I was just reading about resetting the ECU and was surprised to find there is also a learned memory for the ignition timing.
Your ECU remembers the signals from the knock sensor and makes adjustments to what's called the basic timing advance map. If you had a crappy tank of gas the ECU sees this on the knock sensor output and adjusts the basic timing map to compensate. Obviously, it retards the timing to avoid detonation.
Even if you put a tank of good 94 octane in it won't matter. It takes the ECU a few tanks of gas to compensate for the increased octane and for it to advance the ignition timing accordingly. (relearn the basic map)
When you reset the ECU you erase the "learned" basic spark advance map and the ECU reverts to the using the preprogrammed timing map and comparing that to the knock sensor signal, the coolant temperature sensor, and the crankshaft position sensor to relearn the basic map.
It might be worth a shot if your truck is getting some shitty gas mileage to put some good gas in next time and reset the ECU. You might just see an increase if the learned timing map is retarding the timing too much.
I know I've reset my ECU before and had the gas mileage come back to normal but never knew why. I thought it had more to do with the fuel trim numbers but it seems timing plays a part in it also.
(SC'd guys ignore this and stick w/ Gadget's advice)
Your ECU remembers the signals from the knock sensor and makes adjustments to what's called the basic timing advance map. If you had a crappy tank of gas the ECU sees this on the knock sensor output and adjusts the basic timing map to compensate. Obviously, it retards the timing to avoid detonation.
Even if you put a tank of good 94 octane in it won't matter. It takes the ECU a few tanks of gas to compensate for the increased octane and for it to advance the ignition timing accordingly. (relearn the basic map)
When you reset the ECU you erase the "learned" basic spark advance map and the ECU reverts to the using the preprogrammed timing map and comparing that to the knock sensor signal, the coolant temperature sensor, and the crankshaft position sensor to relearn the basic map.
It might be worth a shot if your truck is getting some shitty gas mileage to put some good gas in next time and reset the ECU. You might just see an increase if the learned timing map is retarding the timing too much.
I know I've reset my ECU before and had the gas mileage come back to normal but never knew why. I thought it had more to do with the fuel trim numbers but it seems timing plays a part in it also.
(SC'd guys ignore this and stick w/ Gadget's advice)
As for the how long it takes to advance the timing I guess I'll find out when I go home. The guy playing with my truck right now doesn't have a diag. scanner that can see anything about timing info in the ECU. I could watch the timing with my o-scope when I get home. I don't want anybody else playing with that though. Cost me too much $$$.
