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95 Z71 Losing power

This is a discussion on 95 Z71 Losing power within the Technical / Maintenance forums, part of the General Discussion category; I am quite new to this but I need help. I have a 95 Z71 Silverado 5 liter tbi. On ...

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    95 Z71 Losing power


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    I am quite new to this but I need help. I have a 95 Z71 Silverado 5 liter tbi. On start up it idles ruff like its missing the colder the air temp the worse it runs. As the engine heats up it gets better but never great. If you floor it at idle or 60 mph it just goes flat and loses power BAD! It reminds me of an open choke on a cold boat motor, it runs just no power. As long as ur gentle on the throttle it runs fine. This just started out of nowhere and the fuel milage has went to total crap!! Along with all of that it has stopped shifting on its own (auto trans) you have to let off the throtytle and it shifts fine. Any help at all would be a life saver. Thanks

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    Re: 95 Z71 Losing power

    Update!! While looking for the engine stamp to confirm engine, I found a cracked exhaust manifold. I am sure this isn't the main problem, but how big of a problem is this?

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    Re: 95 Z71 Losing power

    Anyone's opinion would be much appreciated. I have concluded that it is a lack of air problem. Im thinking maybe air/idle control, vaccum, O2 sensor. Advice on where to start?

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    Registered User Midwest Militia's Avatar
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    Re: 95 Z71 Losing power

    Sounds more like your timing is off.


    92 Silverado ECSB TBI 5.7, 4L60, Limited Slip, AC Delete, Edelbrock Air Cleaner, True Dual Straights, Toolbox, Debadged, Cragar Soft 8s, replacing everything one part at a time...

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    Loves GMT400 haters someotherguy's Avatar
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    Re: 95 Z71 Losing power

    Check timing, check fuel pressure, and replace the exhaust manifold if it's bugging you.

    If it's the passenger side one (most likely) you'll need to buy one new, or spend a lot of time hunting boneyards because it's frequently broken, right at the curve off the #2 cylinder. Often hidden by the heat shield, unless you happen to find a truck that isn't equipped with the heat riser setup, like the '95 3/4 ton I pulled my air cleaner housing from.

    Richard

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    Re: 95 Z71 Losing power

    I was just wondering how important that crack was? It is not big but there are 2 of them. They are both on the driver side 1 at the base of the #1 and 1 at the base of the #4.

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    Re: 95 Z71 Losing power

    This is bugging me. I am replacing the cap and rotor and plugs and wires. I cannot find any vac leaks and havent check fuel pressure yet. I was thinking maybe restricted fuel flow, but the filter is supposed to be non serviceable because its in the pump in the tank. Anyone know anything about that?

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    GMC RULZZ NEUMANNZZ's Avatar
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    Re: 95 Z71 Losing power

    fuel filter should be on the inside frame rail under driver side door. its replaceable.
    O2 GMC RCSB 4.8L V8 AUTO 3.73's
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    G-FORCE FinalBreath's Avatar
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    Re: 95 Z71 Losing power

    Quote Originally Posted by neumannzz View Post
    fuel filter should be on the inside frame rail under driver side door. Its replaceable.
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    Re: 95 Z71 Losing power

    Can anyone tell me if the engine is supposed to rev up when you unplug the throttle position sensor?

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    Re: 95 Z71 Losing power

    Can anyone tell me if the engine is supposed to rev up to around 1100 rpm when u unplug the throttle position sensor. Is this normal?

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    Re: 95 Z71 Losing power

    I have a 94 z71 and recently had the same problem with my truck. I replaced the fuel filter(which like dude said earlier was under driver side door) didn't help. I replaced the O2 sensor because i was getting a lean exhaust code. that neither cleared the fault nor fixed the problem. I replaced the Idle Air Control Valve, no change in the performance. I replaced the TPS and it cleared the fault, truck still ran like a pile. finally dropped the tank and replaced the fuel pump/sender/ ect. it cost me a pretty penny but it fixed the issue.

 

 

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