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  1. #1

    Default Question about rebuilt engine

    I just rebuilt my 5.7 350 and I have some questions about it. Once i first start her up, the engine idles kind of roughly and the exhaust smells of gasoline. Once the engine warms up, the rough idle goes away, but the gas smell still persists. Any ideas on this? I have already adjusted the idle and messed with the timing some. I'm still thinking its a timing issue.

    93 k1500 5.7 350 tbi

    Forged flat top pistons
    edelbrock 3702 cam
    k&n cold air intake
    Hypertech Chip
    Holley 670 cfm throttle body
    Throttle body spacer

  2. #2

    Default

    IT sounds like it could be a timing issue. Have you tried adjusting the throttle? Maybe it's dumping too much fuel at idle and needs set back a bit. That could be causing a rough idle also because the air/fuel mixture is too rich with fuel.

    -Greg

    The fool learns not from the wise man, but the wise man from the fool.

    2004 Silverado 4x4 (Suzie)
    6" Fabtech Suspension Lift
    35" NITTO Terra Grapplers
    18" MB Wheels Predators
    Thrush Turbo Series Mufflers
    on true dual exhaust
    Grille by Option Racing

    1952 3600
    Finally getting torn down to the frame.

  3. #3

    Default

    Yeah I have tried adjusting the throttle. Its weird because it like starts to cut out once you get into the higher rpms when its a little cold, but like I said once it warms up this is not an issue. I suppose i should try using a timing light to get it just right.

  4. #4
    Legend

    Join Date
    Feb 2008
    Location
    Red Wing, Minnesota, United States
    Posts
    3,356

    Default

    it could also be the coolant temp sensor, if they go bad it can cause the computer to dump fuel in at start up to the point of flooding the engine
    99 K1500 Suburban LT "THE BEAST"
    Hypertech III, K&N, true dual
    285/75/16
    ___________________________
    Jason

  5. #5

    Default

    Pretty much all of my sensors are new. The temp sensor is the newest one I have replaced.

  6. #6
    Sr. Mechanic Gambit's Avatar
    Join Date
    Feb 2010
    Location
    VA Beach for now
    Posts
    189

    Default

    You may want to check the spark plugs. Just becasue they are new doesnt mean they cant fail. if you have the smell of gas in the exhaust it could be becasue it isnt being burned.
    Jeep Recovery Vehicle.

  7. #7

    Default

    Tested all of the spark plugs and they are good as well as the wires. I guess the only thing it could really be is timing.

  8. #8

    Default

    You say it was a rebuild...

    How many miles were on it?
    Still have the stock Intake Manifold?
    Stock Exhaust Manifold or Headers?
    Still have the CAT's?
    Did you give the throttle body a good cleaning?

    Setting the Timing is a must. Also check the Idle Air Control Valve. Clean it for sure, but for $20 you can replace it.

    I did a rebuild, and I still can smell some gas in the exhaust. But that is cuz' I cut off the CAT's and the Dual Exhaust dumps out just behind the cab.
    Pavement sucks... :grrrrrr:



    1994 K1500 4x4 Ext. Cab
    PCM chip and Xenon 8000k bulbs
    350cu.in bored over .050"
    balanced Crank, 10:1 compression
    Flat top pistons,cam,ported heads
    Option Racing Cold Air Intake
    Holley Throttle Body Spacer
    Accell Igition, 45kv coil
    FloTech Headers, no CATs, dual exhuast
    Goodyear Silent Armor A/T 305/70-16
    Pioneer SupertunerIII CD USB Bluetooth
    Kicker ZX200.2 ZX Amp
    Kicker Audio COMP 10" Subwoofer

  9. #9

    Default

    Quote Originally Posted by ejohnson03 View Post
    You say it was a rebuild...

    How many miles were on it?
    Still have the stock Intake Manifold?
    Stock Exhaust Manifold or Headers?
    Still have the CAT's?
    Did you give the throttle body a good cleaning?

    Setting the Timing is a must. Also check the Idle Air Control Valve. Clean it for sure, but for $20 you can replace it.

    I did a rebuild, and I still can smell some gas in the exhaust. But that is cuz' I cut off the CAT's and the Dual Exhaust dumps out just behind the cab.
    How many miles were on it? Well like 135,000 and I blew some piston rings which messed up one of the cylinder walls so I had to rebuild to whole thing. Brand new everything.. The block was bored out, brand new forged flat top pistons, gaskets, rings connecting rods, cam......etc. I put a new intake on it. I still have the exhaust manifolds on it. Never had cats just the dual exhaust. Throttle body is a pretty much brand new holley 670 cfm and I did clean it. I do not know about the Idle Air Control Valve I will check that for sure.

  10. #10
    Sr. Apprentice
    Join Date
    Dec 2009
    Location
    Seabrook Texas
    Posts
    33

    Default

    Are you getting any codes to indicate that it is rich or lean? Usually if your far enough out of tolerance to smell gas its popping a rich code for sure?

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