rel3rd

iTrader: (43)

I rarely even drive my car, but cannot seem to shake this surge and intermittent sticky/hanging idle. I'm wondering if maybe my throttle blade screw could have backed off slightly or something, since it seems to be fine for a few drives after making a tune change, then it's back to acting up again.

The car runs great at highway cruise, and at WOT, but also has started bucking at low rpm's recently. This was never an issue in the past.

Cam is what most call a "baby" cam, 226/226 duration @.050" and on a 112lsa.
Throttle blade was drilled a year ago...long before any idle issues.
MAF meter was de-screened, also over a year ago.
Car is an A4 with 3600 stall lockup converter.

I attached my current tune and cold start scan, and I hope that the config was RussK's, since that was what I thought I used.

Any ideas/advice/suggestions welcomed and appreciated...

It's almost like all the time spent trying to get idle squared away has been wasted because right now it idles like I just did the cam swap yesterday. It actually stalled this evening while warming up, coasting through my neighborhood. I have tried several different idle tunes, and even used alot of the idle suggestions in the stickies, and nothing has seemed to work for more than a few drives.

RedHardSupra

iTrader: (1)

surging is overfueling, hanging idle is RAF. both topics have been beaten to death and then some on all the forums. may the search button be with you

SSpdDmon

iTrader: (10)

surging can be too much timing too.

jimmyblue

iTrader: (11)

One thing I have never seen discussed, is how to
change the PID filter constants on the idle RPM
loop to get better stability. The fueling and spark
mentioned, are really changing the fundamental
dynamic response of the engine to incremental air.
When you're pig rich a little more air is "so what?",
the motor is slow to ramp and the idle RPM loop
overtravels before it gets what it wanted.

If you lock the IAC with bidirectional controls
and the surging ceases then you've got an idle
RPM loop problem of this sort.

However, there is also a fuel "loop" that I have
had problems with, which I think is the inaccuracy
of the MAP-axis slope of the VE table. Some get
improvement from messing with the filtering on
this (the filter for cell-cell transitions) but if you
are seeing injector pulse width swinging a lot more
than (MAP*RPM) ought to dictate, maybe the VE
table's slope in the MAP dimension wants some
correction. My gut says the mechanism is MAP
based fuel overshoot / undershoot that keeps
on kicking the mixture, which MAP then follows
and chases its tail. Again you can experiment
with the bidirectional controls, lock AFR and see
if leaner or richer helps you out.

Remember that with any high overlap cam, 14.7
by the narrowbands or wideband O2 sensor is
not 14.7 in-taken; there is a lean error from air
in the exhaust especially at lower RPM and a
true-stoich mixture is going to be indicating a
15.x:1 AFR probably.

To this end, you might tamp down the O2
switchpoints in the idle-range airflow mode cells
until you see WB readings in the 15:1 range
when NBO2s are switching densely enough for
proper CL operation. That may do more for your
idle mixture, than VE tweaking (if CL is defeating
/ undoing your changes by mis-trimming).

rel3rd

iTrader: (43)

If I had found any DEFINITIVE answers while searching, I would not have made a thread containing a cold start scan and a copy of my tune.

Thanks for the replies so far guys.

jimmyblue, I will try to use the vcm controls to isolate problems and see what it (hopefully) tells me.

FWIW, I re-flashed a tune from about 7 months ago, today. This was a tune that was fine for 5 months, then suddenly started with the sticky idle when coasting. It was modified by russk, who helped me out on the HPTuners forum, as well as Frost, an LS1tech sponsor. Ironically, all of the idle/fuel and timing parameters are the ones before anyone made any changes, which really has me baffled...So far today, it's been great...

chevyls10

iTrader: (2)

Your low octane timing table has more timing in the idle areas than the high octance table. Match the two in those areas and maybe increase another degree and see what happens

rel3rd

iTrader: (43)

Don't know what happened there...

Anyway, here is present tune...pretty much back to square one and trouble free so far...

RedHardSupra

iTrader: (1)

all wrong timing does it allow not enough/too much time for the mixture to burn, effectively just altering the mixture...so we're back to fueling, not just commanded, but effective.