HORRIBLE mpg.....why?

[GNguy]

Hey guys,
well I have been keeping track of my mpg lately and they are low....like 10-12mpg!! Even when I drive like grandma, I get like 175-200 miles a with like 12-13 gallons in it. I have 009 injectors with a Jim Testa chip(this is what I was told by the original owner, hboost, but he is now refusing to answer any calls) but anyways I got some msd 50s and a 8 position chip for them to start fresh, maybe this will help, I dont know. Should I get a different chip for the 50s maybe? I dont know anymore....any help would be great. thanks

 

[scottyb]

Make sure you have the correct 3.42 gear and you're getting converter lockup.

 

[XLR8]

If your O2 sensor is not functioning properly your MPG will suffer.

 

[2QUIK6]

Originally posted by GNguy
I got some msd 50s and a 8 position chip for them to start fresh, maybe this will help, I dont know. Should I get a different chip for the 50s maybe?

If you put the 50's in and do not get a chip specifically for them, your mpg will get even worse and may not run very well.

As for your current problem, a bad O2 will do it. Do you have a scan tool?? If not, you need to get one and find out what your BLMs are and O2 cross-cnts. O2 should cycle cross-counts from 0-255 in less than 90 secs, if not change it. Is it a AC Delco O2? If not, change it...shoudl have a purple wire on it...if its black its probably a Bosch..which is crap and probably the cause of your problem.

 

[GNguy]

I have Poston/Caspers heated 02 sensor and I run race gas every so often and sometimes the 02 counts just drop to like 97 from like 750 WHEN idling.....does that mean bad 02 sensor? I am pretty sure they are the 3.42 gears....how would I find out if they werent?

 

[2QUIK6]

Originally posted by GNguy
I have Poston/Caspers heated 02 sensor and I run race gas every so often and sometimes the 02 counts just drop to like 97 from like 750 WHEN idling.....does that mean bad 02 sensor?

Its the cross-counts you want to look at, not the O2 mv reading. Yes at idle the O2 mv will be all over the place as it just takes an average.
As far as gearing, if you are turning around 2k rpms at a 60mph cruise in 4th gear, then you have the stock gears. If more rpms than that, then your convertor may not be locking...simple test is at your 60mph cruise, keep your foot on the gas and tap the brake with your other foot, the rpms should jump up a bit when you apply the brake with the other foot still steady on the gas.

 

[Quick6'n'-K.C.]

Do you have a aftermarket boost gauge with vacuum, if so do what are your vacuum readings?

My car blew the vacuum hose off the charcoal cannister this winter, long story short it was getting horrible gas mileage and my vac was only down to 11 or 12.... i thought the headgasket was finally out.
Now the hoses are fixed my vac is back up to 15 inches at idle, shoots to 20 when you completely let off the gas on the highway.
my MPG increased to 20MPG, thats 4 more MPG!!!
I also need to fix a header leak that just split last week, im sure that doesnt help my MPG either!

175 miles / by 12 gallons is 14.5 MPG
200 / 13 15.3

Factor in your tire size.... what size are they?

My car has 275/60/15s on my daily driver, that makes the MILEAGE read 7% lower than actual. So, if you ad 7 miles per 100 miles thats usually 14-18 more miles per tank full that you are not factoring in.
Use this thread to factor your percentage of missed mileage.
stock tire was 215/65/15

http://www.turbobuick.com/forums/showthread.php?s=&threadid=107870&highlight=tire+calculator

I use the bosch 02 sensors in all my cars, no problems here.


Have a quality weekend
BW

 

[TurboJim]

Originally posted by 2QUIK6
Its the cross-counts you want to look at, not the O2 mv reading. Yes at idle the O2 mv will be all over the place as it just takes an average.

Huh? What takes an average? You should see integrator move the opposite way as the O2. IOW, O2 falls to 300mV int should go up, O2's 700, int goes down. This is because the ECM is trying to control mixture and constantly over compensates (keeping it laymens terms) to build up/store oxygen in the cat for the cleaning process.

I never really concentrated on getting BLM's perfect, cuz it seemed no 2 cars liked the same thing and came up with BLM ranges I found acceptable in some injectors. For 009's my chips BLM's usually wound up in the 11x's. If your idle BLM has learned over 128 for 009's then I'd look into an O2 sensor dying, or another reaon the ECM things the car is lean.

Does your lockup work? That will have a decent effect on mileage. Back in the day, my chips usually got over 20mpg and some as high as 28 on the highway. Not as good as Bruce, but not too shabby for a jerkoff out of Joisy

 

[2QUIK6]

Originally posted by TurboJim
Huh? What takes an average? You should see integrator move the opposite way as the O2. IOW, O2 falls to 300mV int should go up, O2's 700, int goes down.

The INT does not change instantaneously with the O2 reading. The O2 bounces up and down, with very cross-count, the high and the low reading are essentially averaged. Cross-count means the O2 has crossed from above stoich to below stoich...the average between the peak and valley should be stoich, otherwise fuel is added or removed. That's basically in laymens terms how the O2 functions.

 

[GNguy]

thanks for all the help guys, I think I am just gonna replace the o2 sensor and get a new lockup because I wanted to upgrade anyways....this just gives me a reason. any other ideas? thanks for the help guys.

 

[LaBuick]

definatly replace the TC lockup solenoid and maybe replace the converter, and if you haven't done it by now, I would remove the cats with straight pipe too.
I've gained 2 xtra mpg by removing the monolithic cats and dropped my temp by 6 deg.

 

[GNguy]

I dont have cats on the car, but I will replace that TC solenoid, thanks for reminding me. I have 3 inch exhaust all the way back.

 

[TurboJim]

Originally posted by 2QUIK6
The INT does not change instantaneously with the O2 reading. The O2 bounces up and down, with very cross-count, the high and the low reading are essentially averaged. Cross-count means the O2 has crossed from above stoich to below stoich...the average between the peak and valley should be stoich, otherwise fuel is added or removed. That's basically in laymens terms how the O2 functions.

Actually yes it does. Soon as O2 hits 300mV or 600mV (going by memory, I can look it up if you want. I used to change these values on emissions chips to change the target AF ratio.. and yes there is a few mS delay before int changes...which you can change in the chip) integrator will move to reflect its fueling changes. Crosscount means it passed bias voltage from technically lean to technically rich. (above and below 445 mV)

There is no average taken and if you were to watch mixture on a wideband it wouldnt sit at 14.8, it would be going 13.x-15.x and bouncing around there and in between. I guess if you averaged all the ratio's sampled in a set time, you;d average close to or at stioch...if thats what you meant..then you're right.

IN any event, no crosscounts means there is somethign wrong. If the ECM is in control, you SHOULD see crosscounts. The counter counts up to 255 then starts over. Thats why you might see 20 in one frame, then 2 in another frame etc. If you watch on an ALDL based scan tool you might see the 20 counts, then 2 counts etc. If you watch it on direct scan, you can actualy watch crosscounts count up. A slow or non counting counter might mean the O2 is lazy or dead which will definately affect mileage.

The fact you have or dont have a cat does not change the ECM's strategy. It will work as if you had a cat unless you have someone like Eric make you an open loop type chip, but if you're gonna do that, you might as well throw a carb on it!

 

[2QUIK6]

Originally posted by TurboJim
There is no average taken and if you were to watch mixture on a wideband it wouldnt sit at 14.8, it would be going 13.x-15.x and bouncing around there and in between. I guess if you averaged all the ratio's sampled in a set time, you;d average close to or at stioch...if thats what you meant..then you're right.

Yeah I wasn't clear on that, meant averaged by the ECM in order to determine INT/BLM.
If running lean, the INT will increase fairly rapidly until reaching a certain point, then the BLM will increase by 1, and the INT will start over at 128...if it continues to increase, then BLM increases by 1 again and INT starts over at 128 and so on until INT stabilizes.
Less or more fuel over what is programmed is determined by the BLM and INT, BLM is a larger multiplier to the base fuel than the smaller ratio'd INT value.

 

[VadersV6]

I fought with this issue from day 1, and it never got much better no matter what I did. I only went from 8mpg to 15 after all the things I did with the car. The car had 4.56's in it when I bought it (I was told they were 4.11's), but changing the gears didnt amount to any improvement in mileage. Only thing left is my torque converter The guy I bought it from didnt know what was in it, and I couldnt get the original owner to call me. (so frustrating when you dont know what you have!) I found out what a non lock converter looks like, and found I have a non lock, and the thing doesnt even start to build boost till 3000-3200, so its probabaly a 3800/4000 stall. I climb through mountains on the way to work, so combined with that stall, and I have a recipe for horrible mileage.
The Bosch o2's have a bad rep cause they dont last with lead, or maybe they fail early cause people bang them around and mishandle them when installing them. O2 sensors are fragile and should be treated that way, or they will fail fast. This was the case on older cars of mine. My idle O2 crosscounts used to only jump up 1-2 counts per frame, but seemed ok at cruise. This was a delco unit. After putting a Bosch one on, the idle cc's went up to about 20-30 counts per frame and 60-70 at cruise. That's an active sensor!
What are your idle and cruise BLM's? Mine used to be pegged at 90 until I dropped my BLM parameter down. I even had to create some intentional filtered leaks after my MAF to get my idle BLM's in an acceptable range.
1st thing to always check, is vacuum leaks and ignition problems. Then check for lockup of the torque converter. Read around on here and youll find out how to make a switch to force it to come on. The switch didnt work for me, so it forced me to look elsewhere, and thats when I found I had a converter that was crap for street use. I think the guy who put my car together had mental problems or a crack habit. 4000 stall and 4.56's ( in a 7.5" rear end no less) on a GN with a stock fuel pump and exhaust, with a bigger turbo and ported heads/cam. Awesome combo there!

 

[MaxVO2]

Originally posted by VadersV6 and thats when I found I had a converter that was crap for street use. I think the guy who put my car together had mental problems or a crack habit. 4000 stall and 4.56's ( in a 7.5" rear end no less) on a GN with a stock fuel pump and exhaust, with a bigger turbo and ported heads/cam. Awesome combo there! [/B]

****That's hysterical. I think I might have known that guy who originally owned your car. If it's the same guy, he used to be on several auto boards a few years back, and was absolutely convinced 4.56's and super high stall was THE combo for our cars. Something about it getting out of the hole faster, staying in it's torque curve longer, and using all 4 gears, and less drag from the 7.5 rear due to less mass, blah blah. You couldn't tell him anything, he had it all figured out, and had the high 13 second time slips to prove it!

Glad the car found a better home!

Billy

 

[turbo2nr]

that's funny!

 

[VadersV6]

Originally posted by MaxVO2
****That's hysterical. I think I might have known that guy who originally owned your car. If it's the same guy, he used to be on several auto boards a few years back, and was absolutely convinced 4.56's and super high stall was THE combo for our cars. Something about it getting out of the hole faster, staying in it's torque curve longer, and using all 4 gears, and less drag from the 7.5 rear due to less mass, blah blah. You couldn't tell him anything, he had it all figured out, and had the high 13 second time slips to prove it!

Glad the car found a better home!

Billy

Wow. Any recollection of what his user name was? I know his real name, and I have his parents phone number (he's 35 and living with his parents), but he wouldnt return the call.
I'm scared of what else this guy may have done to the car when he had it. It would be cool to find his user name and check out his mod list. Remember if he was from SoCal?
The guy I bought it from was told that the engine had been recently rebuilt and had 4000 miles on it. LMAO. The engine has no sign of new paint (down to raw iron), and everything else looks old as hell.

 

[GNguy]

vader, did you happen to buy it from a guy in southgate? Because the guy I bought it from has had numerous TRs, so maybe it might be the same guy.

 

[VadersV6]

He was an asian guy named kenneth