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Discussion Starter · #1 ·
So, yesterday I installed a FAST intake on an LS1 and on the drive home the car started surging real bad (vacuum leak?), but this was after 1.5 hours of driving. Then I pulled over and shut it off, then when I fired it up again the RPMs went to 4,000 (to the factory limiter in park) and would not come down. Do I have a massive vacuum leak or did some sensor come loose? If you guys have any ideas of things to check out, let me know. Do you think the actual bolts that hold it down could have come loose? I will probably have to take the thing off again....
 

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I doubt the bolts came loose, any vacuum leak will cause the throttle to come up. First make sure the throttle blade isnt hanging up, then make sure the MAP sensor didnt fall out on the back, then make sure all the hoses are connected.

Its also possible the IAC motor is stuck, its really kinda hard to screw up an LS manifold install if you used a torque wrench and nothing is holding it up off the heads.
 

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Discussion Starter · #3 ·
Wow, now that I think of it, the MAP sensor was a bit loose. That may be it, thanks!!
 

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if you swapped over the factory IAc, I wold spray it out with carb cleaner and try again. The other way to check for leaks is to take a spray bottle with water in it and start spraying the manifold with a mist. the water will temporarily make the idle drop.
 

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Did you seal the intake halves with silicone ? They are very very prone to leaking.
 

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I'd check the MAP sensor first, that would be the most likly culprit IMO. After that the hookup's for the pcv, that stuff.

I have heard of one instance of the 2 halves leaking, and have seen people forget to put the short in to hold the valley cover on and the intake won't seal correctly because of this, but that's kind of an obvious problem when installing the intake IMO.

As PSJ mentiond if you have an older fast TB, that could be hanging up. If that's what you have for a TB, go turn it in for scrap alum, and get any one of the other TB's out there that are 90mm (nick williams, edlebrock, wilson, bluemaxx, any of them they all work fine)
 

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Discussion Starter · #8 ·
I checked all the connections yesterday with no results. If it was sticking you should be able to manually close it right, but the rpm doesn't change when we try. The DiabloSport Predator says we have a Mass Air Performance error/out of range problem. I guess the halves could be leaking and we didn't use silicone. I'm going to have to mess with it when I get back from NMCA Milan...
 

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Put a scanner on it and if the Ltrims are like -25, it's super lean and the correct is maxed out. That would signal a tune issue or a non-sealed intake.

Cars will run with the MAF unplugged to that's an easy test.
 

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Discussion Starter · #10 ·
These are the codes the Snap On diagnostics tool showed:

P0101 -mass air performance/out of range

P0108 -MAP code

P0341 - CMP Sensor Out of Range.
 

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Discussion Starter · #12 ·
Okay, thanks.
 

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Some of the early FAST 90mm TB's would stick and could sit at 4 grand like you are saying.
i tried 4 of them before i gave up and when to a holley 90 ?

i dont know how the new batch of fast t/b's stack up

Thanks

Nick--
 

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Discussion Starter · #20 ·
Ha ha, not yet. I'm not really looking forward to pulling it off. I'll probably work on it on Thursday....if I can get 20 pages turned in for the mag by then. LOL
 
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