Gas Mileage
03-09-2010, 09:54 PM
#1
Gas Mileage I'm in need of some helo here guys. I have 99 Z28 and granted it has 209k on her she's still a strong runner but I'm getting extremely bad mileage, like 6mpg if I'm lucky and thats on premium or reg with grandma driving, lead foot just kills my wallet so its pointless.
The plugs are good,oil was changed 180miles ago and the air filter is clean. I did have a check engine light on and the low coolant light aswell but the coolant is full and shouldnt be throwing a code. I ran a scanner on it during auto yesterday and it said that my bank 1,sensor 1 O2 sensor was causing it to throw a code. Which I'm going to check it and see if maybe its just got carbon build up on it. It was also throwing 2 different codes for the throttle body, one for low amps and one for something about my MAF. Before I got the car my brother had changed the MAF appearently. The throttle mod wasn't done to the throttle stop. Also I have ran 3 bottles of STP Fuel treatment through my car since I got it 4months ago. I used it once a month, first was reg fuel treatment and another was high mileage treatment and the 3rd was some kinda special high mileage treatment.
Before my brother in law sold the car to my brother, he was driving it between wyoming and illinois so thats where most of the miles came from which he says he was getting waaaaayyyy better mileage then that. My buddies ol chevy with a suspension lift and 36in tires with a cammed,stroked350 is getting better mileage then I, pretty sad.
I would really appreciate the help here guys, this gas mileage is killing my thin highschool student wallet.
The plugs are good,oil was changed 180miles ago and the air filter is clean. I did have a check engine light on and the low coolant light aswell but the coolant is full and shouldnt be throwing a code. I ran a scanner on it during auto yesterday and it said that my bank 1,sensor 1 O2 sensor was causing it to throw a code. Which I'm going to check it and see if maybe its just got carbon build up on it. It was also throwing 2 different codes for the throttle body, one for low amps and one for something about my MAF. Before I got the car my brother had changed the MAF appearently. The throttle mod wasn't done to the throttle stop. Also I have ran 3 bottles of STP Fuel treatment through my car since I got it 4months ago. I used it once a month, first was reg fuel treatment and another was high mileage treatment and the 3rd was some kinda special high mileage treatment.
Before my brother in law sold the car to my brother, he was driving it between wyoming and illinois so thats where most of the miles came from which he says he was getting waaaaayyyy better mileage then that. My buddies ol chevy with a suspension lift and 36in tires with a cammed,stroked350 is getting better mileage then I, pretty sad.
I would really appreciate the help here guys, this gas mileage is killing my thin highschool student wallet.
03-09-2010, 10:10 PM
#2
200k +!
WELL, I would start were the codes are coming from.
What was change from the MAF?
At I would also replace the O2 sensor...
have you change the fuel filter?
STP TREATMENT wont clean your system.
Try some thing like Techron, Zmax,Restore, Prestone fuel system CLEANERS.
what weight of oil are you using? synthetic? semi?
dont tell me regular oil......
WELL, I would start were the codes are coming from.
What was change from the MAF?
At I would also replace the O2 sensor...
have you change the fuel filter?
STP TREATMENT wont clean your system.
Try some thing like Techron, Zmax,Restore, Prestone fuel system CLEANERS.
what weight of oil are you using? synthetic? semi?
dont tell me regular oil......
03-09-2010, 10:22 PM
#4
ws6-I dont remember the code for the MAF off hand, I'll see if I can run it again tommorow and I'll write the codes down. I'm running 5w30 synthetic oil, winters in wyoming aren't fun at -20f. I will look into the lister cleaners thanks. And I was going to change the fuel filter just havne't had the chance to go by napa or oreilly's and pick one up.
99formula- Theres no gas leaks or any leaks of any kind from what I've seen when working on the car. The headers were leaking but that was do to bad gaskets on the collectors, I replaced them shortly after getting the car.
I'll ask my brother what exactly what he did to the MAF, I'm pretty sure he just swapped out the hole unit but I'm not certain.
99formula- Theres no gas leaks or any leaks of any kind from what I've seen when working on the car. The headers were leaking but that was do to bad gaskets on the collectors, I replaced them shortly after getting the car.
I'll ask my brother what exactly what he did to the MAF, I'm pretty sure he just swapped out the hole unit but I'm not certain.
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03-10-2010, 08:19 AM
#8
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Bad O2 sensor will default the PCM to run real rich, that car is puking out unburnt gas....change the O2 and just replace the MAF with a stocker, you should be back up to 20+ with that.
Does the car have cats? They also may be clogged
Does the car have cats? They also may be clogged
03-10-2010, 08:23 AM
#9
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First off,
Tuneup(plugs, wires, fuel filter)
Clean Maf with maf cleaner
Clean TB with TB cleaner
Change your front o2 sensors.
Problem should be cured and back into the 20s mpg range
Tuneup(plugs, wires, fuel filter)
Clean Maf with maf cleaner
Clean TB with TB cleaner
Change your front o2 sensors.
Problem should be cured and back into the 20s mpg range
03-10-2010, 09:21 AM
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I agree with these guys.
-New O2 sensor (actually, at that mileage I'd just replace both bank's front sensors)
-Clean/replace MAF with an as-manufactured unit (meaning no porting or descreening, etc.)
-New fuel filter (you said the air filter was good, otherwise replace that too)
-Plugs & wires (are these new? You weren't clear on that, other than saying the plugs were "good")
-IMO, the best fuel system treatment is a product called Red Line SI-1. It's the only one I use now, and the only one I recommend. It's worked wonders for me on more than one car.
See how it does with all of that. I don't know what state you live in, but if you don't have a visual or sniff emissions inspection, I'd also ditch the cats. They may be slightly clogged, but even if not you'll pick up a bit of power and MPG by removing them.
-New O2 sensor (actually, at that mileage I'd just replace both bank's front sensors)
-Clean/replace MAF with an as-manufactured unit (meaning no porting or descreening, etc.)
-New fuel filter (you said the air filter was good, otherwise replace that too)
-Plugs & wires (are these new? You weren't clear on that, other than saying the plugs were "good")
-IMO, the best fuel system treatment is a product called Red Line SI-1. It's the only one I use now, and the only one I recommend. It's worked wonders for me on more than one car.
See how it does with all of that. I don't know what state you live in, but if you don't have a visual or sniff emissions inspection, I'd also ditch the cats. They may be slightly clogged, but even if not you'll pick up a bit of power and MPG by removing them.
03-10-2010, 09:46 AM
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I agree with these guys.
-New O2 sensor (actually, at that mileage I'd just replace both bank's front sensors)
-Clean/replace MAF with an as-manufactured unit (meaning no porting or descreening, etc.)
-New fuel filter (you said the air filter was good, otherwise replace that too)
-Plugs & wires (are these new? You weren't clear on that, other than saying the plugs were "good")
-IMO, the best fuel system treatment is a product called Red Line SI-1. It's the only one I use now, and the only one I recommend. It's worked wonders for me on more than one car.
See how it does with all of that. I don't know what state you live in, but if you don't have a visual or sniff emissions inspection, I'd also ditch the cats. They may be slightly clogged, but even if not you'll pick up a bit of power and MPG by removing them.
-New O2 sensor (actually, at that mileage I'd just replace both bank's front sensors)
-Clean/replace MAF with an as-manufactured unit (meaning no porting or descreening, etc.)
-New fuel filter (you said the air filter was good, otherwise replace that too)
-Plugs & wires (are these new? You weren't clear on that, other than saying the plugs were "good")
-IMO, the best fuel system treatment is a product called Red Line SI-1. It's the only one I use now, and the only one I recommend. It's worked wonders for me on more than one car.
See how it does with all of that. I don't know what state you live in, but if you don't have a visual or sniff emissions inspection, I'd also ditch the cats. They may be slightly clogged, but even if not you'll pick up a bit of power and MPG by removing them.
03-10-2010, 10:24 AM
#12
I agree with these guys.
-New O2 sensor (actually, at that mileage I'd just replace both bank's front sensors)
-Clean/replace MAF with an as-manufactured unit (meaning no porting or descreening, etc.)
-New fuel filter (you said the air filter was good, otherwise replace that too)
-Plugs & wires (are these new? You weren't clear on that, other than saying the plugs were "good")
-IMO, the best fuel system treatment is a product called Red Line SI-1. It's the only one I use now, and the only one I recommend. It's worked wonders for me on more than one car.
See how it does with all of that. I don't know what state you live in, but if you don't have a visual or sniff emissions inspection, I'd also ditch the cats. They may be slightly clogged, but even if not you'll pick up a bit of power and MPG by removing them.
-New O2 sensor (actually, at that mileage I'd just replace both bank's front sensors)
-Clean/replace MAF with an as-manufactured unit (meaning no porting or descreening, etc.)
-New fuel filter (you said the air filter was good, otherwise replace that too)
-Plugs & wires (are these new? You weren't clear on that, other than saying the plugs were "good")
-IMO, the best fuel system treatment is a product called Red Line SI-1. It's the only one I use now, and the only one I recommend. It's worked wonders for me on more than one car.
See how it does with all of that. I don't know what state you live in, but if you don't have a visual or sniff emissions inspection, I'd also ditch the cats. They may be slightly clogged, but even if not you'll pick up a bit of power and MPG by removing them.
03-10-2010, 11:02 AM
#13
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I guess the universal would be fine, my problem is more with MAFs that have been modified from the factory configuration with which they were calibrated. As long as you install the unit as-is, out of the box from GM, if they say it'll work it probably would be fine.
What's the deal with the adapter though? Is it a phsyical adapter to make the MAF fit, or a wiring harness adapter?
03-10-2010, 12:36 PM
#14
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I was not aware that the original had been dis'coed by GM. That must've happend in pretty recent years.
I guess the universal would be fine, my problem is more with MAFs that have been modified from the factory configuration with which they were calibrated. As long as you install the unit as-is, out of the box from GM, if they say it'll work it probably would be fine.
What's the deal with the adapter though? Is it a phsyical adapter to make the MAF fit, or a wiring harness adapter?
I guess the universal would be fine, my problem is more with MAFs that have been modified from the factory configuration with which they were calibrated. As long as you install the unit as-is, out of the box from GM, if they say it'll work it probably would be fine.
What's the deal with the adapter though? Is it a phsyical adapter to make the MAF fit, or a wiring harness adapter?
03-14-2010, 01:41 PM
#15
Found the issue with the O2 sensor.......THERE ISN'T ONE! My brother is a dumbass and messed up the front drivers side one so he just unplugged it and but a bolt in the hole 
Napa was out of them of course, so I'll have one sometime this week.
Napa was out of them of course, so I'll have one sometime this week. 
