Low Vacuum?

[johnfsmith]

I've just got my new motor and trans all in and running good but I've noticed the vacuum at idle is reading -8. I've done a pressure test and found no leaks(holds 20 psi). I've also done a compression test reading 160 across all four. My mods are in my profile... Should I be reading more? If so what else should I check?

Thanks,
John

 

[DSM90AWD]

I would definitely start by checking your cam timing.

Using a long screwdriver in the #1 cyl plug hole, turn the crank pulley (car in neutral of course ) until the screw driver is at the top of it's travel and the Cam pulley dowels are at 12 o'clock.
The cam sprocket timing marks should now be facing each other at 3 and 9 O'Clock. Use straightedge to verify they are aligned exactly. Now look at the crank pulley timing "notch". It should be exactly at TDC on the lower timing cover's scale.

If either are off you need to re/re the timing belt

 

[ddavisaf]

How long did you hold 20 psi during your boost leak test?

 

[johnfsmith]

I would definitely start by checking your cam timing.

Using a long screwdriver in the #1 cyl plug hole, turn the crank pulley (car in neutral of course ) until the screw driver is at the top of it's travel and the Cam pulley dowels are at 12 o'clock.
The cam sprocket timing marks should now be facing each other at 3 and 9 O'Clock. Use straightedge to verify they are aligned exactly. Now look at the crank pulley timing "notch". It should be exactly at TDC on the lower timing cover's scale.

If either are off you need to re/re the timing belt

I just checked the timing and it checks out ok.... any other suggestions? And it held 20 psi for 30 seconds and it didn't drop at all so I didn't think that would be a problem, how long should it hold for?


Thanks

 

[ddavisaf]

Boost leak test is perfect.
Timing is good.
Compression is good.

Where is your boost gauge tee'd into?

 

[johnfsmith]

Boost leak test is perfect.
Timing is good.
Compression is good.

Where is your boost gauge tee'd into?

Tee'd in at the fpr

 

[johnfsmith]

Found the problem, my pressure sensor is going bad. I hooked up my old boost gauge and it's -20 at idle.

Thanks for the help.

John