Alright so just recently i got a new trip meter and i decided to check my mileage off a full tank. i knew it was pretty bad but not this bad.. i topped off the tank one night and drove around all week. when i needed to fill up again i noticed i barely got 150 miles to the tank... i assume its a 12 gallon tank. ive heard other people getting in the range of 300 miles to the tank. id be happy with even getting low or mid 200's. mostly everything on my motor is new with the exception of injectors i believe. i usually seafoam the car every 6 months or so to keep it all decently clean id guess you can say. new cat new muffler. had a top end rebuild done around august im going to say.
so with that being said what are some things i can look into to get more mpg. i already built a home made CAI thats actually cold air.. timing?? not sure what my mechanic put but i believe he advanced it for some reason. should i put it back to normal?? i believe its 12 degrees right??
Spark plugs? i run autolite platinums i think. i dont believe i gapped them right tho...
wires?? i got regular autozone or oreilly ones..
could swapping out some stuff like the pcv or other stuff?? i dont have any vacuum leaks if i remember corectly.

My driving is mainly between valleys so i go up and down a mountain. nothing too hardcore or steep. so i wouldnt expect to get 30 mpg like others..
any help would be great. thanks guys.-Aaron

 

the best plugs for these engines is the stock ac delco plugs period r43tsk or r42ts/r43ts

check the timing gap the plugs correctly, has the car been down on power latley?

first thing that comes to mind is the maf sensor

 

When was the last time a FULL tune-up was done?

Replace the O2S. The SeaFoam degunking probably gunked it up.

Get rid of the overpriced crap Bosch platinum plugs and get the right Delco R42TS plugs in there.

16.5 gallon tank, BTW. I was down to a 1/4 tank on the gauge and got at least another 4 gallons out when I finally pumped it dry into a bucket so I could yank it out of the car. And I already know that it takes 12 gallons from 1/4 to full.

 

well i replaced everything in the car last year and im going to say then. i had the motor torn down and rehauled...
ok ill get the plugs... as far as i can tell power is great.
is there any way i can test my maf sensor?? i cleaned it out a month ago when i had to smog it with maf cleaner. when i had it unplugged i noticed the check engine light came one and it was super sluggish. pluged it back in and it was fine again.
ill swap the o2 sensor aswell.

 

Also check the resistance of the CTS...

The biggest things for mileage are:

MAF
CTS
O2S
Vacuum leaks

Any one of the 3 sensors above doesn't read right and you end up using the incorrect amount of fuel. Vac leaks will skew the MAF reading. The IAT and CTS should read close to the same if the engine is COLD.

Also look for fuel leaks around the engine and under the car. And also for fuel in the intake plenum due to a leaking FPR.

 

Got the spark plugs and set timing to the set 10 degrees and now it runs sluggish. Really sluggish... what would be the safest advanced timing without having to worry??

Whats a cts??
How to i check it?
And how can i check if my maf is reading right??

 

10* is stock iirc
did u unhook the est bypass wire before u set the timing ?

its a single wire over the heater box that comes out of the harness tan wire with white stripe if i recall

u have to unplug that wire then set the timing ,then shut the car off and plug that wire back in and restart the engine.

if u set the timing with that wire plugged in it will be way off

12-14* will usually run just fine and not ping

cts is coolant tempurature sensor

maf sensor i know of no real way of testing it as its a frequency type maf , if it was a voltage type u could just check the voltage at idle

 

You need a DMM that will read frequency... I ended up buying one specifically for the purpose of testing my MAF. If you have one, the MAF should be reading about 32Hz at idle. Other than that, the only other way is with a scanner.

Take the MAF out and look at the film inside. If it looks wavy, the MAF is shot.

 

Everyone always misses a huge contributor to poor mileage...Check your transmission. The lockup in the 700R4 is notorious for failure, usually due to solenoid failure. In an older car this is often the likely culprit for poor gas mileage, especially when engine factors have already been ruled out as the cause. Low fluid levels, and burnt (overheated) fluid can cause poor transmission performance as well, leading to bad mileage. Other things to check are front end bushings, bearings, and ball joints, steering components, wheel alignment, and tire pressures. These can all adversely effect mileage.

 

Interesting. Ok so i didnt have that unplugged when i set my timing since i didnt know until i read the manual. Do i haveve to set it back to where it was then redo the timing?? Or can i just reset my computer by unplugging the positive terminal??
Transmission should be good.. i had it rebuilt last year and dont even have 10k miles on it really. Already swapped out fluids in august and the filter. Planning on doing it again in a month.


Ill take a look at the maf again. Last i remember i didnt see film. Is it on the honeycomb? Or on the chip inside??

And cts i replaced last year. Works fine. I have a spare gauge one that i put to make sure it reads properly...

 

OK so i just set the timing back to what it normally was before i touched it. then reset the computer.
tested the timing with both the tan plug on and off and it gave me different readings...
it was weird. with the plug on it gave me about 27 degrees before tdc.... or it would be 27 degrees to the left of my 0 mark on the timing marker tab...
turned off the car unplugged the tan wire then turned the car again and it gave me around 16 degrees...
is there reason for this??
timing is now set to 10 degrees like my sticker says. well at least with my plug off... i didnt test it with the plug on since i got the timing i needed.
got some videos aswell to show..
this ones the plug on

plug off


also when i swapped out my o2sensor, it looked rusty... normal or not??


Thanks -Aaron

 

I get bad gas mileage too but I have recently been letting it run down alot in gas that is. I believe the fuel gauge is off by 3-4 gallons. Last fill up it was just about in the middle of the orange (above E), and I only put 11.892 gallons in. It wasn't stalling around corners. Does that seem right?

I changed everything as well except the MAF sensor. Current MAF on it is a Reman..from Cardone. I think it sucks...who knows...it runs good, idles good.

Another question, I bought an untouched throttle body and the IDLE is so freaking high now..lol..reset the battery and everything..didn't know it was suppose to idle this high. It's untouched...not punched...so I don't assume the presets were different for different years?

 

Unusually high idle could be a vacuum leak, do a gasket check with starting fluid, including all your vacuum lines.

 

No this puppy is sealedddd...my old TB was idling low but it was tampered with. I bought a TB without the idle screw punched out...and its pretty high now...don't know why other than maybe it's suppose to be.

 

The idle speed is usually 1200 (ECM controlled) when cold and 900 hot. Should drop to around 700 when hot and in a gear (auto), or hang around 6-700 (manual).

The film is in the middle of the circuit board inside the MAF, and you need to look through the engine end to get a good view of it. Some MAF sensors have the film at the leading edge of the board (reman junk ), which tends to bend it out of shape.

 

with the new UNTOUCHED TB it is at 1100 hot in gear according to my tach...which I believe is somewhat accurate. I'll have to tach it up with my handheld...I believe I checked my in-car tach with it before.

I took my MAF off and cleaned it once, it looked flat...I think...what do you mean film is on the leading edge? I'll have to check...I have that reman junk in my car now.

Thinking about buying a new AC Delco one from somewhere.

 

The leading edge of the MAF card is the edge closest to the honeycomb. I had a reman MAF that had the film on that edge and one that had it in the middle of the card (like it's supposed to be). That particular MAF failed due to the air passing over the edge of the film, which bent the film up like a skate ramp, so 2/3 of the top surface of the film was in a vacuum with the majority of the air passing over the top edge of the film where it was bent.

 

anybody know anything about the timing thing i was talking about??

 

Yeah...your suppose to set the timing with the TAN PLUG UNPLUGGED to 10 degrees, warm in drive I believe.

100% sure on the unplugged bit though.

 

when u unhook the wire it stops the ecm from controlling the timing.
the reason for setting it to 10* with the wire unhooked is so the ecm knows were it set at.

once u plug the wire back in the ecm takes control of the timing and it changes

say at idle the ecm tells it to have 24 before top dead center
the ecm knows that the distributor is at 10* to start so it adds 14* to bring it to 24*

so if u have the timing set to say 6* with the wire unpluged and the ecm calls for 24* at idle its still only going to add 14* and u will only have 20* total

etc etc

 

How do your spark plugs look? That will tell you if you're running rich or lean.

 

Guess I'll pick up a CTS today. I checked for vac leaks awhile ago, but I'll check again. O2 is new.

I'll try checking the MAF freq too.

My mileage has been going downhill lately too. Suspected my fuel pressure, bumped it up from 32 to 36ish, saw some improvement, but it's falling back to where it was before.

Just put in new plug wires, distributor, cap and rotor. No improvement. (pulse of old dist fins was barely noticeable, and wires were arcing a bit.

 

My bet is on MAF. I have changed every sensor on this car. The MAF is reman...though...from a previous owner buying it. Might need to swap in a AC DELCO unit...

 

coolrims, I'm actually surprised your ECM isn't throwing a code 44 for LEAN mixture. Your fuel pressure SHOULD be 37-47 PSI running.

In your case, I'd definitely look for a fuel supply issue.

:edit: There USED to be a supplier of GM MAFs on eBay, but she may have run out by now. They were cheaper than a NEW off-brand unit. I bought one from her and it worked great until I took my car off the road the following year (stupid rust!).

 

If you don't know how old the oxygen sensor is, then replace it.
My friend replace the leading oxygen sensors on his 1999 V6 camaro and charted a 2mpg increase. The car had more get up and go also.

Cold air intakes tend to reduce MPGs on gasoline engines. The only way to know for sure it A-B-A testing where you establish a base line, install the mod, run it for long enough to get a new base line, then remove the mod and see if MPGs go back to what they were originally.
Its best done with something that has an instant MPG read out, once you have double checked that your instant MPG is accurate.

Removing EGR can also drop MPGs.

 

Hmmm, mayhaps I'll check my fuel pressure again too.

I don't recall really getting a straight answer last time I was asking about it. It was running at 32 (which I thought was low), so I unplugged and blocked the FPR vac line which bumped it to 37 I think. If I check it again now and it's lower again, then that might narrow it down.

It primed to 45 every time and held steady at 41 if I recall. Fuel filter is maybe 10 months old.

A good GM MAF would be nice too. I suspected my MAF a couple years ago. Replaced it with who knows what brand, and 400 miles later it crapped out. I put the old one back in and i'm still running it. Tested the ground, relay, everything, couldn't find anything wrong.

 

Ahhh ok i get the timing set by ecm now.
Plugs look fine according to my haynes manual not hot not blistered etc.
Im going to buy a new maf soon just cuz i have 2 dmms that dont have a Hz reading haha

My cold air intake actually worked well. More power and mpg. I know cuz i tested like you had said the aba setup.
Now im looking into removing the black panel under the car to unbox the filter.

Ended up advancing up to 14 degrees as i wasnt getting the power to drive up the hill to work. Id be punching it and it would lose mph lol!
16 degrees was working really well for power for me but id rather save gas right now haha
Gapped delco plugs did make a differance.I have a smoother idle now and no poppy noises

 

My '92 has a 15.5 gallon tank & usually I get around 14mpg & 16 at best because I like mine to run a little bit on the rich side and stop and go city traffic doesn't get you best mpg. But all those little things can make a big difference and affect your mpg

 

Only on speed density setups. With a MAF or Carb a CAI won't negatively affect it.

 

Idk if those waves on the surface would cause bad gas mileage like you were saying but I just bought a so called new MAF sensor from eBay for 30 bucks it came today. I was just outside removing my old one and putting in my new one...the old one had so many waves! (thanks to the sun being out and bright today I could see them good) on the new one the bottom was FLAT and the top seems to have a bit of a little crease...very small in the corner.

Hope this ups my mileage...I will probably update when I fill up. (I also pulled both fuses by the battery to reset the ECM...I think it is the red & orange one but I am never sure).

 

Awesome. let me know how that goes. im still saving up cash to buy a new maf.

 

The idle is much smoother than it ever was with the new MAF (compared to my old reman one). I use to have a dead spot sort of speak...at 55-60...where I would push the pedal down and it would have a delay in the time in would take to react to my foot. Now, I can touch it a little bit and it goes past this dead spot I had.

No news on gas mileage, haven't got rid of my current half tank yet. I will update in 2-3 weeks. Noticeable difference in acceleration.

 

Still have 1/4 tank on the gas gauge. Drove 175 miles so far. I use to squeeze 200 miles out of 12 gallons which would be in the middle of the orange on my gas gauge. I would say so far, it has to have increased. I will report back when I fill up and empty the next tank (couple of weeks time).

 

Get a T5 I guess, im closer to 23MPG as I only do partial fill ups, so its off a bit, city/highway mix, average of 70-72MPH on eway.

I use to be able to get around 26MPG many moons ago with premium [that was only $1.50 a gal] and cruise speeds under 60 back n fourth to work.

http://www.fuelly.com/driver/350x/firebird

 

http://ecomodder.com/forum/showthrea...eage-7358.html

It would appear the OEMs are using higher flow cooled EGR for more MPGs.
Since I haven't seen a speed dencity fuel metering system on a new vehicle for many years now its safe to say they pretty much all are MAF metered now.

 

I didn't test the frequency yet, decided today to get some multimeter clamps to bite through the insulation, and couldn't find any, so tomorrow I'll find something else to use. Anyway, here's what it looks like.

Slight blacking of the surface down the middle, film is slightly wavy (hard to really tell that much), and looks like a resistor along the side got hot. Blue layer is brown and cracked.
250k miles on this maf. $60 for whatever brand, $150 for AC delco.

 

thats how mine looked but it was a reman unit. switched it and it didnt help anything. guess ill just trace down vacuum lines and make sure everything is plugged in

 

Take the poor thing out back and bury it... It's had a long hard life. It's dead.

That resistor isn't burnt... It's got epoxy or whatever they used to stick the housing together on it. Seen it on several on eBay.

The film, however, is shot.

DO NOT get a "new" or "reman" AFTERMARKET MAF. ONLY get a GM MAF. As I've said many times now, I've had 2 of the aftermarket sensors. Both failed in a year. Neither was built the same as the GM MAF.

Mailman, did you make sure that the MAF was getting power?

:edit: Also, for reference, the Camaro uses GM P/N 25507557 and the Bird 7668... Difference being the elbow glued onto the air inlet for the Bird MAF and Camaros not having the dual snorkel intake..

 

Yes, I know, short reply, but:

Tada! Found the woman selling the GM Bird MAF sensors for $50... She's still got 7!

http://www.ebay.com/itm/PONITAC-FIRE...7db651&vxp=mtr

For future reference, her username is beckysbids...

 

For $50 buy that GM one but I got a good 10 years on an autozone replacement, only odd part I was warned to full disconnect the battery when changing it [both cables] or they would not warranty it.

 

yea its getting power to the maf and the reading with the dmm was more stable on the new one then with the old one. i got a maf from autozone. a new duralast unit.

 

Gumby, was the guy who sold you the MAF going to stand there and watch you put it in? That's the most ridiculous thing I've heard. Worst case, either pull the MAF fuse (the one with the red and black wires next to the one with the red and orange wires) or the MAF relay. You're good.

Mailman, don't forget to reset your ECM. Otherwise the ECM will take forever to recalibrate to the new sensor.

 

Cool, thanks. I see it's the firebird maf based on the part number. I'd prefer the camaro maf because of my setup, but for $50 for the real deal, I'll just cut the bend off again. Now to see if my paypal account even works anymore.

 

someone mentioned the TC lockup I know one way to test it is by running a wire to the top two outside slots on the aldl
here is the link if you are confused
https://www.thirdgen.org/torqueswitch
your tc lockup should be good if when trany hits second or third rpms drop a lot
relay is probably good if in overdrive car acts normal(ie usual rpms at specific speed)

what I don't know is where the relay is so I can replace mine right now I just run w/ tc locked if im going to be doing 30+mph my car is a berlinetta so the relay location might be different from base models I don't know. if someone knows this information im sure it would be helpful to many people

 

A TC that isn't locking up can just about cut the mpgs in half on a truck with a 700R4.
Its not a bad place to look.