LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

Possibly a fuel pump?

Old Nov 24, 2008 | 05:29 AM
  #16  
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From: Hell was full so they sent me to NJ
The idle number is difficult to evaluate, since you don't indicate whether you have an A4 (stock = 550rpm in gear) or an M6 (stock = 800rpm). Why not include that basic info in your signature?
Old Nov 24, 2008 | 10:57 PM
  #17  
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its a M6 tranny
Old Nov 26, 2008 | 07:54 PM
  #18  
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nothing?
Old Nov 26, 2008 | 08:06 PM
  #19  
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Stock M6 idle, fully warmed up, is 800rpm. But the stock tach typically reads 100-200rpm high, so your 1,000rpm sounds OK. On cold start, the PCM elevates the idle speed, baqsed on coolant temp. At -40*F the idle is 1,200rpm; at +24*F idle is 1,000rpm; at 111*F it drops to 800rpm. So an elevated idle on cold start isn't unusual.

Similarly, the PCM elevates the idle speed until the vehicl comes to a complete stop (VSS = 0mph). What yours is doing doesn't sound unusual.

Losing all the fuel pressure in 45 minutes is enough to make it hard to start. Could be:
-leaking injectors (does it start easier if you hold the accel pedal on the floor when you try to start it = clear flood mode?)
-leaking fuel pressure regulator (is the vacuum line for the regulator wet with fuel?)
-leaking check valve in the fuel pump (hard to diagnose, and requires full replacement of fuel pump to correct)

Last edited by Injuneer; Nov 26, 2008 at 08:12 PM.
Old Nov 26, 2008 | 09:31 PM
  #20  
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just went out there and tried starting it with the pedal to the floor didnt help. so leaky fuel injector is out i'm waiting to see if fuel seeps to the vacuum line in the next 30-45 minutes. i appreciate all the help man. not having the proper tools kinda makes it hard to do this stuff but now that u kinda gave me something to inspect easily i might be able to go about this by process of elimination.
Old Nov 26, 2008 | 10:15 PM
  #21  
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nope vacuum hose is dry too.
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