extreme fuel consumption

[andrewgrant]

i have a 1995 grand prix with a 3.1 that is getting somewhere near 6 mpg. I am baffled at this, as I have never seen a mileage drop like this on any vehicle. I have replaced the spark plugs, wires, air filter,oxygen sensors, and cleaned the entire fuel system,and i still get the same. Does anybody have any other ideas?

[85_Olds_Ciera]

i still get the same. Does anybody have any other ideas?

Does Midnight Auto Supply cruise your neighbor after midnight, with their Arkansas Credit Card?

Is there black smoke coming out of your exhaust? If so, find the temp sensor for the computer, and replace it....or scan it, and see what it says for engine temp.

[IsaacHayes]

Yeah coolant temp sensor would be the next one to replace. How is the power?

[3400-95-Modified]

Also think of Ignition module or coils Being a 3.1 they are under the exhaust manifold and those definately have a tendency to heat up and go bad quick.

[sharkey]

another thing to check is your fuel regulator, pull the vacume line off and if fuel comes out, its bad. id also check the fuel pressure and consider having the injectors cleaned. another idea is to pull the plugs out again and see if one plug looks washed or extremly rich, that would lead you to one hole.

ill 3rd the temp sensor. if the pcm thinks your at -40f all the time it will eat tons of fuel.

[IsaacHayes]

Ah yes forgot about the FPR! How did the plugs look?

[Joseph Upson]

I would have the ignition module checked and possibly the coils. When I lost nearly 10 mpg on a distributor engine it was a bad coil arcing all over, the car was a little sluggish also. I wouldn't use anything other than GM parts for my ignition system after my experience with bad modules from name brand stores including NAPA.

You can find several posts on the Fiero Forum where some of the cars just refused to run consistently on aftermarket ignition modules including mine, although it's possible the distributor could have contributed to it, when the GM part went in my car as well as others the problem went away and there was a noticeable performance increase on acceleration and I could demonstrate it by swapping in a known good Autozone module.

If you could put a timing mark on your balancer and check it with a timing light that might show wether your timing is even advancing like it's supposed to. A bad module will not always trip the SES light.

[PCGUY112887]

Do you have a locking gas cap?

[IanSzgatti]

im putting money on either a leaking fuel tank or a leaking fuel line. go down under... 6 mpg is like a godamm sherman tank

[85_Olds_Ciera]

6 mpg is like a godamm sherman tank

454 dually GMC pulling a horse trailer....before fuel injection....

[IanSzgatti]

454 dually GMC pulling a horse trailer....before fuel injection....

... crammed full of horse meat

[andrewgrant]

i do have a locking gas cap, people were taking gas before, i have already checked the tank and lines and everywhere else for leaks, there were none.i replaced the temp sensor, it took mileage back up a little, but its still pretty bad. my 5.2 liter pickup still gets better mileage. And someone asked about power, and i have to say its low on it.

[85_Olds_Ciera]

i replaced the temp sensor

Which Temp Sensor? The idiot light's temp sensor don't count...

You need to have it scanned...and see what the temp is...assuming your thermostat is working correctly.

[IanSzgatti]

the thing is here we could all list off every sensor this thing has... MAF, MAP (if this 3.1 has both) are good ones to inspect. You simply need a digital multimeter and some values to check against. For the MAF, try tapping it lightly and note any idle changes...
it's difficult because you'll be pointed in a million directions here.... You need to have the vehicle scanned, your obviously running extreamly rich, so you'll expect to see minus values for LTFT... the PCM undoubtedly knows your running rich, but if it hasn't thrown a code then that means your fuel managment has been able to compensate enough for the condition....

no vac leaks... no physical damage to lines... new temp sensor... hmmm, Look, when you say it's real low on power... does the power you DO have feel even, or do you feel a little something like a misfire, or the feeling when you have a bad coil...? Also...how does the vehical IDLE? if the MAF, injectors, FPR check out, you could have physical damage to the valves or pistons... you should do a compression test as well...

[85_Olds_Ciera]

... crammed full of horse meat

Saddle bred horses....