after replacing parts, still missing/bogging/low idle
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The correct fuel pressure for an LT1 is 43.5psi, with the vacuum line removed from the fuel pressure regulator. GM accept anything in the range of 41-47psi (+4%/-3% flow). Reconnect the vacuum line and the pressure will drop 6-8psi with a stock cam. It should hold the "no vacuum" pressure at WOT.
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Joined: Feb 2004
Posts: 1,736
From: Reidsville, NC
opti
water pump with new sensor
plugs
msd wires
coil
both o2 sensors
knock sensor
IAC
TPS
IAT
ICM with cooling mod
fuel filter
*checked egr valve and seems to be working properly so now im leaning towards something on the fuel side, possibly the FPR...
*swapped MAF with another car and doing the same thing also
Last edited by groundpoundinlt; May 4, 2008 at 10:58 AM.
Thread Starter
Registered User
Joined: Feb 2004
Posts: 1,736
From: Reidsville, NC
The correct fuel pressure for an LT1 is 43.5psi, with the vacuum line removed from the fuel pressure regulator. GM accept anything in the range of 41-47psi (+4%/-3% flow). Reconnect the vacuum line and the pressure will drop 6-8psi with a stock cam. It should hold the "no vacuum" pressure at WOT.
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Joined: Feb 2004
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From: Reidsville, NC
i replaced the fuel filter also...need to add that to post above...i can get a regulator for less than $35 but your right it could be the pump...whats the best way to determine if its the regulator or the pump after a pressure test??
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From: Reidsville, NC
well after digging up old threads, i pretty sure i have a fuel issue with either the pump, fpr or a leaky injector...some symptoms i was and still am having are hard starts (almost free spinning) white smoke first few minutes of idle, strong smell of fuel out tailpipes, and backfiring in the air intake which from what i read are all fuel issues...im still trying to find a buddy with a fuel pressure gauge so i can check the pressure during start, idle, etc...just trying not to buy parts i may not need...
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From: Reidsville, NC
edit: borrowed a fuel pressure gauge from a buddy at work and when turn the key to on, without starting goes to 40-45 and stayes ther at a constant...car has been running for about 10min now and constant pressure between 40-45...the longer the car runs, the worse the idling and bogging gets...could the MAP sensor possibly be my problem or maybe the PCM??
Last edited by groundpoundinlt; May 10, 2008 at 05:23 PM.
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From: Dayton, Ohio
Go to the parts store and get a stethoscope and listen to your injectors one at a time. Just place the steth on the body of the injector and listen. You should hear a nice clicking noise. If you don't then it's a bad one. And also test the vacum on the car while it's running. A vacum test can be really helpful in telling you what's going on with your car.
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Joined: Feb 2008
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From: Dayton, Ohio
15 - 20 in hg is a good basis. I'm not sure what it is exactly for an lt1. Just note the in. hg. and what the needle on the gauge is doing, i.e. staying steady, rising, dropping, vibrating, ect. Test is at idle and under load (W.O.T.)
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My car is doing that same thing... Runs fine for a bit, then starts missing bad, and at about 2500 rpm, it kicks in fine. Its really hard to stay at a steady speed... And when I check my OB1, or try to, the electric fan kicks in? Why is this?