alarose64

Hey guys.

I have a bone stock 01 AP1 with 117xxx miles. I noticed that suddenly I was getting very very poor gas mileage on the highway, like about 15 mpg. I confirmed this on my trip from New Jersey to Virginia, where I averaged 15 mpg. I have no CEL, but I can smell that it seems to be running rich. I also noticed the idle sounds deeper and rougher. I tried to check my AFR using the Torque app, but all I saw was the O2 voltage jumping between 0.2 and 0.8 V on the highway while cruising. I guess this is all the info you can get from a narrow-band sensor.

I have an autocross coming up in a week, so I really need to figure this out asap. I am tempted to throw an O2 sensor at it to see if it fixes the problem, but I figured I would check in with other s2000 owners to see if they ever had a similar problem.

shiv

Have you adjusted the valve lash? I was having similar symptoms, turns out the valves were way out of spec. Fairly easy job to do, and made a world of difference.

Kenny_Stang

Good idea to also check your catalytic converter (if you still have it in place), they tend to get clogged over time and also break up and can cause similar issues. Even if there is no check engine light, there may still be some codes being thrown, doesn't hurt to take it to AutoZone for a free code read.

alarose64

I did a valve adjustment a few months ago, but I guess I could check it again. Also, the torque app didnt show any fault codes. Would autozone's scanner pick up on something an obd2 scanner wouldnt? Thanks for the input guys.

windhund116

Did you pull the spark plugs and have a look-see? One cylinder maybe not firing correctly --- for whatever reason.

VTEC4-2

Make sure nobody has jammed fruit or vegetables in your tailpipe.

Could your air pump be running constantly, thinking the cat needs to be heated? If your car continues to do this, it would result in extra consumption because extra fuel is delivered during this heating mode.

Utah S2K

How do the plugs look; as previously noted?
Utah

S2kJoshh

Yeah as previously stated check your spark plugs. I was getting 14-15mpg highway too. Horrible mileage. Changed my spark plugs I'm at 23-24mpg

rpg51

Brake dragging?

jyeung528

there are way too many variables that affect gas mileage, but what you're getting is very bad.

i would suspect plugs or straight up fuel leak or don't go back to the gas station you used for that tank.

tire pressure, alignment, map sensor, air filter, catalytic converter, bad gas, valve issues, oil sludge

let us know if you find the culprit(s)