Hi all, I know that I am a newbie to the forums- but let me assure you I am no newbie to wrenching or Toyotas (ASE certified tech w/10yrs exp.). My problem lies with my 94 4runner V6 (3.0L 3VZ-E) and the fact that I can't get any more than 4in/hg @ idle. I have done everything I can do (replaced PCV & hose, disconnected and plugged brake booster, replaced other vacuum lines, RTV'd the plenum gasket, etc) and I still cannot get enough vacuum out of this rig!

I bought it with a blown headgasket, so I wasn't able to do any preliminary diag (since I couldn't run it for long). I had the heads surfaced and pressure checked @ the local machine shop and everything came back great. The truck starts, runs and drives ok (albeit the idle isn't very smooth and the power brake assist is nonexistent) but it will not generate the amount of vacuum it should.

I pulled the upper timing belt cover off just to make sure the cam timing wasn't off, and both cam marks line up with the ones on the cover with the crank notch sitting at 0 degrees (TDC). So I am completely at a loss. I tried the EGR valve manually with my vacuum pump/tester and it opens and shuts like it is supposed to and there are no audible (as a leak this size would have to be) leaks from the engine bay!?!

I thought it would be the brake booster, but even after disconnecting the hose @ the plenum and plugging it- I still didn't have any increase in vacuum! ANYONE HAVE ANY IDEAS? Your help would be more than appreciated! Keep on truckin' guys and gals...
~Matt from Albuquerque

 

There are vac hoses that run to the canister in the passenger side wheel well, and down to the diff. Very long and a perfect place for a leak to hide..

 

Have you checked to make sure your vacuum gauge is correct?

 

I actually just ran out and checked it with my vac pump/checker and they read the same, I will check those lines on the diff tomorrow! Good call on both guys, keep the ideas flowing.

 

How about a sucked intake manifold gasket? You won't hear a vacuum leak,but it will kill the hole only at idle. Cylinder balance test to find dead/weak cylinder. Kill spark or pull off injector harness.

 

what was your outcome??