Horrible Gas Mileage
09-08-2005, 11:18 PM
#1
Launching!
Thread Starter
iTrader: (2)
Join Date: Feb 2004
Location: Ca.
Posts: 245
Likes: 0
Received 0 Likes
on
0 Posts
Horrible Gas Mileage Ever since ive owned the car its hasnt gotten the best gas mileage. I know by doing the cam swap it wasnt going to help it out. But i dont think i should be getting this bad gas mileage with the little amount of mods i have.
I usually never fill up all the way. I always fill up to 3/4s of a tank running California 91 octane gas. Chevron, 76, and or shell... No matter how im driving weather its slow or fast im always half throttle or keeping the rpms under 3k i always manage to get about 60 - 80 miles outa the 3/4 tank of gas. Whats up with that? This is mostly city driving... And some freeway driving. Although im not doing too much stop and go in the city.
My car has about 38k miles. I've changed the fuel filter 2 times. Ran fuel injector cleaner. I have hp tuner and the ive even tryed making the car run leaner, but thats didnt help out anything neither. So what can it be?
Mods in my sig
I usually never fill up all the way. I always fill up to 3/4s of a tank running California 91 octane gas. Chevron, 76, and or shell... No matter how im driving weather its slow or fast im always half throttle or keeping the rpms under 3k i always manage to get about 60 - 80 miles outa the 3/4 tank of gas. Whats up with that? This is mostly city driving... And some freeway driving. Although im not doing too much stop and go in the city.
My car has about 38k miles. I've changed the fuel filter 2 times. Ran fuel injector cleaner. I have hp tuner and the ive even tryed making the car run leaner, but thats didnt help out anything neither. So what can it be?
Mods in my sig
Last edited by Camaroguy; 09-08-2005 at 11:33 PM.
09-09-2005, 12:24 AM
#3
TECH Senior Member
also... what codes are you setting? (that poor of mileage i'm sure your SES light is on)
I get 12-14mpg in my 382, 236/242 cam, 4400 stall, no lockup , heavy foot car .. so something's definetly fubarred w/your car
we need to know:
when did this start?
what PCM tuning has been done? (if any)
what codes are set (SES) ?
I get 12-14mpg in my 382, 236/242 cam, 4400 stall, no lockup , heavy foot car .. so something's definetly fubarred w/your car
we need to know:
when did this start?
what PCM tuning has been done? (if any)
what codes are set (SES) ?
09-09-2005, 12:35 AM
#4
Launching!
Thread Starter
iTrader: (2)
Join Date: Feb 2004
Location: Ca.
Posts: 245
Likes: 0
Received 0 Likes
on
0 Posts
I really dont have any SES codes. The only ones i get is P0300 which is because im running NGK TR6's for nitrous use. Im gonna go ahead and change those to NGK TR 55s since im gonna shy off nitrous for awhile while i get my car back in shape along with new injectors.
Open or Closed loop? I know the difference but not sure which is which. So i believe im running in open loop which is where the computer responds to all the codes and adjusts whats needed to be adjusted. Closed is the opposite. Correct? Where everything is pretty much bypassed and the computer only does what the tune has in store.
This all started a long ago. Nothing new. I hardly have any mods, but its starting to be very annoying and expensive going to the gas station every day sometimes twice a day. The TR224 cam didnt change the mileage much if anything at all. Its had bad gas mileage problems before the cam just alittle worst now after the cam.
Tunning wise. The car is pretty stronge. Getting about 28* @ WOT. Stock Fuel Tables. The MAF was edited according to the VE table. AFR is about 12.6 with almost all 0's in ltft also with 28* timing @ WOT. I tryed to lean it out and run 13.0 AFR got around 6 - 12 on ltft again running 28* timing and still get the same damn gas mileage.
Open or Closed loop? I know the difference but not sure which is which. So i believe im running in open loop which is where the computer responds to all the codes and adjusts whats needed to be adjusted. Closed is the opposite. Correct? Where everything is pretty much bypassed and the computer only does what the tune has in store.
This all started a long ago. Nothing new. I hardly have any mods, but its starting to be very annoying and expensive going to the gas station every day sometimes twice a day. The TR224 cam didnt change the mileage much if anything at all. Its had bad gas mileage problems before the cam just alittle worst now after the cam.
Tunning wise. The car is pretty stronge. Getting about 28* @ WOT. Stock Fuel Tables. The MAF was edited according to the VE table. AFR is about 12.6 with almost all 0's in ltft also with 28* timing @ WOT. I tryed to lean it out and run 13.0 AFR got around 6 - 12 on ltft again running 28* timing and still get the same damn gas mileage.
09-09-2005, 12:45 AM
#5
Originally Posted by Camaroguy
Open or Closed loop? I know the difference but not sure which is which. So i believe im running in open loop which is where the computer responds to all the codes and adjusts whats needed to be adjusted. Closed is the opposite. Correct? Where everything is pretty much bypassed and the computer only does what the tune has in store.
I am going to say it maybe related to oxygen sensors. Do you ahve a log to see if they are switching properly? Are the O2 Codes on or off in the tune?
09-09-2005, 01:46 AM
#7
Launching!
Thread Starter
iTrader: (2)
Join Date: Feb 2004
Location: Ca.
Posts: 245
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Black02SS
No, its the opposite. Closed uses the oxygen sensors to help compensate for differences where open bypasses them and relies soley on the VE Table, Open Loop AFR table, and MAF Table (if not in SD)
I am going to say it maybe related to oxygen sensors. Do you ahve a log to see if they are switching properly? Are the O2 Codes on or off in the tune?
I am going to say it maybe related to oxygen sensors. Do you ahve a log to see if they are switching properly? Are the O2 Codes on or off in the tune?
Although i do have the rear o2 sensors deleted becasuse those are bad.
Trending Topics
09-09-2005, 02:29 AM
#8
i have been in open loop and mafless for 6 months and i have the same cam along with a lot more and i still get around 20mpg. p0300 doesnt seem like those plugs should do that. i think there is a bigger problem than plugs unless you have a bad one. did you change wires? good luck
09-09-2005, 12:47 PM
#11
Launching!
Thread Starter
iTrader: (2)
Join Date: Feb 2004
Location: Ca.
Posts: 245
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by redmist
What are your LTFTs? (Long term fuel trims)
Right now they are + 5... So the car is running lean.
Although that has really never made any difference in my gas milage..
Like i said, even before when the car had the stock cam and the stock tune. It never did good on gas. I might have seen 110 - 130 Miles on a FULL tank of gas. Mostly on the lower 110, 120 mile side. Again this is mostly city driving. But its not really stop and go. Pretty spaced out with max of 20 stop lights. (Of course im not stopping at all the lights) with speeds up to 40-70 mph. Car has stock 3.42 gears. I usually dont go past 3k. Im always shifting at 2.5k rpms, and cruzing at 1.9k - 2.3k
09-09-2005, 01:09 PM
#16
TECH Junkie
iTrader: (28)
Join Date: Jan 2004
Location: Houston
Posts: 3,250
Likes: 0
Received 0 Likes
on
0 Posts
The only other thing I could think of is your tune is off due to the dry shot. Something has to compensate for the fuel.
Have you tried flashing a stock tune back in to see if it makes a difference?
Have you tried flashing a stock tune back in to see if it makes a difference?
09-09-2005, 01:09 PM
#17
TECH Senior Member
when was the last time you changed the spark plugs?
At night open the hood w/the engine running, see if you can see any arching (broken wire... I had several break on me when it was really cold out... though being in california it's probably pretty rare to have sub zero degree days heh)
If the PCM is stock or near stock then that most likely isn't hte problem... let's look at this logically... as to what can contribute to poor fuel economy
1. Clogged fuel filter -- you've already changed
2. Clogged injectors -- You've run cleaner, and a clogged injector would be evident by a very rich condition on 1 bank..
3. Low tire pressure -- wouldn't cause to the degree you're having
4. Bad spark plugs -- Check them... if you have several bad spark plugs you're not getting a good burn.... you can check for misfires using your scan software
5. Bad O2 sensors -- if O2 sensors are bad it'll force you into open loop all the time which will result in **** poor gas mileage if you're not tuned for it ... should set an SES light
6. Bad MAF sensor -- should set a code
7. Clogged Cats -- would notice lack of power, but could also cause poor fuel economy... how old are the Magnaflow High Flow Cats?
8. Bad spark plug wires -- Not getting full combustion, if it's at the boot you'll see arching when it's dark out
That's all I could think of real quick... I would check the plugs and wires at this point ... even your pre cam fuel economy is way lower than it should be for an M6
Also that P0300 (misfire detected) has me thinking it's spark plug related (not just because you're running TR6s... I used to run TR6s years back before the cam and never got a P0300) ... so I'd start by checking the wires (I believe you can use an OHM meter for this) and spark plugs (make sure gap is correct and they don't show signs of out of the ordinary wear)
At night open the hood w/the engine running, see if you can see any arching (broken wire... I had several break on me when it was really cold out... though being in california it's probably pretty rare to have sub zero degree days heh)
If the PCM is stock or near stock then that most likely isn't hte problem... let's look at this logically... as to what can contribute to poor fuel economy
1. Clogged fuel filter -- you've already changed
2. Clogged injectors -- You've run cleaner, and a clogged injector would be evident by a very rich condition on 1 bank..
3. Low tire pressure -- wouldn't cause to the degree you're having
4. Bad spark plugs -- Check them... if you have several bad spark plugs you're not getting a good burn.... you can check for misfires using your scan software
5. Bad O2 sensors -- if O2 sensors are bad it'll force you into open loop all the time which will result in **** poor gas mileage if you're not tuned for it ... should set an SES light
6. Bad MAF sensor -- should set a code
7. Clogged Cats -- would notice lack of power, but could also cause poor fuel economy... how old are the Magnaflow High Flow Cats?
8. Bad spark plug wires -- Not getting full combustion, if it's at the boot you'll see arching when it's dark out
That's all I could think of real quick... I would check the plugs and wires at this point ... even your pre cam fuel economy is way lower than it should be for an M6
Also that P0300 (misfire detected) has me thinking it's spark plug related (not just because you're running TR6s... I used to run TR6s years back before the cam and never got a P0300) ... so I'd start by checking the wires (I believe you can use an OHM meter for this) and spark plugs (make sure gap is correct and they don't show signs of out of the ordinary wear)
09-09-2005, 03:15 PM
#18
TECH Regular
Join Date: Feb 2004
Posts: 438
Likes: 0
Received 0 Likes
on
0 Posts
Well if your LTFTs are postive and you are getting poor gas milage even before the mods then I would think it would be the O2 sensors. ie they are idicating a lean mixture when in fact it's rich. Have you had any emissions related problems at inspection time?
How is the perfromance of the car, does it kick *** or is it reluctant to wind out and generally unresponsive?
How is the perfromance of the car, does it kick *** or is it reluctant to wind out and generally unresponsive?
09-10-2005, 01:49 PM
#20
Launching!
Thread Starter
iTrader: (2)
Join Date: Feb 2004
Location: Ca.
Posts: 245
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by horist
when was the last time you changed the spark plugs?
At night open the hood w/the engine running, see if you can see any arching (broken wire... I had several break on me when it was really cold out... though being in california it's probably pretty rare to have sub zero degree days heh)
If the PCM is stock or near stock then that most likely isn't hte problem... let's look at this logically... as to what can contribute to poor fuel economy
1. Clogged fuel filter -- you've already changed
2. Clogged injectors -- You've run cleaner, and a clogged injector would be evident by a very rich condition on 1 bank..
3. Low tire pressure -- wouldn't cause to the degree you're having
4. Bad spark plugs -- Check them... if you have several bad spark plugs you're not getting a good burn.... you can check for misfires using your scan software
5. Bad O2 sensors -- if O2 sensors are bad it'll force you into open loop all the time which will result in **** poor gas mileage if you're not tuned for it ... should set an SES light
6. Bad MAF sensor -- should set a code
7. Clogged Cats -- would notice lack of power, but could also cause poor fuel economy... how old are the Magnaflow High Flow Cats?
8. Bad spark plug wires -- Not getting full combustion, if it's at the boot you'll see arching when it's dark out
That's all I could think of real quick... I would check the plugs and wires at this point ... even your pre cam fuel economy is way lower than it should be for an M6
Also that P0300 (misfire detected) has me thinking it's spark plug related (not just because you're running TR6s... I used to run TR6s years back before the cam and never got a P0300) ... so I'd start by checking the wires (I believe you can use an OHM meter for this) and spark plugs (make sure gap is correct and they don't show signs of out of the ordinary wear)
At night open the hood w/the engine running, see if you can see any arching (broken wire... I had several break on me when it was really cold out... though being in california it's probably pretty rare to have sub zero degree days heh)
If the PCM is stock or near stock then that most likely isn't hte problem... let's look at this logically... as to what can contribute to poor fuel economy
1. Clogged fuel filter -- you've already changed
2. Clogged injectors -- You've run cleaner, and a clogged injector would be evident by a very rich condition on 1 bank..
3. Low tire pressure -- wouldn't cause to the degree you're having
4. Bad spark plugs -- Check them... if you have several bad spark plugs you're not getting a good burn.... you can check for misfires using your scan software
5. Bad O2 sensors -- if O2 sensors are bad it'll force you into open loop all the time which will result in **** poor gas mileage if you're not tuned for it ... should set an SES light
6. Bad MAF sensor -- should set a code
7. Clogged Cats -- would notice lack of power, but could also cause poor fuel economy... how old are the Magnaflow High Flow Cats?
8. Bad spark plug wires -- Not getting full combustion, if it's at the boot you'll see arching when it's dark out
That's all I could think of real quick... I would check the plugs and wires at this point ... even your pre cam fuel economy is way lower than it should be for an M6
Also that P0300 (misfire detected) has me thinking it's spark plug related (not just because you're running TR6s... I used to run TR6s years back before the cam and never got a P0300) ... so I'd start by checking the wires (I believe you can use an OHM meter for this) and spark plugs (make sure gap is correct and they don't show signs of out of the ordinary wear)
Spark plugs i change every 8 - 10k miles. Since they are the TR6's they do foul out fairly fast.
I did have bad o2s on the passanger side bank 2 sensor 1 and bank 2 sensor 2. Due to an exhaust leak. So i disabled my two rear o2s and swapped my good o2 sensor from bank 1 sensor 2 in place of bank 2 sensor 1. And i put the bad one into Bank 1 sensor 2. And disabled both rear o2s. So i have two good o2 sensors in the front.
Clogged cats is a possibility. Although when i had the exhaust leak it was around the cats and i looked into the passanger side one and it looked very good. Ive had the new cats in there for almost 20k miles now.
Maf sensor. I have no codes.
I do have the stock spark plug wires. I havent noticed any kind of break in the wires. Although im not usually looking for that at night time. So ill have to pay attention to this next time.
Well if your LTFTs are postive and you are getting poor gas milage even before the mods then I would think it would be the O2 sensors. ie they are idicating a lean mixture when in fact it's rich. Have you had any emissions related problems at inspection time?
Never had any emissions related problems. The only problem i did have was when i got that exhaust leak it took out both my o2 sensors on the passanger side, and i fixed that.
The only other thing I could think of is your tune is off due to the dry shot. Something has to compensate for the fuel.
Although ive had a nitrous tune and a regulare N/A Tune before when my car had the stock cam. But the car has always had bad gas milage even before all the mods started.
stupid question, how many gallons of gas do you normally put in the car?