So, my gas mileage has taken a SHARP turn for the worse. I typically average 22 mpg with combined city/highway driving. My driving habit havent changed, but my last tank of gas netted me 15mpg, and the last one 6mpg.

Its an '95 auto with 130k on the clock. No check engine lights are on. Checked the tire pressure, and it was fine.

Brakes dont seem to be rubbing. After I drove to work (about a mile) I checked to see if any of the wheels were hot. One was slightly warm, but only luke warm.

I changed the plugs recently, and will probably pull them later today to see if Im running rich.

I do need an oil change, but I cant see that being the cause.

Thanks, and sorry for the rambling post.

 

Might have a leaky injector? A fuel leak?

 

If it was actually running and consuming that much fuel you'd have a pretty nasty exhaust, with almost black smoke constantly coming out.

I call

 

Yeah, you'd notice a severe decrease in performance if it were actually consuming that much fuel, too. I second (3rd?) the fuel leak diagnosis. Look under the car to see if it's dripping anywhere. You'll be able to spot a leak that big. Unless there's a hole in your tank, it probably only leaks (much) when the line is pressurized. If you turn the key to the 'on' (3) position, that should run the fuel pump long enough for you to spot it without having to start the car.

 

what is with these threads with all these mpg issues???

You have to be having some sort of CEL to get that type of mpg. U run any chevron techron? but to get them type of numbers there must be something wrong either mechanically or electronically.

 

Scan for codes, your CEL is probably burned out or diconnected.

 

CEL? What does that stand for? If I had trouble codes, wouldn't the check engine light come on?

@NJMAX you think Im making this up? Why would I do that?

Ill check for fuel leaks when I get home today.

I changed the plugs after the first bad mpg tank, and none of them were black, so I dont think its running rich.

 

CEL = check engine light.

Does the CEL come on when you turn the key to the "on" position, before the car is started?

 

Because it's basically impossible for the engine to be running while 4x the amount of fuel is being delivered/consumed. At that a/f ratio it would be choking so badly that it most likely would immediately foul the plugs and spew black smoke out the tail pipe.

 

CEL = Check Engine Light

 

Check Engine Light.... Duh. Sorry Im tired.

Yeah it works. It comes before I start the car. That was actually the first thing I checked.

 

Yes, I know this. Thats why I was so baffled. I got barely over 100 mile to my last full tank.

It seems it will be that fuel is leaking. I cant see any other way other than not firing on several cylinders with my brakes dragging. And of course then the car would run like crap, have the check engine light on, and have molten hot wheels.

I promise you Im not making this up. Just because you dont believe it doesnt mean it cant be true. Need I cite history?

 

For a typical fill up, you would get about 100 miles per 16.5 gallons. I would need to fill up every other day.


Does it smell like fuel in and around the car?

 

what octane of gas you using? 87? Even that wouldnt cause numbers that low but something wrong.

To get that type of mileage u have to have a CEL or a fuel leak. You are running incredibly rich and the exhaust should be discolored. Or maybe a plug aint firing. You sure u plugged all the connectors in for spark plugs? THat could explain things. Check ignition coils

NO car gets 6.25 mpg unless u running a big block chevy and u not tellin us lol.

 

^No I havent noticed a fuel smell.

It is usually parked on grass overnight. I dont know if that would make a difference.

 

I used to have a leak on the feed line that went into the rail. it would drip only when the car was on(since it would have fuel pressure), my mpg dipped alot(about 7-10mpg) so all I had to do is change the hose and the couplers. if you do have to change any hoses, make sure you get fuel hose tbolt clamps.

 

Read the trouble codes. It's highly likely you've got a bad knock sensor, which doesn't trigger the CEL. But that alone probably wouldn't account for the problem. I recently discovered I had a code for a bad MAF, which didn't trigger the CEL either, so it appears there are more codes than just KS that might be stored.

 

mid grade gas. Yes I plugged all of the coils back in. Even if I hadnt, wouldnt it cause a CEL for a misfire?

To check for a fuel leak I assume I should leave the car on and snoop around fro dripping? Any better suggestions?

 

Park on something solid, like concrete or asphalt and leave the car run. This way you can see a puddle if it forms. Also check under the hood for wetness and smell.

Is it possible to steal gas from the tank with a siphon? Something with a long, flexible tube that would go down the filler neck and into the tank, maybe?

 

Depends on the car. I had a ford escort back in the day. Disconnected one of the cylinders for reasons i wont get into cuz its off topic, but no CEL.

Either way, u gotta park on some street to see if the car is leaking gas.

 

So has this happened multiple times or just once so far? At this point probably the best thing to do is to fill up and see if it happens again. Maybe somebody siphoned your gas or something.

 

So... I think I figured it out.

My odometer isn't reading correctly. It clocked me as having done 29 miles since I filled up this morning. I had driven to school, which is 23 miles each way according to mapquest, and a little running around town which was probably less than a mile.

Im going out on a limb assuming it completely stopped at some point between my last fill up.

Anyone know what could cause this? Are these cable driven speedo/odometers?

 

believe the OP.
i have a 96 auto..143k wit an evap solenoid code
i averaged 8mg,i shud mention tht my valve covers are leaking oil into my spark plug tube so im positive thats my problem

 

The solders on the speedometer circuit board are prone to failure. The speedo has to be removed from the cluster and the solders for the speedo motor, odo motor and the threaded mount lugs resoldered. Fixed my no cruise and P0500 code. My odo was functioning but the motor solders were starting to crack. I had also read of the odo gears slipping on the shaft, especially in hot climates.

If you can have a gps use it as a trip meter and compare. Maybe by a locking fuel cap as well.

If you are parking on grass it doesn't take much fuel to kill grass very quickly if you have a leak.

Good luck,

 

CEL is the car's version of the human Common Sense Light (CSL).

To explain in layman's terms - If we hooked you up to the CSLISC (Common Sense Light Interfacing Super Computer), you would pop/throw/show/etc the following codes:

Failed Search - failure to utilize the search feature on this forum
Failed Eyeball+Scroll - Failure to see the thread with VERY similar name on the same forum page
Failed Logic - your discourse make no sense and confuse smart/learned individuals
Failed Life - failure to execute simple problem eliminating tasks prior to asking others IE: get under the car and look for a leak, look in the engine bay for a leak, go to a local shop and have them run a code check for free, etc
Failed Common Sense - general code for being naive

OK so some of the above is more in jest than truth. Once the idea got in my head it was too funny not to share IMO. That being said, if the boot fits, or in this case if any of them do, some do... trust me, please wear it (learn). </comma rant> GL

 

So wait a minute, you couldn't tell if you drove over a 100 miles when you went to fill up and it was on E and only said 1XX miles on the odometer?

 

Screw off you unhelpful *****. There is really no need to be an ***.

 

I had thought it seemed longer, but Ive been obscenely busy for the last couple months, so I will on occasion screw up little details. I figured I just forgot when i last filled up.

 

damn son lol U had us trippin out bout them crazy mpg numbers


Your instrument cluster is busted. U can try to solder it back up or get a new/used one. Download the FSM from Fallenone and try to troubleshoot. I recommend jus let a mech do it for u or jus leave it. Your mpg numbers are prolly fine

 

That was really funny. I hope it becomes a forum meme!

 

How bad is it to pull the speedo?

I assume essentially the entire dash needs to come out, in which case Ill leave it alone.

Plus, it will be a nice feature when it comes time to sell. (Im joking of course)

 

Searching...there are a lot of threads on how to pull the gauge cluster (How to section, adding led gauges, etc.) The entire dash doesn't have to come out.

Anyway, since I've done it more times than I care to say...there are two screws in the black plastic above the gauge cluster. Take them out, then move your steering wheel to the lowest position. Pop out the trim piece around the cluster (be careful or you will crack it while trying to get it past the steering wheel). Disconnect your switches (cruise, security, dimmer), then remove the three screws (right, left, and top) attaching the cluster to the dash. Once the cluster is loose, pull it out and disconnect the three wire clusters from the back. You should be able to figure out how to disassemble it from there.

 

I would guess down stream o2 sensor and you should try cleaning you tb and maf....idk I did an I have noticed improvements.

 

Downstream o2 doesn't affect MPG, I thought we'd been through this.