Thread: vacume is low...out of ideas

You said you replaced your intake manifold? What about your IM gasket? Fuel rail grommets set so you're not leaking air from injector ports?

Go over everything with brake cleaner? Notice a change in your idle at all when you used it?

yeah, tried that. thought for sure it was the manifold gasket, because i had reused the metal one. so i made a new one out of gas proof gasket maker(the rubber kind) and installed it along with a new throttle boddy gasket. no chnage. so then we sprayed brake cleaner on the injector seal like you suggested......and nothing happened. so the ONLY thing i cant check EASILY is the vacume lines under the manifold.....but i checked them really well before i installed the motor. since then ive checked them probably 10 times. im going to TRY resetting the iacv, but i dunno. hey, whats the vacume supposed to be at say 5000 rpm in neutral? i think mines in the 23 hg in area.....

and i already grounded my maf.......it was a precaution a while ago.....i checked the maf readings today, ran the fans over it. the voltage is currect, its reading properly.

So exactly what all did you switch over?

A wrong sensor sounds like a good bet, as well as bad wire. I would go over each connection for each sensor and unplug one at a time to rule those out.

How old is the head, is there a lot of carbon build up, that could be an issue also

the motor is fresh. the head is just as old as the block. no carbon buildup. everything from the one motor went on to the other, the whole point being to avoid this exact problem. wiring is good. can a bad iacv cause low vacume?

and when i give it a few hundred rpm above idle, vacume seems to be right. its just at idle.....maybe the iacv CAN do this? i dunno. any thoughts?

I know the IACV is nuts and can cause all sorts of unpredictable stuff. If you're completely out of ideas, i'd pull the iacv and check it for buildup, clean it up,check the gasket, etc. That will also give you the chance to reset it. I'd def go over grounds and connections and maybe test the resistance on the water temp sensor.

ok. one more question. when i set my timing, i found i had one more timing mark than i expected (its an avenir motor) is there a diffrence between a avenir crank pulleys timing marks and a usdm? i still think its set right, just trying to find out if there IS a diffrence. pulley was kinda beat up, hard to read it at first. i have read a few other posts, and other people SEEM to have trouble like i am that sounds the same. im just not sure about the low vacume part at idle. maybe my idle is just low, and the tach is REALLY off. ill be resetting the idle air valve tomorrow, along with idle and checking timing. because i dont think this is a REAL vacume leak, i cant see how it could be, ive checked everything.

The Idle Air Control Valve can screw all kinds of things up at idle if it is messed up. Not sure on the avenir's crank pulley, but if it's anything like the GTi-R's it goes -5; 0; 5; 10; 15; 20. I really don't think you have a vacuum leak either and that one of your sensors or something is causing this.

yeah.....the more i think about it its got to be some sensor. how about this food for thought....is there a idle point where vacume would be low? because if i give the car about 200 rpm the vacume is where it should be.....i will reset the iacv tomorrow, its the only thing ive messed with since the install. so MAYBE the idle is actually just set 200 rpm to low.....maybe that sounds dumb, its just a thought. ill look at it all in the light tomorrow. If the timing is like the gtirs, im at 15 degrees then.