# chevy 4.3 MPG problem



## k1500 (Jan 14, 2008)

I have a 1994 chevy 1500 with a 4.3 vortec and my fuel mileage went down to about 10 miles per gallon. i replaced the plugs and that doesnt help. I noticed if i am in a drive thru or let the truck idle for a little bit the check engine light comes on but if i shut it off and start it back up it isnt on. Does anyone have any idea whats goin on with my truck?


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## RIGHTE0US (Jan 7, 2008)

Have a diagnostics test run on the system. It would be a pointless venture to play guessing games with this. By the way, when you put new spark plugs in, I would have suggested gapping them about 5 degrees more than specified...longer spark for cold start and better mpg after warm up. That's a little trick I learned back some years ago after many complaints about mpg dropping after changing the plugs.


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## qldit (Mar 26, 2007)

Good Afternoon k1500, lousy fuel consumption can also be associated with poor exhaust flow or poor engine inlet air flow.

You might check your air ducting and air filter, I have no suggestion for checking the exhaust system apart from disconnecting it, someone may have an idea along that line.

I have struck exhausts that were restricted, but usually you can tell by the sound and observing the exhaust flow at the tailpipe. 
The muffler or other components can become blocked or crushed.

This could also give an odd engine light because of odd engine parameter operation.

Others will have different ideas.

Cheers, qldit.


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## speedster123 (Oct 18, 2006)

you need to have the code read on the check engine light. go to autozone, they will do it for free. some components on the emissions, such as one solinoid valve comes on at 130 degrees, its the return system to re-burn gas tank vapors.
if its the infamous po446 code, this could be anything from the engine to the gas tank.
on my 4.3, we had to do a smoke test, found 2 leaks in the lines [vapor lines back to motor] .. replaced 2 solonoid valves in line [waste of money]..a few vacuum leaks..and.was about to replace the $160 charcoal cannister when someone mentioned the pressure sensor mounted on top of the gas tank. [which doesnt even show on a printout from chevy] dropped the tank and replaced it, cleared the code...it never came back on.


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## 1 g0t 0wn3d (Jan 31, 2007)

whens the last time you cleaned or replaced the fuel filter


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## bruiser (Jul 30, 2005)

Yes, get the code pulled. O2 sensors are another source of poor mileage.


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