Gas mileage TERRIBLE - Page 2 - F-Body Online

Phate · 02-05-2008, 11:56 AM

Quote:

Originally Posted by FBC Performance

An O2 sensor can get "lazy" which its slow to read from lean to rich. If this is the case its not always going to throw a code since for the most part the PCM is just looking for the voltage to cross over the .450mv threshold. So if its taking longer to make the transitions from lean to rich or vice versa the pcm is throwing extra fuel to make it get to the rich side. They don't really give the PCM a time frame for the switching to occur.

But still, a 'lazy' 02 sensor is still going to throw a code. I've built wideband O2 sim's for my car out of RadioShack parts before, and regardless if the sensor is functioning correctly, if its reading heavy in one direction at any point in time, its going to throw an EGR code for running too rich a mixture and not being able to burn off the extra, and clogging the EGR with carbon.

FBC Performance · 02-05-2008, 05:09 PM

Quote:

Originally Posted by Phate

But still, a 'lazy' 02 sensor is still going to throw a code. I've built wideband O2 sim's for my car out of RadioShack parts before, and regardless if the sensor is functioning correctly, if its reading heavy in one direction at any point in time, its going to throw an EGR code for running too rich a mixture and not being able to burn off the extra, and clogging the EGR with carbon.

Yes it will throw a code eventually. But they are pretty much flat lining at that point when it finally does. Would you be talking about the post cat O2 though?
This is from John, One of the techs

copekyle · 02-05-2008, 06:07 PM

OK.... So tell me exactly what to check here and how to do it... the only way I know how to check O2's is to change them... same with the fuel filter... I officially got about 12 miles to the gallon on this tank... so I know there's something wrong but the engine seems to be running completely normal.

Phate · 02-05-2008, 08:29 PM

Quote:

Originally Posted by FBC Performance

Yes it will throw a code eventually. But they are pretty much flat lining at that point when it finally does. Would you be talking about the post cat O2 though?
This is from John, One of the techs

Hey John, nice to meet ya. Im Jonathan, otherwise known as Phate. And yes I was talking about post cat O2.

But I honestly dont see what could cause that dramatic a drop in fuel mileage without a major issue. He should be getting about 24mpg pending he doesnt 'drive it like he stole it'. I honestly dont know what to tell you though. Unless you have a fuel pressure gauge sitting around to check your lines (and it could still be a possible injector issue), and even using a new(er) scan tool, you cant read fuel delivery or 02, because of the age of the car.

FBC Performance · 02-05-2008, 10:52 PM

Quote:

Originally Posted by Phate

Hey John, nice to meet ya. Im Jonathan, otherwise known as Phate. And yes I was talking about post cat O2.

But I honestly dont see what could cause that dramatic a drop in fuel mileage without a major issue. He should be getting about 24mpg pending he doesnt 'drive it like he stole it'. I honestly dont know what to tell you though. Unless you have a fuel pressure gauge sitting around to check your lines (and it could still be a possible injector issue), and even using a new(er) scan tool, you cant read fuel delivery or 02, because of the age of the car.

It sounds like he might want to get the car tuned or at least checked out on a dyno, what do you think? This is FBC-Performance

copekyle · 02-06-2008, 12:56 AM

Alright... I have no problem getting it tuned up... I live in a small town and I don't know of any shop that has a dyno. I just kind of want an idea of what I'm looking at so I don't get ripped off at the shop. There's no many reputable shops here and if you don't know your stuff... they'll take you for a ride! If you guys have any other ideas... hit me with them. I actually have no post cat O2 sensor and I am using a simulator purchased through after thoughts auto. YA for no emission regulation in IDAHO!!!!

Thanks Guys

Kyle

FBC Performance · 02-06-2008, 12:47 PM

Quote:

Originally Posted by copekyle

Alright... I have no problem getting it tuned up... I live in a small town and I don't know of any shop that has a dyno. I just kind of want an idea of what I'm looking at so I don't get ripped off at the shop. There's no many reputable shops here and if you don't know your stuff... they'll take you for a ride! If you guys have any other ideas... hit me with them. I actually have no post cat O2 sensor and I am using a simulator purchased through after thoughts auto. YA for no emission regulation in IDAHO!!!!

Thanks Guys

Kyle

We just changed our pricing from 550 to 750 for tuning. We found we were as much as $400 off of nearby shops on tuning.

Phate · 02-06-2008, 02:07 PM

Geez. I dont realize how expensive that stuff really is sometimes since I know so many people in the industry..