Extremely bad MPG in a 98 GSR

[cizkaro]

I am sure this has been posted a million times. I have a 98 GSR with headers and a sports cat and stock intake. This car is destroying my pocketbook on gas!!!!! maybe 19 mpg highway if im lucky with normal driving. Ive tuned it up with plugs and wires, upon inspection the caps and rotors seem fine and look new checked for leaks, run fuel system cleaner, I have not put a fuel filter in it but dont understand how this would kill my mpg so badly and I have no check engine lights. All I can say is spending 40 dollars to fill up evey 160 miles is making my life as an unemployed job seeker really difficult because of how far away I live from the city.

 

[xxBLOOD88SHOTxx]

What do your plugs look like when you pull them out?

Do you have them gapped correctly?

Youre sure your CEL works?

How does the car run/drive?

 

[NemesisCBR]

How are you sure its been posted a million times? Did you look? When did it start happening? What changes were made prior or around the time? Fuel filter filters fuel so what do you think could happen to a filter that carries your fuel that may affect mpg? There are a number of things that can affect gas mileage so either you back track to when it started and work from there or start checking off the entire list of random things. I suggest a more logical approach. Providing a lot of detail/description often helps.

 

[cizkaro]

its been this way since i bought it in November 2012 after the bank took my house and my car. I have no clue I am not a mechanic. I am just looking for help narrowing this down. I have no idea if my CEL works. plugs are gapped and good the usual tan/brown color except cylinder 3 which has an minor oil fouling problem from bad rings. Again I am not a mechanic I dont know what details are needed. My compression is spot on at 220ish PSI my head was rebuilt just 3 months ago. the car runs smooth and strong drives the same no idle jumps nothing.

 

[mikeman990]

Might be running rich check your o2 sensors and is there a check engine light?


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[cizkaro]

Mikeman I have no CEL coming on but i have considered the o2 sensors but my father is mechanic and always taught me if they fail the CEL will come on. when running the only thing it does is stutter every so slightly on occasion during idle.

 

[zack11122]

The bulb might be out. Bring it somewhere and have them check for codes.

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[cizkaro]

ive had my obd2 reader on it recently. no codes

 

[xxBLOOD88SHOTxx]

Bad rings in a cylinder, but you have spot on compression? If oil is making it past the rings that is not a minor problem. Do you have a lot of blow by?

If you FEEL a sputter here and there and you say one plug looks odd, then it would be time to check EVERYTHING on that cylinder to rule it out.

You ever check mechanical/ignition timing?

 

[AcuriousLegend]

Have you checked your tire pressures? Do you idle in traffic a lot? My mileage went from low-20s to mid-20s when I added in a few PSIs. Got stuck in traffic once for three hours and my MPGs dropped to something like 19 highway.

Spending time past 6K will also not do your fuel economy any favors.

 

[cizkaro]

Bloodshot the compression rings are good. oil control ring is bad in cylinder 1 im guessing since the head was rebuilt 3 months ago and the bottom end hasnt been touched due to money. even before the rebuild my MPG was wretched cylinder 3 was 12 psi from a stuck valve now all cylinders read 220ish psi. So unless the head i paid lots of money to be rebuilt professionally is wrong dont ask me where the oil is coming from. Again not a mechanic. Timing has been done twice since i owned it once by me and once by a mechanic. I know the car is likely really f-ed up but Im just trying to save myself money so i can get it fixed correctly. But everybody wants 2-3 grand to rebuild the motor completely. And its hard to justify spending the assessed value of the car in good shape to fix it when its not worth that much. I bought it becuase i honestly had no choice and its all i could find i could afford as it didnt run and sold to me for 600 dollars and i spent roughly 400 dollars to get it where it is now. My home + my car were taken by the bank in 2012. ANd since then ive just been stuck with a car that consumes a quart of oil a week by burning it and vomiting out the back of the motor somewhere near the head block meeting point but that is another story. I am about ready to give up and sell it for scrap I am just so tired of one problem after another. this car is a piece of sh*t. and getting 160-180 miles out of 13.5 gallons of gas is bs from a 1.8 my 5.7 liter pickup got better gas mileage and it was only a year newer

 

[cizkaro]

Have you checked your tire pressures? Do you idle in traffic a lot? My mileage went from low-20s to mid-20s when I added in a few PSIs. Got stuck in traffic once for three hours and my MPGs dropped to something like 19 highway.

Spending time past 6K will also not do your fuel economy any favors.

Tire pressure is good. I dont idle alot as most of my driving is highway I dont rev over 4k normally

 

[xxBLOOD88SHOTxx]

Bloodshot the compression rings are good. oil control ring is bad in cylinder 1 im guessing since the head was rebuilt 3 months ago and the bottom end hasnt been touched due to money. even before the rebuild my MPG was wretched cylinder 3 was 12 psi from a stuck valve now all cylinders read 220ish psi. So unless the head i paid lots of money to be rebuilt professionally is wrong dont ask me where the oil is coming from. Again not a mechanic. Timing has been done twice since i owned it once by me and once by a mechanic. I know the car is likely really f-ed up but Im just trying to save myself money so i can get it fixed correctly. But everybody wants 2-3 grand to rebuild the motor completely. And its hard to justify spending the assessed value of the car in good shape to fix it when its not worth that much. I bought it becuase i honestly had no choice and its all i could find i could afford as it didnt run and sold to me for 600 dollars and i spent roughly 400 dollars to get it where it is now. My home + my car were taken by the bank in 2012. ANd since then ive just been stuck with a car that consumes a quart of oil a week by burning it and vomiting out the back of the motor somewhere near the head block meeting point but that is another story. I am about ready to give up and sell it for scrap I am just so tired of one problem after another. this car is a piece of sh*t. and getting 160-180 miles out of 13.5 gallons of gas is bs from a 1.8 my 5.7 liter pickup got better gas mileage and it was only a year newer

If the plug is getting soaked in oil, then it wont fire correctly/completely and it wastes fuel. Improper combustion equals loss of power which equals shitty MPG. Youre asking what the issue could be and this could very well be the issue.

OR

How do you know it is being fouled from oil? Maybe you have a stuck injector and you're running rich in one cylinder and that is why it is turning black? Is the plus itself wet/coated in oil when you pull it out?

Is this thing smoking at all when it runs?

 

[cizkaro]

It's defiinitly oil all over the plug the smell and texture gives it away. It smokes sometimes while warming up and anytime I rev it high.

If the plug is getting soaked in oil, then it wont fire correctly/completely and it wastes fuel. Improper combustion equals loss of power which equals s***ty MPG. Youre asking what the issue could be and this could very well be the issue.

OR

How do you know it is being fouled from oil? Maybe you have a stuck injector and you're running rich in one cylinder and that is why it is turning black? Is the plus itself wet/coated in oil when you pull it out?

Is this thing smoking at all when it runs?

 

[xxBLOOD88SHOTxx]

Are the threads covered in oil? There is a spark plug gasket that can leak oil all over the plug and foul it out.