Rich/lean idle condition

[91GSXeclipse]

When at idle (usually at warm up and during turbo time) the car will go back and forth rich and then lean usually 11 afr to 16 arf. The car is tuned perfectly and will sit at stoich most of the time but every once in a while it will go rich and then lean. The car idles normally with no error codes and no obvious changes on the logger? I have been told that a leaky TB can cause weird conditions like this. I havent completed a boost leak test since I installed injectors, im not sure if a vacuum leak would cause this condtion though.

[viprez586]

vac/boost leak test it.
Idle AFR should be 14.7-15.0

[GST racer]

depending on what the outside temp is, its alright if it goes lean. mine is tuned perfectly.. but at idle it'll cycle between 13.0 to 17.5 or so.

the car isnt gonna predetonate or burn up cylinders at idle. just make sure the afr cycles, and doesnt stay lean or rich.

[steve]

You may be describing closed loop operation. The ECU raises and lowers the AFR to try and average 14.7:1 during idle and cruising, this causes the front O2 sensor to switch between lean and rich. If you sensors is getting old it can take a while for it to register the change and cause a wider swing in AFR.

[91GSXeclipse]

Originally Posted by steve

You may be describing closed loop operation. The ECU raises and lowers the AFR to try and average 14.7:1 during idle and cruising, this causes the front O2 sensor to switch between lean and rich. If you sensors is getting old it can take a while for it to register the change and cause a wider swing in AFR.

Possible but my front O2 is only about 6 months old. The part that really confused me is that the car has never searched that hard before. That is why it is leading me to believe that there is some other hidden problem.

note. the only time the idle will change at all is when it gets super rich other than that it doesnt surge at all.

I plan on doing a boost leak test just to make sure. I also ordered a EGR block off plate so I can get rid of all the uneeded vacuum lines

[steve]

Originally Posted by 91GSXeclipse

Possible but my front O2 is only about 6 months old. The part that really confused me is that the car has never searched that hard before. That is why it is leading me to believe that there is some other hidden problem.

note. the only time the idle will change at all is when it gets super rich other than that it

Your original post doesn't talk about surging or any other idle issues, just the AFR changing.
It says:

Originally Posted by 91GSXeclipse

When at idle (usually at warm up and during turbo time) the car will go back and forth rich and then lean usually 11 afr to 16 arf. The car is tuned perfectly and will sit at stoich most of the time but every once in a while it will go rich and then lean. The car idles normally with no error codes and no obvious changes on the logger?

Perhaps if you clarify your question.

[GST racer]

i think he means the car will sit at stoich, but then go lean or rich, and without words basically said the rpms rise or fall as the a/f ratio changes.

[91GSXeclipse]

Originally Posted by GST racer

i think he means the car will sit at stoich, but then go lean or rich, and without words basically said the rpms rise or fall as the a/f ratio changes.

Your right.... Sorry I didnt clarify that much better I was kinda in a hurry when I last posted.

I just recieved a used TB that I will install soon as well as the EGR block off plate. Its supposed to be a little warmer here on tuesday so I will change it all out then and perform the much needed boost leak test.

I should have added that when the AFR symptoms started the car also started to get a slow battery drain. I have since swapped the ecu back to my old non-eprom ecu which has appeared to have stopped the battery drain but the AFR symptoms remain.

The eprom ecu was rebuilt and socketed but the symptoms that the car was giving me lead me to believe that the ecu was to blame....... guess not

[91GSXeclipse]

well after a little more trouble shooting.... found that after watching the logger VERY CLOSE that the air flow rating was dropping off to 0 for a split second which was making the car default to rich, then the ISC was stepping to lean it out. this is why the car was going from rich to lean..... replaced the MAF and presto!!! problem fixed.

As for the battery drain, I have a backup batter for my viper alarm system.... needless to say the battery for that is 4 years old and decided to die on me which was draining my red top.

Also, I installed the EGR block off and eliminated a bunch of vacuum lines.... what a difference

[spyderturbo007]

Glad you got everything figured out and thanks for posting your results. That will help people in the future.

You might want to mark this thread "Resolved".