Question about fuel

[CARGUY40]

I just bought a 1999 Oldsmobile lss supercharged and im not sure what kind of gas did the previous owner put in it but its suppose to take premium and some guy in the Oldsmobile forums told me to do this since i dont know what type of gas previous owner put=

Disconnect the battery for minimum 1/2 hour to reset the pcm so if its been run on lower octane and defaulted to the low octane table it can return to the high octane table for some extra timing advance as well as to reset the fuel trims.

Wouldn't the computer see a higher grade gas without doing what he told me to do? Can i just get the gas to near empty and fill it to full with premium?

 

[zach1900]

Nuts. If the engine detects detonation on lower octave it will adjust the timing on its own. My old Maxima V6 did this when. I think every car made in the last 30 years can do this.

 

[zach1900]

People are so goofy about computers. Low octane table? Lol. More like if the engine detects knock it will retard the timing ,the knock sensor or computer don't detect what kind of gas you have it just detects knock or it doesn't. Simple.

 

[Clevy]

Why did he want you to reset the fuel maps. That makes absolutely no sense whatsoever.
As zach already said the engine has a knock sensor that amuses timing for the fuel used. Whether you use premium or regular won't matter to the engine since it will adjust based on knock,however if using regular power output will be less.
Use premium if it was engineered that way for maximum performance. And premium has more detergents usually too keeping the fuel system and combustion chambers cleanish.

And just for your own info you did t have to reset the ecu. The ecu tests the fuel on every start up. It advances the timing til it senses knock,then retards it slightly to maximize performance at every start up. What the previous owner used is irrelevant since the ecu checks knock every cold start.

 

[bullwinkle]

'99 should be OBD II, it would probably require a scanner to reset everything. Just throw in a tank of good premium (like Sunoco Ultra 93 or similar) & see how it runs.

 

[eljefino]

There is something to this. I had a saturn that would gulp some oil taking off from a red light and it would distort the knock table, for the worse, for around 200 miles. Oil of course being very low octane.

Just run good octane and it will earn it back.

 

[Kestas]

Originally Posted By: zach1900
Nuts. If the engine detects detonation on lower octave it will adjust the timing on its own.... I think every car made in the last 30 years can do this.

Only cars with a knock sensor can do this. There are many cars made in the last 30 years that don't have knock sensors.

 

[raytseng]

I wouldn't be so quick to jump on the guy.

Some cars adjust the throttle and power response over time to match the driver habits.
It is only slightly correlated to the fuel as the power output due to premium fuel.
So id say they are right but for wrong reasons.
Resetting the ecu gives you a clean slate for it to learn your pedal stabbing habits immediately.

Definitely some folks who both fuel up with a tank of race fuel for a once a year track day in their luxo sedan and also reset the ecu so it doesn't think their doing the same errands as the previous 364 days of daily driving and gives them full power insteadly instead of eco and smooth mode

 

[CARGUY40]

Ok....

 

[CARGUY40]

My car does have a knock sensor.

 

[eljefino]

Originally Posted By: boostedtsiawd
My car does have a knock sensor.


Pretty much any forced induction one will. The 1977 Buick Regal Turbocharged 3.8, what turned into the Grand National, had a carb, turbo, and knock retard!

 

[CARGUY40]

.....

 

[Joel_MD]

Originally Posted By: zach1900
People are so goofy about computers. Low octane table?

Yes, the "low octane table" is next to the little laboratory that continually conducts a spectral analysis of your oil so it knows when to flash the "change oil" announcement on the dash.

 

[eljefino]

I have seen learned behavior. Comes across as "flat spots" accellerating. Often right at 2000 RPM. It may not be a table, but it is a misplaced salad fork.