Isolated idle surge to certain ECTs in gear

[BADFNZ]

So I've been on a very long journey to fix my idle surge. A lot of suggestions from my previous thread have helped immensely. Now I only have surge from certain ECTs while in gear.

I'm attaching 2 logs. The first shows the surge between 73-100* ECT and the second shows the surge between 88-115*. I'll also attach my latest tune. STITs are solid throughout, but the surge throws the numbers off. It seems when the surge starts, STITs are about -2 g/sec. I also notice the ETCs in question are right at the transition between the 68* and 104* cells in the histogram. Any input is highly appreciated.

Also, on an unrelated note, does anyone know why only the first 2 histograms work and the rest say they're not supported?

[gn2beatu]

Your timing is quite high for idle timing, especialy the in gear timing (24 degrees). Set your idle RPM ranges to 14 degrees and see if that helps. Thats where most of the cars I have seen like the timing to start with. (remember you can always add some back)

If that fixes it great, if not, it should at least help a bunch. After you lower that, the rest should be easy to dial in. I had a similar issue recently where a tune was set at 18 degrees in P/N and the computer ended up with bad surging, set it at 14 and was almost rock solid. Just needed a minor tweek to the Base RAF. G/L

[BADFNZ]

Thanks for the response.

The timing data is from a tune Russ K posted for me. The P/N timing he posted was around 14*, but when I upped it to 18* using the Spark Idle command, the idle seemed to get slightly better. When in gear, the Spark Idle command doesn't work because the idle automatically starts surging. This obviously tells me the idle in gear relies on changing spark values and won't hold with a steady value.

[gn2beatu]

You are correct, it changes the timing to control the idle. Also changes the B.R.A.F.

Go back to 14* and play with your B.R.A.F. Look at the scanner and see what value its commanding at idle. EX: .800 Then either raise or lower the table 10% depending if you need to increase or decrease the airflow. If your not sure, pick one, it will get worse or better. You will get it after a few tries. G/L

[BADFNZ]

Well my P/N idle is fine, it's the in gear that's having issues.

The reason I don't think it's timing is because it only happens during a certain ECT. If it was timing, wouldn't it be the same throughout? I'm still new so please tell me if I'm wrong here.

[gn2beatu]

Did you drop the timing in the in gear like I suggested. Cause thats where your running 24 degrees. Notice the P/N timing is lower, and it DOESNT do that, thats why I say drop the timing. All then new stuff has low timing at idle. Keep in mind the computer can add or take away timing to increase and decrease the idle if needed. You just need a good base.