Unstable Idle Lambda ( AFR )

[510fever]

I noticed recently on my wideband that the idle lambda is very unstable using my Apexi PFC. I dont use closed loop control and still find that my AFRs cycle +/- 0.7 ie if I tune the idle to 14.7 it will vary between 14. to 15.4 with a frequency of about 0.5 hz. THe car has a lumpy idle even at 1000 rpm, so I am pretty sure it has some aggressive cams in it. Would that cause these symptoms?

On another note I have to complain about the PFC intake air temp correction. I find day to day idle AFR differences of +/- 2! some days I idle at 13:1, other days it may be 16.5:1. Is this normal or might I have a serious problem?

[LeKing]

I noticed recently on my wideband that the idle lambda is very unstable using my Apexi PFC. I dont use closed loop control and still find that my AFRs cycle +/- 0.7 ie if I tune the idle to 14.7 it will vary between 14. to 15.4 with a frequency of about 0.5 hz. ?

ok this might help it depend on your feedback if its ON or OFF. O2 feedback..
i got my car tuned & my tuner said to me keep your feedback OFF cause i tuned your car without your o2 sensor. left the shop car was leaning out so turn it ON again well big mistake had to restart the power fc all over again.

It started to do it again so he told me to unplug both o2 sensor all OK now this was my problem...hope this help:-)

[510fever]

I have disabled 02 feedback. This symptom is still present unfortunately.
Anyone else have ideas? would a vacuum leak cause a fluctuating AFR or would it just cause a leaner than usual afr and steady but higher than usual intake manifold pressure?

[Dragon Humper]

Could be a few missfires at idle mixed in with your cam lumpiness messing with your readings. Do you have the L-jetro? I have a D-jetro and NO o2's are even hooked up. Looked for half an hour trying to find the o2's to change them out only to find none are present.

I have a few misses at idle too and my Lambda is all over the place when that happens.


Jon.

[kelaog]

I'm beginning to think the PFC is a pile of **** for idling. I couldn't get my GTR to idle properly with the PFC either. It would hunt and then find a spot then hunt =/ It's annoying. Eventually I just either leaned it out or richened up the idle and it would be stable but messed up AFRS.