the vacuum ports themselves. You aren't going to crush the vacuum lines in those spots. Most of the members here use zip ties on the vacuum port locations for years with no trouble at all.
 
The zip ties are only used on top off the vacuum ports themselves. You aren't going to crush the vacuum lines in those spots. Most of the members here use zip ties on the vacuum port locations for years with no trouble at all.

True...every and I mean every, push on rubber hose connection on my car has a zip tie securing it.

David
 
Sadly it is pouring rain out right now so will have to find a garage somewhere to check this out.. it is driving me crazy I cannot find a vac leak... The tps that I found that was just kinda swinging around wouldnt have caused any drops in vac or boost right?
 
I can get into details but here is an overview of how to find a vacuum leak:

  1. Locate a shop with a smoke machine and have the do it for you.
  2. Use a propane torch and a rubber hose on the end. Here you must be careful...
  3. Do what Freddie did to my old T-Bird and spray things down with Starting Fluid. Problem is this can cause a fire. He actually set my T-Bird on fire with this trick...
:eek:
 
Back
Top