Great Lakes 4x4. The largest offroad forum in the Midwest banner

1 - 16 of 16 Posts

·
Registered
Joined
·
10 Posts
Discussion Starter · #1 ·
i own a 2004 chevy Z71 w/ 285 75 17 BFG TA KO tires. Everything else is stock. I have had the tires about a year and a half. About 6 months ago my gas mileage went from 17 mpg to 13 real quick. I have checked and changed everything simple such as fuel, oil, plugs and wires, air filter. My tires are running 50 psi. I take off slow and drive about 65 on the highway. is it my or my truck? and helpppp.
 

·
Registered
Joined
·
495 Posts
How many miles? Probably due for O2 sensors and EGR valave. When those go bad, the computer thinks you are polluting and adds fuel to cool the spark. Are you loseing power in the hills too?
 

·
Registered
Joined
·
10 Posts
Discussion Starter · #4 ·
Its got 47000 miles. If and O2 sensor is bad will it always pull a check engine light? Also, the temp here right now is about 95-100 F. After driving for little while with the AC running full blast when I come to a stop light it stops blowing cold air. It also feels like I am losing power in the hills.
 

·
Registered
Joined
·
495 Posts
Suppose to put out a code, but whos to say it works? Mine only put out 1 code for one o2 sensor, didn't throw codes for the other 3. Also didn't throw a code for the egr.
 

·
Registered
Joined
·
10 Posts
Discussion Starter · #11 ·
If an O2 sensor is bad and the comp adds or reduces fuel to adjust will it cause fouled spark plugs. If that is the case should start w/ the EGR? I pulled the plugs already and they were very clean.
 

·
The guy Dale doesn't know
Joined
·
4,182 Posts
i will get different mileage based on what kind of fuel i use. beyond that are you losing any coolant? the reason i ask is that the intake gaskets are almost a common problem in the ls motors. also the ecm will store dtc's and not trip the check engine light. you said you checked the common stuff. did you replace the spark plugs?

the ecm in those pickup learns your driving style and adjusts to it. you can clear the memory from it by unplugging the battery and then turning on the lights. it may or may not make a difference.

btw i thought those trucks were coil on plug?
 

·
Registered
Joined
·
10 Posts
Discussion Starter · #13 ·
same here on the fuel, i get better mpg w/ shell v-power. no coolant loss, I pulled a few plugs and they were in good shape hardly any fouling. But, the engine has a missfire. I will try to reset the ecm and see if that helps. If not what about plug wires?
 

·
The guy Dale doesn't know
Joined
·
4,182 Posts
replace your plugs. make sure you get platinums.

i think the wires are attached to the coils, as in not replaceable. but i am not sure.

also if you are concerned about fuel mileage get a throttle body spacer and a k&n air filter. get the td performance spacer, it's cheap and it doesnt whistle. i used to sell them to my customers that were looking to get a couple extra miles to the gallon. it worked very well. should cost you about 75 bucks for both of them.
 

·
Registered
Joined
·
10 Posts
Discussion Starter · #16 ·
thanks for the help, i will do that and post the outcome. if there are anymore suggestions or points of interest that i need to look at im all ears.
 
1 - 16 of 16 Posts
Top