travisl1213

why would my check engine light come on when im running 87 octane but not come on if i use 89 or 93.
i think it just has expensive taste, lol. i dont have a prob running higher octane i was jw

hammeron

perhaps the timing has been advanced and/or it's
tuned for a higher octane

travisl1213

idk when i bought it it had weld in flows and shorty headers, but thats it, well i thought

travisl1213

any other ideas

bluepony4.6

Have you already looked to see if you have a chip on your computer?

travisl1213

where would i look, there isnt anything in the cpu plug in under the steering colum

ShadowDrake

To check for a chip you'll have to remove the passenger side kick panel and take a look at the ECU itself... what's the code say when you run 87?

travisl1213

last time i checked it was an O2 code

ShadowDrake

I'm at a loss as to why it's happening but then again I didn't get a specific code. I'm guessing it doesn't run any different with the code up.

If you're looking for the ECU it's a silver box and it's right behind the kick panel (pull around edges of panel and it will pop off)... there should be an access port somewhere on it, if there's a chip sticking out of it, that would be it... but if I'm not mistaken Ford removed the access ports in 98 and up... I've got a diablosport book on it around here somewhere.