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1995 Chevy TBI running rich....Please Help

This is a discussion on 1995 Chevy TBI running rich....Please Help within the Technical / Maintenance forums, part of the General Discussion category; I have 1995 Chevy Truck with a TBI 305. It has the following: 1. TBI Spacer with a notch between ...

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    1995 Chevy TBI running rich....Please Help


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    I have 1995 Chevy Truck with a TBI 305.

    It has the following:

    1. TBI Spacer with a notch between the bores
    2. Injector Pod Spacer
    3. Adjustable FPR (set at 13 PSI)
    4. Power Charger Bowl
    5. Shorty Headers
    6. 3" Exhast w/ a D-max Bullet
    7. 160 Degree Thermostat

    Right now I have a Code 45 (Rich Exhaust), and Code 33 (error in the MAP sensor signal). The engine is running rich.

    I plan to the following:

    1. Replace MAP Sensor
    2. Inspect ALL Hoses on top of the engine for cracks
    3. Replace O2 sensor of necessary.

    Anything else I should try?

    The truck has 317,000 on the original motor. All of the hoses on top of the motor replaced roughly a year ago. For the passed year, the truck has had regular Seafoam Treatments as well.

    Thanks.
    Last edited by axisT6; 08-22-2007 at 08:22 AM.
    1995 Chevy Extended Cab 2wd: 14 FF, HSR 406, NV4500, Solid Front Axle

  2. #2
    GMC RULZZ NEUMANNZZ's Avatar
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    Re: 1995 Chevy TBI running rich....Please Help

    I would make sure your wires and connector going to the map sensor are okay. let us know what happens.
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    Re: 1995 Chevy TBI running rich....Please Help

    160 thermostat will make it run rich because the ECM never sees the engine as being warmed up or closed loop as the tuners call it.. Go back to the 180 thermostat and I bet it will go away.
    1991 C1500 Ext. Scrapped. I still have the engine, tranny and Detroit tru-trac.
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    Registered User Alexander's Avatar
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    Re: 1995 Chevy TBI running rich....Please Help

    Fix the problem with the MAP first, everything else is secondary. The map sensor is like the crystal ball for the PCM, and lots of weird things can happen if it's not working right. Also, no need to change the O2 sensors, they appear to be working (they told you you were running rich, right?)
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    Re: 1995 Chevy TBI running rich....Please Help

    Quote Originally Posted by TITANIUM
    160 thermostat will make it run rich because the ECM never sees the engine as being warmed up or closed loop as the tuners call it.. Go back to the 180 thermostat and I bet it will go away.
    I was afraid it may have been the T-stat. I figured 160 Degrees would be warm enough for the ECM to go to closed loop. What is the ideal closed loop temp?
    1995 Chevy Extended Cab 2wd: 14 FF, HSR 406, NV4500, Solid Front Axle

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    Re: 1995 Chevy TBI running rich....Please Help

    Quote Originally Posted by Alexander
    Fix the problem with the MAP first, everything else is secondary. The map sensor is like the crystal ball for the PCM, and lots of weird things can happen if it's not working right. Also, no need to change the O2 sensors, they appear to be working (they told you you were running rich, right?)

    I am going to replace the MAP first since the one on there is as old as the truck. Hopefully that will change something.
    1995 Chevy Extended Cab 2wd: 14 FF, HSR 406, NV4500, Solid Front Axle

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    Re: 1995 Chevy TBI running rich....Please Help

    Quote Originally Posted by axisT6
    What is the ideal closed loop temp?
    It depends on what ECM you are running.
    1991 C1500 Ext. Scrapped. I still have the engine, tranny and Detroit tru-trac.
    2005 GTO LS2 with full Pedders track II suspension. StreetsweeperHT cam with Kooks exhaust. Tuned.

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    Re: 1995 Chevy TBI running rich....Please Help

    Alright, the MAP sensor has been replaced, and the stock 195* T-stat has been installed. Still Rich.

    I am going to replace the Plugs, Wires, Cap, Rotor, and O2 sensor since they are about due. Hopefully this will result in a much better spark and AFR reading for the ECM.

    Based on the info in Post #1, can anyone else see any reason why I would be running rich? By the way, I have no vacuum leaks, and the only code I am throwing is CODE 45 (rich exhaust).
    1995 Chevy Extended Cab 2wd: 14 FF, HSR 406, NV4500, Solid Front Axle

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    Re: 1995 Chevy TBI running rich....Please Help

    I also discovered that the media inside the catalytic converter is loose and rattling. I am guessing that this is a result of the rich condition.
    1995 Chevy Extended Cab 2wd: 14 FF, HSR 406, NV4500, Solid Front Axle

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    Registered User young blood's Avatar
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    Re: 1995 Chevy TBI running rich....Please Help

    turn your fuel pressure down a little see what happens

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    Re: 1995 Chevy TBI running rich....Please Help

    I tried that, but it wont adjust below 13 PSI.
    1995 Chevy Extended Cab 2wd: 14 FF, HSR 406, NV4500, Solid Front Axle

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    Re: 1995 Chevy TBI running rich....Please Help

    computer will hit closed loop at around 100 deg F.
    can't turn it down below 13? huh.

    it might be the CTS in the manifold. those are pretty cheap, so I would throw a new one on. plus they're easy to change
    91 K1500 ECSB
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    Re: 1995 Chevy TBI running rich....Please Help

    Quote Originally Posted by 91chevZ71
    computer will hit closed loop at around 100 deg F.
    can't turn it down below 13? huh.

    it might be the CTS in the manifold. those are pretty cheap, so I would throw a new one on. plus they're easy to change
    The adjuster screw on my AFPR hits my fuel line right at the 13 PSI setting, thus, 13 PSI is as low as I can go.

    I am guessing CTS = Coolant Temperature Switch??

    Thanks.
    1995 Chevy Extended Cab 2wd: 14 FF, HSR 406, NV4500, Solid Front Axle

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    Re: 1995 Chevy TBI running rich....Please Help

    Anything that will cause your engine to flow less air in or out such as a clogged up air filter will cause a rich condition. A sticky injector will also do it.
    1991 C1500 Ext. Scrapped. I still have the engine, tranny and Detroit tru-trac.
    2005 GTO LS2 with full Pedders track II suspension. StreetsweeperHT cam with Kooks exhaust. Tuned.

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    Re: 1995 Chevy TBI running rich....Please Help

    Quote Originally Posted by TITANIUM
    Anything that will cause your engine to flow less air in or out such as a clogged up air filter will cause a rich condition. A sticky injector will also do it.
    I normally seafoam the truck both through the gas tank, and through the PCV hose. I would like to think that I don't have a sticky injector. The air filter does not need replacing yet.
    1995 Chevy Extended Cab 2wd: 14 FF, HSR 406, NV4500, Solid Front Axle

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    Re: 1995 Chevy TBI running rich....Please Help

    By tomorrow, I will have replaced the following:

    Stock plugs with Delco Rapid Fires with .054" gap

    Stock coil with MSD Blaster Coil

    Plug wires

    Cap

    Rotor

    Manifold Temp Sensor

    O2 sensor

    This better work!
    Last edited by axisT6; 12-21-2007 at 06:13 PM.
    1995 Chevy Extended Cab 2wd: 14 FF, HSR 406, NV4500, Solid Front Axle

 

 

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