poor gas mileage?
Thread Starter
Melting Slicks
Joined: Apr 2008
Posts: 2,118
Likes: 2
From: Redding CA
poor gas mileage?
hey guys i used to get 30-32 mpg. I just took a 4 hour trip and i was getting 24 mpg with ac off and about 20 mpg with AC on. this was at 70 mph. what could have made my mpg drop so drastically?
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
- Lazy or dead O2 sensors
- Dirty MAF sensors. (clean with MAF cleaner)
- Vacuum Leak
- Clogged CATs (effects WOT Power also)
- Clogged/dirty Airfilter (loss of power also)
Data Log your engine and see what the LTFT and O2 sensors are doing.
BC
- Dirty MAF sensors. (clean with MAF cleaner)
- Vacuum Leak
- Clogged CATs (effects WOT Power also)
- Clogged/dirty Airfilter (loss of power also)
Data Log your engine and see what the LTFT and O2 sensors are doing.
BC
Thread Starter
Melting Slicks
Joined: Apr 2008
Posts: 2,118
Likes: 2
From: Redding CA
ok so far i have cleaned my MAF and cleaned my Blackwing intake. can i clean my o2 sensors or would i have to just replace? i looked for vacuum leaks but havent found any. i dont have any codes. how would i find out if my cats are clogged?
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
You should have someone datalog your car. There are several ways you cn do that.
Use EFI Live, HP Tuners or purchase a aftermarket scanner that has real time data view and it will display O2 sensor output. I have a ACTRON CP9180 for my 08 Jeep and it will read any OBDII or CAN Buss PCM /ECM.
Data logging doesnt need a licsense so if you find someone with EFI Live or HP Tuners to do it, it normaly wont cost you anything. Well, maybe a beer or two.
My scanner was only $130. and well worth the cash. Its a very useful tool. I also have EFI Live for my C5 and C6
You cant not really clean an O2 sensor. Once they wear out, stick a fork in it,,,,Its DONE!
If it is not switching properly, thats your issue.
My son purchased a used Pontiac Grand AM yesterday. He had a LEAN BANK 1 DTC after he hammered it. The ACTRON Scanner showed bank 1 O2 sensor hanging out at .450 mv. The other O2 sensor was cycling properly 150-850 mv.
Bill
Use EFI Live, HP Tuners or purchase a aftermarket scanner that has real time data view and it will display O2 sensor output. I have a ACTRON CP9180 for my 08 Jeep and it will read any OBDII or CAN Buss PCM /ECM.
Data logging doesnt need a licsense so if you find someone with EFI Live or HP Tuners to do it, it normaly wont cost you anything. Well, maybe a beer or two.
My scanner was only $130. and well worth the cash. Its a very useful tool. I also have EFI Live for my C5 and C6
You cant not really clean an O2 sensor. Once they wear out, stick a fork in it,,,,Its DONE!
If it is not switching properly, thats your issue.My son purchased a used Pontiac Grand AM yesterday. He had a LEAN BANK 1 DTC after he hammered it. The ACTRON Scanner showed bank 1 O2 sensor hanging out at .450 mv. The other O2 sensor was cycling properly 150-850 mv.
Bill
Thread Starter
Melting Slicks
Joined: Apr 2008
Posts: 2,118
Likes: 2
From: Redding CA
You should have someone datalog your car. There are several ways you cn do that.
Use EFI Live, HP Tuners or purchase a aftermarket scanner that has real time data view and it will display O2 sensor output. I have a ACTRON CP9180 for my 08 Jeep and it will read any OBDII or CAN Buss PCM /ECM.
Data logging doesnt need a licsense so if you find someone with EFI Live or HP Tuners to do it, it normaly wont cost you anything. Well, maybe a beer or two.
My scanner was only $130. and well worth the cash. Its a very useful tool. I also have EFI Live for my C5 and C6
You cant not really clean an O2 sensor. Once they wear out, stick a fork in it,,,,Its DONE! If it is not switching properly, thats your issue.
My son purchased a used Pontiac Grand AM yesterday. He had a LEAN BANK 1 DTC after he hammered it. The ACTRON Scanner showed bank 1 O2 sensor hanging out at .450 mv. The other O2 sensor was cycling properly 150-850 mv.
Bill
Use EFI Live, HP Tuners or purchase a aftermarket scanner that has real time data view and it will display O2 sensor output. I have a ACTRON CP9180 for my 08 Jeep and it will read any OBDII or CAN Buss PCM /ECM.
Data logging doesnt need a licsense so if you find someone with EFI Live or HP Tuners to do it, it normaly wont cost you anything. Well, maybe a beer or two.
My scanner was only $130. and well worth the cash. Its a very useful tool. I also have EFI Live for my C5 and C6
You cant not really clean an O2 sensor. Once they wear out, stick a fork in it,,,,Its DONE!
If it is not switching properly, thats your issue.My son purchased a used Pontiac Grand AM yesterday. He had a LEAN BANK 1 DTC after he hammered it. The ACTRON Scanner showed bank 1 O2 sensor hanging out at .450 mv. The other O2 sensor was cycling properly 150-850 mv.
Bill
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Le Mans Master
Joined: Oct 2005
Posts: 7,088
Likes: 1,829
From: Metro Detroit Michigan
Bill, how will a dirty air filter cause a loss of fuel economy in MAF sensor controlled engine? The filter would reduce air flow, but I'd think that the MAF would sense the change in air flow, and reduce fuel accordingly.
Le Mans Master
Joined: Jun 2009
Posts: 6,528
Likes: 752
From: South Dakota
Is there something we are missing?
Thread Starter
Melting Slicks
Joined: Apr 2008
Posts: 2,118
Likes: 2
From: Redding CA
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
I drive my car in the winter (when theres no snow) and the filter got damp and froze. Traction in the cold sucks so I wasn't testing WOT. The car had a fresh fill up and the average fuel mileage meter was recently set to zero.
Normally around town mileage in my 98 coupe was 15-17. I wasn't able to get more than 12-13 and throttle response was not as crisp. It was 20 degrees out so I thought it due to the cold but it had never performed like that in the past when it was cold out.
I opened the hood and noticed that the accordion tube between the plastic duct and the TB was sucked in and thats when I checked the filter. It had ICE on it and it was frozen solid.
Thats what happens when you cut open the air box for more air and don't have a hood seal and it rains a couple days before.
You can relate that to a very dirty air filter.
Normally around town mileage in my 98 coupe was 15-17. I wasn't able to get more than 12-13 and throttle response was not as crisp. It was 20 degrees out so I thought it due to the cold but it had never performed like that in the past when it was cold out.
I opened the hood and noticed that the accordion tube between the plastic duct and the TB was sucked in and thats when I checked the filter. It had ICE on it and it was frozen solid.
Thats what happens when you cut open the air box for more air and don't have a hood seal and it rains a couple days before.
You can relate that to a very dirty air filter.
Burning Brakes
Joined: Oct 2007
Posts: 1,093
Likes: 33
From: Morristown TN
I noticed a 5MPG drop all of a sudden a few weeks ago.
I also noticed the slight smell of oil.
the 1st thing I checked was the PCV valve hoses and found mine broken where the Valve connects and goes from a large hose to a small one.
I could not find a direct replacement so I jerry rigged one up with fuel line and hose reducers.
My gas mileage picked back up and maybe a bit better.
I averaged just over 30mpg from Tennessee to Daytona.
Plus while I am here in Daytona in stop and go traffic and sitting in the car with the ac on while the wife goes in small shops I am still averaging 23mpg.
I also noticed the slight smell of oil.
the 1st thing I checked was the PCV valve hoses and found mine broken where the Valve connects and goes from a large hose to a small one.
I could not find a direct replacement so I jerry rigged one up with fuel line and hose reducers.
My gas mileage picked back up and maybe a bit better.
I averaged just over 30mpg from Tennessee to Daytona.
Plus while I am here in Daytona in stop and go traffic and sitting in the car with the ac on while the wife goes in small shops I am still averaging 23mpg.
