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Thread: vacume is low...out of ideas

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Posts: 1-10 of 48
2008-10-24 19:47:48
vacume is low...out of ideas
i have a 92 nx 2000, avenir motor, jim wolf ecu, 8.5 to 1 compression, 50 pound hr injectors, cobra maf. i had this setup running fine on a diffrent motor, but i replaced it with the one thats in there now. bought the motor from keo, had to install cams(had no trouble there, timing is set right), fired up the first time, but its only got 10 pounds of vacume, no matter what i try. i had install the intake manifold on to the avenir motor, ive checked the vacume lines on the back of the manifold over and over, pressure tested it, replaced the intake manifold gasket and throttle boddy gasket....and it STILL screwed up. idles rough like its got a heavy cam profile (it doesent) and runs like crap. its really rough, choppy, broken up before 3000 rpm.....it smoothes out abrumptly when you hit 3000, but its SLOW. i have no idea. ive tried EVERYTHING. i checked the maf, its fine. i even ran the maf blow through to see if it was a boost leak, nope. thats not the problem. maf is currently ON the throttle body, and its STILL 10 pounds of vacume, idles rough, has no power, EVEN when i put the gauge under the hood. no vacume leaks i can find......everything is nice and tight. what could possibly cause this? everythings the same, just a diffrent longblock i transfered my manifold and cams to. sensors? i dunno, i need help here. ive tried EVERYTHING.
2008-10-24 20:53:05
Check your ignition stuff plugs, distributor and all that stuff. PVC valve if it hasn't been replaced lately

Are you seeing an oil leaks any where? When you pinch the hose going from the PVC valve to your intake manifold what happens any change?
2008-10-24 21:02:40
What's your A/F at idle? Does consult tell you anything? What RPMs does she idle at? Bigger cams will drop you vacuum some, but no where near that much. You mean 10inHG not 10psi, correct? Have you made sure you actual timing is correct (like set it in timing mode with a gun)? What about adjust you IACV? These are all things that can effect your idle and vacuum.
2008-10-24 21:13:03
yeah i know all this. i dont have a wideband hooked up. ive checked all the basics, this is NOT an easy problem, its been this way for 2 months. everything is perfect. plugs are bkre7s, gapped at .025, the pcv valve is new and anyway, when i block it off from vacume it still doing the same thing. no check engine lights, i dont use the consult plug, this is a basic swap. stock cams, STOCK CAMS. yes, not 10 pounds of boost, 10 pounds of vacume. this is my 4th turbo sr20det car, probably my 10th turbo car in general. i have tried EVERYTHING. there is NOTHING i can think of at this point. it setup na, with stock timing dead on, with stock cams, maf is working pefect, and its only running 10 pounds of vacume.
2008-10-24 21:20:05
10 lbs of vacuum? Do you mean 10 in Hg? 10psi is 20.36 in Hg... Normal vacuum is 16-18 in Hg IIRC
2008-10-24 21:25:11
You SURE your cam timing is correct? That can definatly cause it...why did you have to swap stock cams back into it?
2008-10-24 21:50:45
Welcome to the club.

I've had this problem since I first turbo'd my SR20DE, and still have it with my DET build.

It's annoying to say the least, but doesn't really affect driving the car. Just the idle.
2008-10-24 21:52:51
Originally Posted by wnwright
10 lbs of vacuum? Do you mean 10 in Hg? 10psi is 20.36 in Hg... Normal vacuum is 16-18 in Hg IIRC

im not here to nit pick, 10 vacume on the guage. its supposed to be 18. im not here to debate. and ive tried multiple gauges.
2008-10-24 21:59:10
Originally Posted by TeKKiE
Welcome to the club.

I've had this problem since I first turbo'd my SR20DE, and still have it with my DET build.

It's annoying to say the least, but doesn't really affect driving the car. Just the idle.

no, it does. im going to come across as an ass, cause im tired and worn out. please dont take it that im TRYING to be an ass. it just i keep hearing the same simple ideas over and over. it runs like crap. not just at idle, but all the time. 8 pounds vacume, or whatever the hell the dude above wants to call it is a HUGE leak. NO a timing issure with STOCK cams will not cause this.....i dont care if its a tooth off. both Jeong and i set the timing. the reason i put the cams in were BECAUSE THERE WERE NO CAMS. i put that in caps so everyone would see that. i put STOCK cams in, set it to base timing but using a screwdriver on #1 piston, and turnind the crank over to tdc. i then proceded to set timing as written up on this forum. its NOT THE THE TIMING. again, im not trying to sound like an ass, its just i keep hearing the same thing, even though ive already said ive covered it. i dont know, i really give up at this point.....
2008-10-24 22:22:17
But there are things we have said that you haven't and cant check:

If you are running lean then you vacuum will be low and your car will run like ****. The diffrance between a 15 A/F and a 18 A/F is about 3 inHG. If you take into acount that some engines just sit at 16 inHG and you are running lean the that would give you a crap-tastic vacuum.

And just because you don't have a CEL doesn't mean everything is hunky dory with the ECU. hooking up a consult would let you look at things, like what timing your ECU thinks it's at. Worse case, your crank pulley could be old and the inner rubber lining could have given way and you timing setting could be way off.

If you checked and are sure you MAF, IACV, AAC, FICD, TPS, injectors, ignition system, and BOV are all working 100% correctly and you know you don't have a vacuum or boost leak because you presure checked, then there is not much more it could be.

What's you CR on all four? Did you switch all sensors over from the old engine to makes sure all the sensors match the ECU? You really need to find out what A/F you are running and see what the hell your ECU is thinking, IMO. These are two things you have no idea about that effect this issue.
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