Car is a M6, 383 with a Bret Cam. Car should be making 12-15 in HG at idle, and we are only seeing 7-8 in HG. The car is idleing at about 850, with 25-29° of timing. Car has new PCV valve, and the rockers are adjusted to 1/8th past zero lash (stock lifters). Where else can I look?

 

ARe you sure there is not a leak someplace?

Do you know what the idle vacuum is at 1000rpm?

Bret

 

Bret I dont know what it is at at 1000rpm. The car was idleing at 950 and was idleing at about 65-67 kpa. I lowered the idle to 850, and its now idleing at 74-76 kpa. Im thinking she might need to idle at about 950-1000? To get proper vacuum?

 

Try blocking off all the vacuum sources on the manifold (i.e. brake booster, FPR, EGR, Interior vacuum feed, etc) and see if that imrpoves vacuum. This way you rule out a leak from an "accessory".

 

yeah and make sure the one under the TB is plugged as well.

bret

 

TB is plugged, two vacuum ports on passanger side are plugged, and I disconnected the brakes, and still idleing in the 63-67kpa. I also pulled the pcv valve and its working fine. Is 63-67 kpa what its suppose to be idleing at? What else could I do?

 

under the tb? there is a vaccum line under the throttle body?

 

There is a port under there that leads into the IAC passages.

A low idle vacuum can be due to bad valve adjustment too, going to zero lash can help as well.

Bret

 

Quote: "under the tb? there is a vaccum line under the throttle body?"

This is the vacuum source for the PCV valve.

 

wait a minute? my pcv valve just makes a "u" and goes right back into the manifold in th fitting right next to the pcv...

 

Its routed a little different in 96-97 LT1s but I believe there is still that port below the TB so while I cant think where it goes right off the top of my head, you cant miss it just reaching down under the TB.

 

If you have a 95 intake your PCV valve routes to under the TB; I know the 93 intakes had the U turn PCV connection. Your signature states that you're running a 1995...I assumed the intake was original.

 

I dunno... maybe its only 93 and 94 LT1s that had it routed like that.

 

the car is a 1995, but the motor came out of a 1993. The front port is plugged, and the pcv is in the u turn, but that shouldnt make a difference correct?

 

I readjusted the rockers, and still no luck. I plugged all the vacuum ports on the manifold, and still had no luck. What should I do now?