Another_User

I have a strange problem that I can't quite figure out. My idle will dip to 400-500 rpms when coming to a stop after driving for awhile at highway speeds. The engine will also idle rough. I have a hotcam, shorties, lid, underdrive. Around town I don't get this dip, but the dip can cause me to stall out when I try to accelerate again. The only thing I can think of is that this is the only time my engine is badly heat-soaked. Because of my mods, can the PCM not compensate for some condition? Maybe a Volumetric Efficiency problem? I have HPTuners on the way for my 98 Z28, but I am not sure where to start. Is multiplying my VE table by 60-70% from 400-1200 rpms the place to start? Is it safer to calculate VE than to use that method? Is it safe to modify the VE table any higher than that, like to 1600 rpms? Thanks in advance for any info you guys give me!

SSean

Multiplying the VE table by 60% - 80% - 90% for 400 - 800 - 1200 rpm would be one place to start, dont go any higher than 1200. Sounds like you might also look into adjusting the idle air and IAC park positions tables. If you search, theres some pretty good info on idle tuning and hot-start issued

jimmyblue

iTrader: (11)

I would look first to raise the idle (like to 650),
and slow down the throttle follower decay rate.
Also get a good look at your ECT and whether
it is under control or swings way up once you
stop getting rolling airflow - fan settings maybe.
Hotcam is semi-notorious for idle issues and the
VE changes might help this out. I would say to
go by little bites there, just so you don't go past
the value that's really right, and right over the top
into crappy again.