Warm Idle Surge

[WS6FirebirdTA00]

I am having an odd issue on some warm starts.

If I start up after a few hour cool down I get some surging (log attached).

The only idle parameters changed in the factory tune was to bump up the hot idle area 100 RPM (tired of giving it too much throttle to get moving) and blended that back to the stock value at 32C/90F.

I don't have idle control issues at any other time and after about 10 seconds of this it stabilizes.

I notice during this time the spark, throttle position and intake valve temperatures are all fluctuating.

This issue only happens when it has the higher startup airflow. If it starts without the adders (which I can't find in the log or tune) it does fine. In the tune the factory adaptive idle integral min is set to 0, but the other cells are -50. I see several other stock files like this. I was curious if that would have any impact, but I would expect issues elsewhere.

[Camaro6]

Post the tune since a few items can do this. Stock and modified tune preferred.

[WS6FirebirdTA00]

Here you go. Stock tune/reverted back to stock with just the idle speed changes. Same issues. I was trying to see if this was an issue even factory.

It does not do it hot, it does not do it cold. It seems to only do it in the 50C-65C ECT/oil temp range.

From what I see in the log, the spark and throttle position are constant and the RPM starts to creep up over the 1200 RPM command. Then the throttle tries to close and the spark starts to go up (less TM spark). It flares up and then seems to over correct. It goes through a few cycles and then the commanded drops from 1200. I assume this is when the startup decay expires. Then it gets into what I then assume to be adaptive idle and fixes itself as the RPM continues to lower to commanded.

The only table I see that would impact this would be the idle external load, but I am not sure if that is active if startup hasn't fully decayed. There are some odd jumps between 1000 and 1300 RPM and also around 50C oil temperature. I tried a lower 1300 RPM value, just not a lower 1000 RPM value yet. That was going to be my next guess.

I am not seeing any obvious tables for startup airflow, startup decay, idle spark/correction, etc. Truck is stock except for Airaid intake tube and GM Borla catback.

[WS6FirebirdTA00]

I also noted in some 2017 files the cat warmup max ECT is 43C vs 66C in mine.

I wonder if that could be part of this issue and also my hesitation I feel on warm restarts? It may be pushing the limits to improve emissions but hurting dravability.

[Camaro6]

I also noted in some 2017 files the cat warmup max ECT is 43C vs 66C in mine.

I wonder if that could be part of this issue and also my hesitation I feel on warm restarts? It may be pushing the limits to improve emissions but hurting dravability.

Check that your MAF is installed correctly and your CAI for any leaks (unmetered air) since it's lean when doing it and more at a higher rpm. Do you have a driving log since no MAF was changed or VE table. You should be able to keep the stock idle rpm no problem on this setup.

You mean the car not wanting to drive on a warm restart? You have to push the pedal more to get the truck to move? It's commanding too much timing and tq mgt is engaging heavily. That's what I noticed originally when I watched the log. Try zeroing out the "Cold Launch Spark" table and see if that fixes it. Or log cold spark launch advance & time since start and see if it happens when this is engaged and alter it accordingly. It does correct at the 20sec mark, so I'm leaning towards this but make sure MAF and CAI is correct. After 158eng temp CLS doesn't effect anything.

[Camaro6]

Also, when I went to E85 I had a bit to much air flow on cold starts and had to change the idle external load otherwise tq mgt kicked in and bounced the idle a little. On 93 with 50rpm higher it didn't do it though.

[Camaro6]

That is how much I increased the table from stock, but I have flex fuel sensor and was due to E85. Hope all that info helps.

IEL Chg.JPG

[WS6FirebirdTA00]

Thanks for the replies.

The MAF has been tuned, I just went back to stock to see if anything I changed in the timing tables or somewhere else may have affected it. Honestly, the only table I saw that would have any potential impact was the high octane, if that is even used around idle. I know the old calibrations did not.

The intake tube is on good. It has the factory filter housing, so I never touched the MAF. Cold start, hot start, driving, no issues until the ECT drops back into the 50C-60C range.

I did notice the older cals had cat warmup end at 43C ECT. Mine factory was 66C. I lowered it back down to 43C, so when the ECT is in the problem area it no longer calls for a higher idle for cat warmup.

For the warm restart, the truck would go but it was acting like it was misfiring. The torque management timing was pulling so much (because of cat warmup) I think that was causing the feeling at very light throttle (2-4%). I also looked at the cold launch spark and was getting 0 deg the entire time.

I was planning to make more changes to the external load table. I had some high values at 1300 RPM and this was happening at 1200 RPM. I lowered those and saw no improvement. My next shot was to attack it more and also lower the 1000 RPM area. The fact that everything was idling find outside of cat warmup in those areas, I decided to lower that as my next step. I really don't want it to idle at 1200 RPM for a minute when everything is still pretty hot.

Do you have your stock external load table you can post or comparison?