Oscillating Idle when cold from 93 to 140 deg ECT

[Ls1c5vette]

2000 Corvette with LS3 swap (Still using LS1 sensors). Starts and idles fine till about 93 ECT, then RPMs start to go up and down, it does this till about 140 ECT then smooths out and idles great. I dont think its fuel as its a dead set 14.6 at hot idle open loop, could it be proportional or integral idle?. Scanner and tune posted below.

[edcmat-l1]

Don't touch the idle adaptives.

First thing is, double check your injector data.

Second, apply the 1 bar COS to get off the secondary VE table.

But the root cause is WAY TOO MUCH idle timing, and not aggressive enough over/under shoot.

[Alvin]

I agree too much timing at idle.

Shoot to center the idle around 18 degrees. You want to be able to go up in timing to save an idle dip and lower to pull an idle down. This is sitting in the high 20's at idle which leaves no room to go but down.

The VE doesn't look proper for this cam/setup.

Put the IAC setups vs effective area back to stock. There are no IAC steps on this setup but I'm fairly sure it still references that table for the ETC scalar.

[Ls1c5vette]

Appreciate the info guys, that fixed the issue. Went to 1 bar SD as well. She does dip about 100 RPM below set point when coming off the throttle from higher rpm but it recovers quickly.

[Alvin]

Appreciate the info guys, that fixed the issue. Went to 1 bar SD as well. She does dip about 100 RPM below set point when coming off the throttle from higher rpm but it recovers quickly.

The whole tune is going to have to come together. There won't be one little fix here or there.

[SiriusC1024]

He's not too far off. Better VE, a little touch on throttle cracker and follower...

[Ls1c5vette]

Any idea what I could adjust to get rid of small bucking under light load from 1400-1600rpm? Fueling is spot on and I?ve tried different timing points in the vcm scanner (20, 25 and 28 degrees) but it still does it. I?ve also tried to zero out the TC table and it still does it.

[edcmat-l1]

Put a stock camshaft in it. You didn't mention cam specs but I'd bet it's a GMPP LS3 crate motor with a lumpy cam. If you want stock driveability put a stock cam in it.

[Ls1c5vette]

It has a small texas speed stage 1 cam in it. They claim it drives like stock and I have to agree it does, minus the stupid bucking 1400-1600

[SiriusC1024]

Disable spark smoothing.

[Alvin]

It has a small texas speed stage 1 cam in it. They claim it drives like stock and I have to agree it does, minus the stupid bucking 1400-1600

what are the actual specs and I'll tell you if it's normal or not.

A lot of issues like this will resolve themselves after the tune comes into shape. So if the fueling/ve or timing is wonky you'll get bucking. It can also be 02 sensor delay/integral induced.

Disable spark smoothing.

[edcmat-l1]

Disable spark smoothing.

Agreed that is typically the fix if it's still enabled.

[Ls1c5vette]

what are the actual specs and I'll tell you if it's normal or not.

A lot of issues like this will resolve themselves after the tune comes into shape. So if the fueling/ve or timing is wonky you'll get bucking. It can also be 02 sensor delay/integral induced.

Disable spark smoothing.

225/236 .629"/615" 114 LSA, 109 ICL. Ill try to disable spark smoothing

[bk2life]

It has a small cam in it.

225/236 .629"/615" .

"small cam"

[SiriusC1024]

I re-read your original problem statement. OLSD tuned. It's still in CL STFT. Look at what the fuel trims are doing. 10% rich. Tune VE with the narrowbands up to 85kPa. The O2's are switching great in the log. No need for OL, which is an assumption people make. Tune VE. It's very much a rough draft.

With that large cam I'd recommend EOIT adjustment.

BRAF need adjusted, as STIT+LTIT is showing a lot of air being added.

Lower idle spark.

Then there's the other things mentioned previously that'll help. Really, there's a lot more to be done.

[Alvin]

225/236 .629"/615" 114 LSA, 109 ICL. Ill try to disable spark smoothing

That should be easy to tune all the buck out except light/ zero pedal situations in like parking lots, low speed.

[Ls1c5vette]

I re-read your original problem statement. OLSD tuned. It's still in CL STFT. Look at what the fuel trims are doing. 10% rich. Tune VE with the narrowbands up to 85kPa. The O2's are switching great in the log. No need for OL, which is an assumption people make. Tune VE. It's very much a rough draft.

With that large cam I'd recommend EOIT adjustment.

BRAF need adjusted, as STIT+LTIT is showing a lot of air being added.

Lower idle spark.

Then there's the other things mentioned previously that'll help. Really, there's a lot more to be done.

Thats a old log file, BRAF is inline now (+/- .75) and VE is spot on as well (fuel trims 2%), idle spark is now at 20. I played with the excel sheets found online and got a true normal EIOT of 6.2 so for now I split the difference from the 5.55 and made it 5.80 to see how it goes. If I should just run the 6.2 as its calls for in the sheet then please let me know. Appreciate all the help thus far.

[Ls1c5vette]

Ok, I went with 6.10 on the EOIT, massive difference, lots more low end torque starting out from a stop and the smell of raw fuel is gone. Wish I would have tuned this table to begin with. Bucking at 1400-1600 is 85% gone.