What causes a rich idle?

[yukon]

1993 240sx

I keep getting the leaky injector code during idle. especially when the car is really warmed up. i clear the code and it immediately pops back up. the O2 sensor bounces around a lot when car is warmed up and idling. a recent smog test said i had high hydorcarbons at idle. I passed by skin of my teeth.

Would it help to advance timing? Im idling around 700 at the moment. my injectors were replaced a couple of years ago. i guess to oring could have slight leak that is getting worse with time.

[boosted armo]

you're saying your wb02 is bouncing around. when was the last time you changed your primary o2?

[yukon]

you're saying your wb02 is bouncing around. when was the last time you changed your primary o2?

The o2 sensor is new. I think the O2 sensor does not start reading right until the car is warmed up. It wont get hot enough if you idle for very long. it goes stoichastic during idle if ive been driving and then stop. not sure if the computer is monitoring o2 sensor during idle or if it just goes stoichastic without input from o2. i get the feeling you know nothing about this subject. the o2 sensor is ignored during idle so it is not the problem.

[steve shadows]

1993 240sx

I keep getting the leaky injector code during idle. especially when the car is really warmed up. i clear the code and it immediately pops back up. the O2 sensor bounces around a lot when car is warmed up and idling. a recent smog test said i had high hydorcarbons at idle. I passed by skin of my teeth.

Would it help to advance timing? Im idling around 700 at the moment. my injectors were replaced a couple of years ago. i guess to oring could have slight leak that is getting worse with time.

Bill Nye voice - "I'm Glad you asked Timmy,

a rich idle is caused by

1. improper function of IACV
2. cold start with bad 02 sensor
3. improper ignition firing or not working correctly
4. having your base ignition timing too advanced
5. a vacuum leak can also cause either too lean or too rich of idle

[ManoNegra]

you keep getting a leaky injector code...
that should tell you to check for a leaking injector
since that will make your car run rich no?

a properly function o2 sensor will oscillate between a lean/rich condition ~5 times per second
they're designed that way
it always reads properly
ecu starts making corrections once it reaches close loop
which is typically less than a minute

stoichastic? wtf
are you referring to stoichiometric combustion?

seriously both of you "know nothing about the subject".
do yourselves (and the community) a favor and take an OBDII class
stop spewing nonesense.

[yukon]

you keep getting a leaky injector code...
that should tell you to check for a leaking injector
since that will make your car run rich no?

a properly function o2 sensor will oscillate between a lean/rich condition ~5 times per second
they're designed that way
it always reads properly
ecu starts making corrections once it reaches close loop
which is typically less than a minute

stoichastic? wtf
are you referring to stoichiometric combustion?

seriously both of you "know nothing about the subject".
do yourselves (and the community) a favor and take an OBDII class
stop spewing nonesense.

the leaking injector code means too much fuel which can mean a lot of things. i have passed smog with this code. im not even certain if it is abnormal for a car of this age to throw this code because the idle is designed to be rich.

I'm pretty sure the O2 sensor is ignored by computer below a certain RPM.
(i might be wrong about this even though the fsm says this.)
That is why Im confused when idle goes stoichiometric during idle when really warmed up after long drive. A car won't go closed loop after a minute or even afte 30 minutes if you sit there idling. The o2 sensor will never get hot enough during idle. The ecu will only start acceptin inputs from O2 sensor if they make sense and they dont make sense during idle.

Your information is generic as hell , my friend. my car is obd 1. of course the o2 voltage oscillates between lean and rich when mix is optimal and o2 sensor is warmed up sufficiently. thanks for stating the god blindingly obvious. my 02 sensor oscillates lean/rich at idle after long drive but then starts fluctuating between .4 and .6 volts.

[Bigsyke]

A code 34 will make you run hella rich.

arent you supposed to check for a leaky injector?

The o2 is never ignored, ever. It may not directly control engine operation untill it recieves a signal from the CTS. Only thing that is controlled below a certain RPM is fuel cut, its directly in the FSM.

The primary o2 sensor doesnt register heat, its ussually 1 sheilded wire, thats triggered by the CTS. Yes it will go into closed loop operation within 1+ minutes depending on your cooling system. How do they not make sense durring idle? your using a pepboys o2 gauge huh. Ignore the o2 sensor, mine is probably bad from all the seafoam and marvel mystery oil ive used throughout my operations. The o2 has nothing to fucking do with your fuel system code.

[yukon]

Bill Nye voice - "I'm Glad you asked Timmy,

a rich idle is caused by

1. improper function of IACV
2. cold start with bad 02 sensor
3. improper ignition firing or not working correctly
4. having your base ignition timing too advanced
5. a vacuum leak can also cause either too lean or too rich of idle

o2 sensor is ignored by ecu when it is cold which is basically always during idle. how about retarded timing? if you fire to late, you wont burn all your fuel. not sure, but people say the main reason is the maf for these older nissans.

the ecu sets a target rpm for idle and tries just about anything to achieve that. the o2 sensor is not in play so it doesnt really have a way to know whether it is rich or lean. I dont think the ecu is measuring how much fuel is being sprayed from injectors and matching that to the volume of air as measured by maf.

[yukon]

A code 34 will make you run hella rich.

arent you supposed to check for a leaky injector?

The o2 is never ignored, ever. It may not directly control engine operation untill it recieves a signal from the CTS. Only thing that is controlled below a certain RPM is fuel cut, its directly in the FSM.

The primary o2 sensor doesnt register heat, its ussually 1 sheilded wire, thats triggered by the CTS. Yes it will go into closed loop operation within 1+ minutes depending on your cooling system. How do they not make sense durring idle? your using a pepboys o2 gauge huh. Ignore the o2 sensor, mine is probably bad from all the seafoam and marvel mystery oil ive used throughout my operations. The o2 has nothing to fucking do with your fuel system code.

directly from the fsm, the o2 sensor is ignored during idle. this might simply be because it never reaches a high enough temp to work. the o2 sensor readings are nonsense when the sensor is not hot enough and ecu knows enough to ignore the input. I dont think the cts has anything to do with the o2 sensor because my coolant temp is plenty hot during idle but O2 sensor is not hot enough to work right. sorry, but you are full of shit on a couple of your points.

[EDT007]

directly from the fsm, the o2 sensor is ignored during idle. this might simply be because it never reaches a high enough temp to work. the o2 sensor readings are nonsense when the sensor is not hot enough and ecu knows enough to ignore the input. I dont think the cts has anything to do with the o2 sensor because my coolant temp is plenty hot during idle but O2 sensor is not hot enough to work right. sorry, but you are full of shit on a couple of your points.

1) I know you've been here a whole month; :duh:; but telling people they know nothing on the subject or telling them are full of shit will get you nowhere fast!

2) As for your issue, you are correct. During the idle process the o2 sensor is put into "open loop" during idle. Although it falls under this condition and might not necessarily affect fuel trims doesn't mean that the ecu doesn't view it and check it against other values (TPS, timing map) to see that you are at idle and running rich therefore causing you to get the code. I'm not sure about this so you may want to check.

3) If you have access to the FSM then you saw this too:

http://i649.photobucket.com/albums/uu212/EDT007/idlespeedtest.jpg

[yukon]

good stuff.

[idlafie]

Since your car is 16 years old, when was the last time you checked your fuel pressure regulator?? If it is not functioning properly it could allow extra fuel thru the regulator and on to your injectors, causing you to "run rich" and kick a code.

This old Amorok list, (Amarok.Org (http://www.amarok.org/)), gives some good info...goes back to my days in my S14...now gone....

How a Fuel Pressure Regulator Works (http://www.240sx.org/faq/articles/fuel_pressure_regulator_wo.htm)

Smog tests are usually a good measure to let you know if your car is operating properly or not. I've seen a lot of my buddies S13's & S14's fail smog. Usually it's because of high Hydrocarbons, (HC) or Nitrogen (NO) readings. The cure is usually going back doing a tune up, (changing the distributor cap & rotor along with the spark plugs), checking the timing & idle & setting them to factory specs, (Use a FSM for this), along with checking the vacuum lines for leaks or tears and checking the secondary BPT & IAV valves & sensors, (the ones behind the engine block next to the firewall). A "running rich" situation usually ends up in crappy idle, poor fuel mileage, burnt out O2 sensors & a rotten egg smell from your catalytic converter and a Check Engine Light on your dash.....

Post your smog test readings so we can see what may be causing your "running rich" problem. I want to see what your NO readings are......Your engine uses your EGR system to help control NO & HC readings.

Hope this helps....

ID