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Old 07-21-2010, 10:41 AM   #1
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Default FAIL. Need NB help

Im at a loss at this point. We just put a 94 block in and my rebuilt MSM head back into my car. We've done the timing belt twice and both times it was fine. The problem Im having is that my idle is low around 950 to 800 and it bounces to a light degree. I now have 800cc injectors that arent really dialed in yet but this is the kicker; my HG's are at 10, but my afrs are normal around 14.7-15.2 at idle. I have no vacuum leaks that I can find. I sprayed carb cleaner all around the motor trying to find a leak and nothing. I figure at 10hg, that has to be one hell of an obvious leak.

The motor isnt smoking at all and it drives just fine actually. ITs the idle thats completely jacked up. Ive asked Jeremy from FM to help with the fuel settings for the injectors so hopefully he gets back with me today. Im using a Hydra BTW.

Any suggestions cause between Phil, Neogenesis, The Brain, and myself we couldnt figure it out lastnight
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Old 07-21-2010, 10:43 AM   #2
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i asked what kPa you were idling at yet you continue to give me ~hg.
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Old 07-21-2010, 10:48 AM   #3
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i dont know much about your build mate but i have seen this sort of problem so many time before and so many times when people take engines out and stuff they put the back in forgetting to reconnect all earth or have sprayed over the metal so earths are not good enough. im sure u already know but an earth is more important than a live. caught me out twice i know that, first time was a low idle and the second time it was hunting(idle control valve was a point of earth contact and it had been sprayed)
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Old 07-21-2010, 10:48 AM   #4
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Also, we cant adjust the idle through the throttle body screw. no matter how much we turn it, the idle wont budge.
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Old 07-21-2010, 10:49 AM   #5
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i dont know much about your build mate but i have seen this sort of problem so many time before and so many times when people take engines out and stuff they put the back in forgetting to reconnect all earth or have sprayed over the metal so earths are not good enough. im sure u already know but an earth is more important than a live. caught me out twice i know that, first time was a low idle and the second time it was hunting(idle control valve was a point of earth contact and it had been sprayed)
The grounds are fine. Ill check em again though later on this afternoon. Thanks.
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Old 07-21-2010, 10:51 AM   #6
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does it otherwise perfom ok or is there problem through out the rev range
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Old 07-21-2010, 10:53 AM   #7
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are you using a fuel presuure regulator. i have plumbed that backwards before and it would start but could only just idle.
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Old 07-21-2010, 10:53 AM   #8
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does it otherwise perfom ok or is there problem through out the rev range
It drives damn near perfect through the revs, with proper tuning it would be perfect. All the problems we're having are at idle.
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Old 07-21-2010, 10:53 AM   #9
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Ah another thing, and this is important, we checked the timing on the crank and the two marks were bouncing around. I still think its a timing issue but im not for sure.
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Old 07-21-2010, 10:54 AM   #10
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are you using a fuel presuure regulator. i have plumbed that backwards before and it would start but could only just idle.
No.
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Old 07-21-2010, 10:54 AM   #11
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i am basing my help on another make and type of engine but do you have idle control valves on 5's
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Old 07-21-2010, 10:54 AM   #12
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Ah another thing, and this is important, we checked the timing on the crank and the two marks were bouncing around. I still think its a timing issue but im not for sure.
Your timing was bouncing between 8-12 degrees, but that might just be because your revs were hunting.
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Old 07-21-2010, 10:56 AM   #13
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NB should never be bouncing. fix the timing belt and youll get your vacuum back.
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Old 07-21-2010, 11:02 AM   #14
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ok
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Old 07-21-2010, 11:03 AM   #15
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Quote:
Originally Posted by leatherface24 View Post
Also, we cant adjust the idle through the throttle body screw. no matter how much we turn it, the idle wont budge.
this suggests a hefty vacuum leak post tb
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Old 07-21-2010, 11:21 AM   #16
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there really isnt much that can leak post throttle body
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Old 07-21-2010, 11:23 AM   #17
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a leak post TB would increase the rpms significantly...even more so if you opened up the bypass valve.
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Old 07-21-2010, 11:24 AM   #18
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Old 07-21-2010, 11:30 AM   #19
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What about the timing mark on the crank? I know they LOVE to slip a tooth or two when your sliding the t-belt over that last idler pulley. When I did mine, I actually had to turn the crank about 1 mark clockwise so that when I put tension on the belt to slide it over the idler, it would align the marks properly. Just a suggestion though.


What's your vacuum on decel?

Does the sound of the exhaust at idle change from a lump to a purr to a lump as if the car were 'cammin' hard? Does it stall if you decel and push the clutch in or free rev it and let the RPMs drop?
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Old 07-21-2010, 11:34 AM   #20
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Quote:
Originally Posted by leatherface24 View Post
there really isnt much that can leak post throttle body
Quote:
Originally Posted by Braineack View Post
a leak post TB would increase the rpms significantly...even more so if you opened up the bypass valve.
ok I give up lol
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