4.3 tbi has a drinking problem..

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ottomilio

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Hi,
I’m new to this forum but some help would be very much appreciated.
My K1500 is from -92 with 170k miles, the truck’s been sitting a lot since the last 10 years..
It runs very rich and tailpipe is black with soot.
Gas mileage is never above 10mpg.

Truck runs very good when cold, but the check engine light comes on and disappears when engine gets warm, code 13, O2 sensor, it also runs sluggish at idle and low speeds when engine is hot. Never stalls

Sparkplugs, rotor, cap, and O2 sensor are replaced recently.
Everything else is probably original.

Any advice on what to look for, to lower the trucks drinking problem a bit..?

Also any advice on a good scan tool so I can read the data, and where to find the right values for the different sensors?

Thanks!
//Otto
 

SAATR

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No recent experience with OBD1 scanners so I can't comment.

Truck is definitely definitely over-fueling and causing your rich condition. The engine computer's coolant temperature sensor would be my first stop in diagnostics. They have a tendency to get stuck in the cold range when they go bad. They are a resistive type sensor that can be checked with a multimeter. Specs should be available with some searching. Live data would be the best way to confirm, obviously.

Beyond that, TPS and MAP can contribute to fueling problems, as well as faulty pressure regulators or injectors. Start with checking the CTS and see where you end up.
 

L31MaxExpress

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The TBIs are bad about the base gasket under the TBI turning to mush and then they leak vacuum which effects the MAP sensor reading. With less vacuum the MAP sensor falsely translates it to the engine being under more load and the TBI dumps more fuel. Change out that base gasket. Its cheap and can cause alot of problems. Also check the rubber fittings and nylon tubing between the MAP and TBI for cracks, splits and loose ends that can allow a vacuum leak.
 

thx1138v2

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Replace your coolant temperature sensor (CTS). It's the one on the intake manifold in the front of the engine near the radiator hose attachment point. It's only about $12 so that's a quick and cheap fix, if that is the problem.
 

ottomilio

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UPDATE:
Replaced CTS, and base gasket under the TBI. Problem is still there..
White smoke, and tailpipe is really black. Horrible gas mileage.
Any help?
Thanks!
 

RichLo

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Check fuel pressure and look at the injector spray pattern. They should both be nice even cones of fuel spray with no large drops coming out.
 
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