Engine runs poorly, burns gas

SGORDON80

MEMBER
2003 GMC C2500
6.0L
V8
4WD
AUTOMATIC
100,000 MILES

Catalytic converters have been gutted before I got the truck not showing check engine light but getting fuel system lean bank 1 an bank 2. It burns gas bad 9.8 MPG was getting 11.5. Six months ago truck has been totaled before with rebuilt title, new coil packs, wires, plugs, and injectors. Cleaned mass air flow meter. Does it have to do with 02 sensors not reading properly? Would moving them change anything heat wise?

1 Reply

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi,

The idea that you have a lean mixture is usually the result of only a few things. The most common is an engine vacuum leak. The second is a weak fuel pump. And last, a faulty engine coolant temperature sensor can cause issues.

So, if you have a live data scan tool, when the engine is cold, check the ECT signal. The temperature listed should be very close to ambient temperature. If that checks good, let me know what the short-term fuel trims are.

If you don't have a live data scan tool, first check for an engine vacuum leak. Here is a link that explains how to check:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

If no leaks are found, check to see if the fuel pressure is within the manufacturer's specifications. Here is a link explaining how to test:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Let me know what you find, if you have other questions, or if you have other questions.

Take care,

Joe