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Old 03-16-2011, 02:50 PM
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Fuel efficiency out of 4.3 liter vortec impossible?

Hey guys. So my girlfriend just bought a really nice, excellent condition 1994 chevy S10 SS 4.3 liter vortec V6.



So the truck runs nice and has great power, but.......... the fuel economy is the absolute worst on ANY engine I have ever seen! My friends supercharged 502 big block gets better mileage than this 4.3 vortec!! I don't even think it is getting 5 km to the liter right now. The truck only has 190,000km on it, very low for a '94! So the previous owner installed a dual flowmaster exhaust, a K&N intake, and an upgraded "chip". Correct me if I am wrong but the only one of these I could see affecting fuel mileage would be the computer chip. I have heard these engines are terrible on fuel but I could have never imagined it would be this bad! Hard to believe a small or big block V8 makes MORE power and burns LESS fuel, imagine that! So is this just how these engines are? Is there any tricks you folks have used in the past to increase the fuel efficiency of these trucks? It is costing her $20 to go to work and back everyday right now. I`m even beginning to think that there may be a fuel leak or something because this is just wrong. Any tips or info you have is appreciated!

Keith

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Old 03-16-2011, 03:11 PM
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My wife's GMC Envoy has the same 4.3 v6 vortec which is rated around 175 horse power give or take a few and she gets around 19 mpg highway and 11-13 mpg town. I don't know why but those motors being as mild as they are should do more then that. I have seen many carbureted v8 chevys make better that. My 350 which has around 375 hp used to get around that before I had my cylinder heads done and such.
Eric
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Old 03-16-2011, 03:51 PM
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Bolt a TBI 305 in it. it will also need a new TBI, sensors and ECU ( 1 from a '94-'95 1500 truck with comparable trans should work ). I pull 16 MPG in the winter with my '95 K1500 ECLB W/ NV 3500 5spd. I can get 17-18 MPG on the highway in warmer months/ better gas. That's a 6,000LBS+ truck. The S-10 weighs in around 3,200 lbs

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Old 03-16-2011, 04:05 PM
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thats typical of a 4.3, better to smallblock it.
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Old 03-16-2011, 04:07 PM
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Unless someone swapped in a '96 or later 4.3 a '94 would be a "Vortec" in name only, it still has regular center bolt valve cover heads not true Vortec heads. Since it says "Vortec" on it though I'm assuming it's MPFI (multi-port injection) not TBI. MPFI had a lot of issues with intake leaks, the fuel ines to the injectors or "spider" in particular IIRC. That would be a good place to start checking.

FWIW my old '92 LWB 2WD S-10 with 4.3 TBI, 700R4 and 3.08's got 26 MPG average and I drove it like I stole it. Should have never sold it.
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Old 03-16-2011, 05:23 PM
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X 2 with hippie. Those are very prone to leaking.
Do yourself a favor. Pull the spark plugs and keep them in order. Chances are the 2 rear ones on the drivers side will be black. If they are there is a good possibiltiy(quite likely) that the fuel lines under the intake are leaking or the "spider is leaking fuel.
The 4.3 run pretty good, lots of pep. leave it alone. It is fine where its at.
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Old 03-16-2011, 06:17 PM
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Quote:
Originally Posted by 383SBC
Hey guys. So my girlfriend just bought a really nice, excellent condition 1994 chevy S10 SS 4.3 liter vortec V6.



So the truck runs nice and has great power, but.......... the fuel economy is the absolute worst on ANY engine I have ever seen! My friends supercharged 502 big block gets better mileage than this 4.3 vortec!! I don't even think it is getting 5 km to the liter right now. The truck only has 190,000km on it, very low for a '94! So the previous owner installed a dual flowmaster exhaust, a K&N intake, and an upgraded "chip". Correct me if I am wrong but the only one of these I could see affecting fuel mileage would be the computer chip. I have heard these engines are terrible on fuel but I could have never imagined it would be this bad! Hard to believe a small or big block V8 makes MORE power and burns LESS fuel, imagine that! So is this just how these engines are? Is there any tricks you folks have used in the past to increase the fuel efficiency of these trucks? It is costing her $20 to go to work and back everyday right now. I`m even beginning to think that there may be a fuel leak or something because this is just wrong. Any tips or info you have is appreciated!

Keith
1995 could have the LB4 version with TBI or the L35 with the troublesome CPI injection. You need to take a look at the VIN code or remove the air cleaner. If what's under the air cleaner looks like a 2 barrel carburetor with a pair of electric injectors in high mounted pod it's TBI.

Either can be hot rodded which will reduce mileage but the CPI has additional technical problems the TBI doesn't. Fixing the CPI can get more expensive than it's worth.

Bogie
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Old 03-16-2011, 07:41 PM
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Migh t want to check into the rear gear. It might be a 3.73 or 4.10 to make up for the lack of power the engine made. Big Three famous for that. 4.3 is a workhorse but one of the most underpowered and noiseiest you'll ever hear. MPG was never a consideration with them.
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Old 03-17-2011, 11:21 AM
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After checking and replacing the spider do it a huge favor and install a new timing chain, that`s the other half of the problem.
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