Greetings!

I have a TPI 5.7 sitting in front of a 5 speed. I'm running a 730 w/8D using S_AUJP_V3. I copied all the manual trans throttle follower stuff from an 8D manual trans prom into the SAUJP and everything seems to work pretty well.

I idle however need some work. Warm idle hunts up and down by about 100-150 RPM. I set my target idle to 625 RPM. I've sent my minumum air to about 625 RPM in neutral and adjusted the TPS to .54v.

Watching my TTS data, I see the IAC counts hang around 13-15 as the idle hunts, but I see the timing jump from 29 to 19. Even with the IAC disconnected, the idle will still hunt, so I think my problem is caused by the timing changing so much. In my main spark table, my neutral idle timing is set to 20 deg advance.

I do not have any vacuum leaks that I know of, and my idle was pretty good when I was running a 165/MAF setup before.

Any ideas what would make my timing jump up and down creating a hunt like this?

I can email a TTS log of my idle hunting if anyone wants to see it.

Thanks!
Dieter Kedrowitsch

 

8D has an Idle SA table.
It has a TPS qual and I think a MPH qual.
There are also Spark adv/ret constants based on error.
Make sure your VE is smooth in the idle are too.

Did you copy all the IAC settings? Not just the TF settings.
Not all of them are listed in the available xdf's.
IDK if TC has all of them.
But the MT stuff is tuned a bit faster IIRC.

 

Try setting the SA at 600-800rpm to be 19°, through all loads you experience at idle (like maybe 25kpa to 50kpa, depending on the cam).

 

I might try using the AXXD 305 M/T bin, with my VE tables copied over as well as some other doo-dads I like from SAUJP. I really _hate_ the fast M/T idle, and I have it working very nicely with SAUJP where the throttle follower between gears is there, but when I come to a stop the motor idles right down to 625 like a nice smooth automatic.

I like the idea of bringing the timing down to 19deg at idle, since at 625RPM, I'd expect the 24-28deg advance the M/T bin has might cause some "caughing".

The vehicle is a 92 Chevy 4x4. I'm swapping an automatic drivetrain into it very soon, so most of this won't matter...but I drive it as an every-day driver so the hunting idle is really annoying.

By the way, it's a 100% stock L98 with the stock roller cam from an 87 GTA. The motor only had 62K miles on it so all I did was put a fresh set of bearings, seals, gaskets, fresh paint, and bead blast the intake, runners, and plenum before sticking it in the truck.

 

Well the AXXD helped the hunting, it's pretty much gone. It keeps the timing to about 22deg at idle, but I notice it must be hitting the idle RPM correction timing thing, where it adds about 5deg because the idle constantly jumps between 22-27deg. Normal? Oh and my shift light works again.

My idle according to DataMaster:

RPM: 650
MAP KPa: 39
LT BLM: 125
Fuel Trim Cell: 4
TPS: 0.57v
IAC POS: 13
Spk Adv: 22.1
CTS: 201 F

Throttle plates adjusted for 600 RPM warm idle in neutral with IAC fully closed.

But my idle still isn't so hot, and I had that problem when I was running MAF too. The idle has a 'stumble' to it. I'll post a new topic for this problem.