I just ran out of gas today at only 156.8 mlies traveled. I have major issues with this. what would explain such horrible mileage?

I used to get between 300-350. than there was the accident which necissitated the removal of the hood/bumper. the car sat for a year after that, and was brought back in to service about 9 months ago, at that time I was getting round 250 to a tank. but 150 is nuts, there is no reason for it, the car runs great, idles solidly, and shows no signs of being out of tune, or any thing, and as I sit her on the side of the road, I can't help but wonder what's wrong! I have been thinking of replacing the o2 sensor, plugs, I have 8mm wires on the way, and I considered changing out the coil for an msd one. would any of that help?

------------------

1987 Pontiac Fiero GT, 148,000 miles! decklid window, silver guages. rear ended someone, and now the rebuilding starts! More pics of my 87 GT can be found here
1985 Pontiac Fiero 2m4 auto, 222K miles and counting <-my first car, and i still cant get rid of her!
2002 Toyota Celica GT, 5-speed, 47K miles <-FOR SALE!
A 4 year olds knowledge of science: No matter how much jello you put into a swimming pool you still can't walk on water.

Just a guess,possibly thieves are ripping you off (get a locking gas cap).

Kevin, of course it would all help, but not to the extent of fuel your burning through - I would check for vacuum leaks on the MAP curcuit, or possibly a MAP sensor on it's way out. This is also commonly seen after putting in a low temp thermostat/fan switch - the comp is constantly DUMPING in gas to bring the temp up, but wont go up due to the action of the low temp parts

------------------
Former West Coast Fiero Employee

New and Pre-Owned Auto Sales Consultant
Power Ford Valencia

I was going to suggest the temp also. When my stats have gone bad and the engine runs lower it really kills gas mileage.
Add maybe you O2 is leak.
Winter fuel is poorer.
After setting you could have an injector leaking or stuck. Have you done a fuel leakdown test with a pressure gauge.?

Gas leak? You ever smell fuel when the car is running? How about someone else driving your car and resetting the odometer? (Funnier things have happened, especially if you have teenage kids)

My 86 GT runs very well and passes emissions with flying colors. My range on a full tank is around 200 miles at best. It's tough on long runs out west where gas stations can be far and few in between.

Ted-
Were you seriously pulling 350 miles on a tank before? That's crazy! One thing that really caused my 2.8 to gulp rather than sip was an old, burned O2 sensor. $30 was a small price to pay for mileage.

------------------
If you can't be good, be good at it.

He must be talking about the 2m4. Although even at 32mpg it would be stretching it for a duke. I get 32 in mine on long hauls at 70mph. To all of a sudden get 15mpg makes me wonder if the O2 sensor might be bad and showing a lean condition to the ECM.

I'm with ya, Hudini, I smell a bad O2. Although I got 30 mpg regularly with an 84 pukin duke which only had four forward gears, so I imagine 32 isn't too unbelieveable with DIS and a 5th gear... Man I really want an 88 manual coupe...

------------------
If you can't be good, be good at it.

I would like to see what the computer is saying about this, did you pull the codes yet?

Lots of stuff to check such as tire pressure, air filter, gas filter, O2 sensor, clogged cat, sticking thermostat (open loop), alignment, fuel injectors. Have you switched tire / wheel combinations lately to a larger / wider size? Torque converter locking up properly on automatic transmission? Trip odometer sticking?

A good tune up is a great place to start. An auto scanner is handy to see what the engine sensors are doing, especially the O2 sensor. Have you got access to a scanner?

Hope you get the difficulty solved soon, those gas prices ain't cheap theses days.

quote Originally posted by Hudini: Gas leak? You ever smell fuel when the car is running? How about someone else driving your car and resetting the odometer? (Funnier things have happened, especially if you have teenage kids)

no one, BUT NO ONE, drives my car BUT me!!! EVER!! so not a chance. and nope no fuel smell.

With a SLUSHBOX no less? The TH125C? That is amazing mileage, even with an 87's larger tank. You have/had a sweet little motor there. When did you last replace your O2?

------------------
If you can't be good, be good at it.

quote Originally posted by fierodeletre: With a SLUSHBOX no less? The TH125C? That is amazing mileage, even with an 87's larger tank. You have/had a sweet little motor there. When did you last replace your O2?

this engine only had 54K original when i got it. she currently sits with 65K now, sweet, yes!

i would have to assume the o2 sensor to be the original one, which would not be a stretch, so i would say its probably time. so, does delco make one still, or would a bosch one be good enough? are there any better ones out there?

im also gonna replace the fuel filter soon, 12k should be the life of one of those right? i put it in when the motor went in.

[This message has been edited by tednelson83 (edited 12-15-2006).]

Brake calipers sticking?

quote Originally posted by 30+mpg: Brake calipers sticking?

checked them when i did the struts on tuesday.

I got one thing for you to check that others have not mentioned....


A stuck caliper. if one of your calipers get's stuck even a little bit it will kill your gas mileage (and make all the grease in your bearing on that wheel disappear)

Had that on a Pontiac transport. Never felt a pull in the steering, went to get the wheels rotated and the front left rotor was almost gone as well as the pads. Fixed the brakes and my gas milage jumped way up.

quote Originally posted by jetman: I would like to see what the computer is saying about this, did you pull the codes yet? Lots of stuff to check such as tire pressure, air filter, gas filter, O2 sensor, clogged cat, sticking thermostat (open loop), alignment, fuel injectors. Have you switched tire / wheel combinations lately to a larger / wider size? Torque converter locking up properly on automatic transmission? Trip odometer sticking? A good tune up is a great place to start. An auto scanner is handy to see what the engine sensors are doing, especially the O2 sensor. Have you got access to a scanner? Hope you get the difficulty solved soon, those gas prices ain't cheap theses days.

Oh, yes, good one jetman, TCC gone bad can make the car run much higher rpms. You got ALDL cable and software to check what the ECM is seeing?

i have the parts to make the cable, but hav'nt done it yet.

quote Originally posted by tednelson83: well, i checked it, and all i saw was a code 12, so all is well in the ECM department. i stopped by the parts store on the way home and grabbed an o2 sensor, and a recharge kit for my K&N.

K&N Filter could be the problem if you haven't had it long. They plug up quick and all at once it seems. I think there was a good write-up on the subject of paper air filters vs. K&N types somewhere on the forum.

------------------
Zefyr - Las Vegas
'86 GT 3.4L 5spd Turbo, down for rebuild. 'sleeper'
'85 SE R.I.P.
'85 Turbo 2.3L Ranger 'dirt'
'80 AMC Concord 2dr 'slider'

quote Originally posted by Zefyr: K&N Filter could be the problem if you haven't had it long. They plug up quick and all at once it seems. I think there was a good write-up on the subject of paper air filters vs. K&N types somewhere on the forum.

well, it came with the car, and i've had it over 3 years now. yes its been cleaned before, but its been a bit.

NGK Spark Plug: Plug No. UR5GP G-Power Platinum Plug; UR5GP; @ Gap .045 $2.98 <== 3 month warranty
NGK Spark Plug: Plug No. UR5IX Iridium IX Plug; UR5IX; @ Gap Preset $6.96 <== 2 year warranty
NGK Spark Plug: Plug No. UR5 V-Power Plug; UR5; @ Gap .045 $1.77 <== 1 year warranty

The above according to Advance Auto Parts web site.

wow, noticeable power increase after cleaning the air filter, changing the o2 sensor, resetting the computer, and steam cleaning the engine.

Tomorrow: changing the plugs, replacing the coil, checking the timing, and seafoaming the engine.

when they arrive: changing to 8mm accel spark plug wires. shecked the cap/rotor yesterday, and it was good, so im leaving it.

Any update? How she running after the tune up?

feels like i just added 10 hp! runs nice and smooth now, though i did have to fill it up with 89 octane this time sence the station i went to was out of 87, thats something i have never done, so i wonder if that may play a role. i still have yet to check the timing, seafoam, or get that msd coil, but i did the wires and plugs, and i gotta say, those red 8mm accell plug wires match the engine red perfectly, and look GOOD!

What was the end verdict, did the tuneup + airfilter restore your amazing gas mileage

Very odd... my car's getting about 13-15 MPG too - and it's exactly the same car. New plugs, new wires, cap, rotor, ignition module, pickup coil, O2 sensor, MAP sensor, IAC motor, umm... pretty much everything new. Except the air filter. Would that really make a huge difference??

------------------

'87 Fiero GT, Automatic, 153k miles, stock everything, just trying to make it all work again.
Shameless self promotion: PIP giving you problems? Check out http://hostfile.org!

yes, depending on how bad it is.

a clogged air filter not only chokes the throttle, creating a rich burn sitiuation, but manifold vac won't be relieved when you open your throttle, meaning that the egr and other systems will still be in operation. since EGR retards chemical ignition, it reduces your power output, and hence you use even more foot just to accelerate to cruising speed. everything's related, there are seldem few parts on an engine that are not interdependant

quote Originally posted by Falcon4: Very odd... my car's getting about 13-15 MPG too - and it's exactly the same car. New plugs, new wires, cap, rotor, ignition module, pickup coil, O2 sensor, MAP sensor, IAC motor, umm... pretty much everything new. Except the air filter. Would that really make a huge difference??

Definitely. Especially if it looks like this...


(Came with the car, replaced right away)

OMG.... wow, no... mine looks much cleaner than that. It actually looks very clean and seems to flow freely (just checked it out). However I did find more melted vacuum hoses... UGH. The hose coming off the throttle side of the plenum, which curves down past the EGR hose, is now plugged as well. Looks like the only place it goes is the cruise and the vapor canister though. I guess that won't hurt fuel economy... but I still don't know what will.

Old coil, maybe? Be a good investment to buy a new coil? *shrug*

something i'm suprised no one picked up on....change your oil lately? this can be a huge cause of lost gasmilage, and with the SLUSHBOX Th125 get your tranny flushed and cleaned out...big improvement there as well... atleast there was in mine.

- Phil

------------------

"When enough is enough, thats when you know.....your halfway there"

quote Originally posted by DMaxME: What was the end verdict, did the tuneup + airfilter restore your amazing gas mileage

dont know yet, haven't had to fill up yet, but im at 95 miles now. ill keep you posted.

hmm, just put 8 gallons in at 117 miles, so round 14mpg, which is better but still crap. the timing was set at 12 so i lowered it to about 9 (was bouncing between the 8 and 10 marks) which i figure was good enough. have not had a chance to replace the coil yet, but i dont know if i should expect much from that. where else can i look, i have lasted all i have done.

i am looking at a set of 3.1 injectors on ebay to go in when the 1.6 roller tips go in. thinking perhaps there is a leaky injector. someone suggested a leakdown test...question...how?

EDIT:before someone comments,...yes i grounded the ALDL and checked timing in drive.

[This message has been edited by tednelson83 (edited 12-23-2006).]

Just found a great way to calculate my mileage on the fly: top off at the pump (er, til it clicks), run a calculator on the trip meter divided by gallons pumped, then reset the trip meter. Last two readings were 15 and 17.1 MPG.

Yep, I'm definitely watching this thread...

edit: Yes, I realize that's a method everyone already knows about. I'm just saying that I just found it for myself...

[This message has been edited by Falcon4 (edited 12-23-2006).]

how do you think I was able to tell you what my mileage was?

Hrmm. Maybe the Kuhneutson valve...?