No worries. I really didn't know what to do with my first mod.

Yeah, thats what you do. Anytime you make a change to your car's engine you wanna reset the ecu. But be warned that your immediate gains will always be lost or at least diminish without an ecu tune/aftermarket ecu or resetting it again. (or tricking the o2 sensors).

So when you install it and drive youll feel a difference but it will go away eventually.

 

Even if you don't mod your car, you should occasionally do an ECU reset, especially if you bought the car used. The ECU adapts to how the car is driven and if the previous owner used it to drive to and from work mostly during rush hour, it felt sluggish unless I got all the way on it. Resetting the ECU definitely helped drive-ability and throttle response.

Here is the ECU reset procedure:

1. Get in your car, it doesn't matter if you close the door or not.

2. Turn the key to the on (not start) position, the position just before the starter
turns over.

3. Press the gas pedal to the floor with the key in the "on" position.

4. Hold the pedal to the floor for five seconds, then turn the key back
to the "off" position (don't remove the key), then release the gas
pedal.

5. Wait 2 mins. for a full alignment.

6. Drive the car as you always do.

 

So help me understand how this magic happens.

The O2 sensor monitors oxygen in the exhaust and tells the ECU rich/lean. The air intake temp sensor tells ECU incoming air temp, which has a direct relationship to oxygen density. MAF tells how much airflow there is.

If air density goes up, more fuel is required so it doesn't go lean, all of this is kept in balance by the O2 sensor. If the ideal 14.7 to 1 ratio is maintained, cool air means more fuel, more fuel means more power at all throttle settings, all things working like it should.

What I don't understand is how can OBD-II lower power output down the road and keep all these things balanced? #perplexed

 

In regards to the above:

Your generation Accord stores various specific data in non-volatile memory even if there is no electrical power such as when the battery negative terminal or under-hood No. 17 FI Main fuse are disconnected. Only some system stored data is lost when the battery or the FI Main fuse is disconnected. So, pulling the battery cable or the FI fuse will not clear all stored memory such as certain trouble codes, etc.

For the idle learn procedure, the following can be done:

Make sure all electrical items (A/C, audio, lights, etc.) are off. Turn ignition switch to ON (II) and wait 2 seconds. Start engine and hold engine speed at 3,000 rpm without load (A/T in P or N, M/T in neutral) until radiator fan comes on, or until engine coolant temp. reached 194 degrees F. Let the engine idle for about 5 minutes with the throttle fully closed. (If radiator fan comes on, do not include the running time in the 5 minutes.)

Idle learn is generally done when you do any of the following:

• Replace ECM/PCM
• Reset ECM/PCM
• Update ECM/PCM
• Replace or clean throttle body
• Disassemble engine or transmission

 

i was told my factory ecu cant be tuned. anyone know where i can get an aftermarket ecu.

2012 accord lx-s K24Z3

 

@half-fast
Most, if not all Hondas use MAP sensors, no MAF sensors. But in regards to your question, bolt on mods will still make a difference but the computer is constantly trying to keep at AFR to the ideal point. (I hear that in reality the peak power is at an AFR of 12 but 14.7 is the best balance of economy and power). But the process which you described is exactly how it keeps everything balanced. The long term fuel trim is the key to the equation though. It's the learned behavior that allows the ECU to make a biased decision on immediate AFR. It sees how the car has responded to certain load and temp conditions and makes an average that influences the immediate response. All that is lost with an ECU reset and with no learned basis it has to go purely on current driving conditions and the default fuel map.

@wy.moriarty
That's correct, although a few k series ecu's can be reflashed. With basic mods its not necessary to get a tuned ecu. But if you're into further mods then it can be of benefit. Look into Hondata. Or you can do other brand standalone or even piggy back ecus. They get rather expensive though.

 

Starting with the 2003-04 Honda Accord 4 cylinder SULEV, had both a MAP and MAF sensors.

2005 to 2014 4 cylinders have both MAP and MAF sensors.

 

^I didn't know that. Of course the SULEV would explain itself. Did the other K engines have both or just the accords?

 

06-14 Civics and 07-11 Elements had MAF sensors, to name a few Honda/Acuras.

 

Ok. So I guess none of the older Hondas have MAF sensors but they're starting to use them now. i guess for emissions purposes? I know that some Hondas are using wideband sensors now too.