rich mixture -> reset ecu?

[eswaroop]

Hi,

I think my car is burning too rich a mixture (checked the plugs today, they are buried in a layer of soot) and so is the exhaust. (also noticing loss of power and mileage)

Will resetting the ECU help? If so, do I just disconnect the battery terminal, leave it for an hour and reconnect it?

Also, some threads say that I have to leave the car to idle for 10 minutes for the ECU to re learn the a/f mixture

Is this right?

car is a 99 Accord EX 4 cyl.


Thanks,

Rao

[91lxdreamer]

I dont know the answer to that, but I want to, mines runnin rich too

[SenseiAccord]

most likely ur guys 02 sensor needs to be changed. Most common way to cure the problem. Keep in mind u are suppose to change it every 50k miles or so.

[jcrx]

Dude, you're plugs setup off explosions inside of a small chamber thousands of times every minute, did you expect them to be shiny? And your exhast is routing, well, exhaust, try breathing it, not a pretty picture. Neither is going to look nice.

[eswaroop]

I know they sit in a burn chamber, but I removed the old plugs 15k miles ago to put new ones, and the old ones did not have a speck of soot on them, they were just worn out.

[rubix777]

your car is OBD II so it does not require ECU reset after mods. it'll tune/detune to the mods.

[eswaroop]

Well it is playing games now. When I drive it for some time from a cold start, it has good acceleration. I drive for 20 minutes, stop, switch off the engine and then when the engine is still hot, take it out again, I notice a drastic drop in power..

Is it related to the oxygen sensor and the car going int a closed loop messing things up?

[Tofuboy]

is it related to the oxygen sensor and the car going int a closed loop messing things up?

If you have a problem with the O2 sensor, the system will not go into close loope operation. It will only go into the "limp home mode".

[eswaroop]

Originally Posted by Tofuboy

If you have a problem with the O2 sensor, the system will not go into close loope operation. It will only go into the "limp home mode".

Can you elaborate what you mean by the limp home mode? Also, in this case, would I notice a difference if I just unplugged the sensor?

[Tofuboy]

"limp home mode" is like a fixed program that can not be delete in your ECU. When there is a problem at any one of the componets (depends on what system ex. OBDI, BODII...) the ECU uses to monitor the engine, the ECU detects it and turns on the check engine light, then it shuts off the "close loop operation" and switch to "limp home mode" (LHM).

What the LHM does is to allow the driver to continue to drive the car without maxiumizing the performance of the engine (ex. MPG and HP). It is sort of like a fail safe feature. During the LHM, the engine will run on a pre-set fuel map with lots of limits to prevent the engine from further damage.

The reason the engine seems to run better for you while it's cold, because the ECU detects the temp of the coolant and will run the engine at another pre-set program trying to warm it up to a normal operating temp first before switching to "close loop". Once the ECU detects the engine is warmed up, then it will monitor all the sensors and detects there is a problem with the O2 sensor (if that is the problem, or there might be others) and in your case, switch to LHM.

PS. I should be getting pay for this hahaha

[eswaroop]

Hi,

I took the car to a honda service center today and had them hook it up to a diagnostic unit to see if there is a problem with the o2 sensor. There engine is not throwing any code, the o2 sensor seems to be giving voltages between .15 and .86 volts. The voltage seems to be oscillating around 3-4 times per second. How can I detect if the sensor is just sluggish?

One thing I noticed was that the ignition timing advance was around 10 degrees during idling (just out of spec of 11 - 13 degrees), and when the throttle is given, it goes up to around 14 - 15 degrees.

Isnt that a little less for this engine? I am not sure but it sounds too advanced. I am using premium fuel, but that should not advance it too much...

The diagnostic unit says that the Ignition advance is determined by the ECU... so what is happening?

thanks

es

[Tofuboy]

I took the car to a honda service center today and had them hook it up to a diagnostic unit to see if there is a problem with the o2 sensor. There engine is not throwing any code, the o2 sensor seems to be giving voltages between .15 and .86 volts. The voltage seems to be oscillating around 3-4 times per second. How can I detect if the sensor is just sluggish?

Is this "diagnostic unit" a scanner? if so do you know what model is it? Cause some scanner will only show you the min. max. and average of the voltage the O2 is producing not the actual cycle that you can see with the time line adjustment. Anyway, if your O2 is only oscillating 3-4 times per second during idle than it's sluggish. It should cycle around 150ms.

PS. sorry for the late reply, I am addicted to FF XI