Where's a good starting point for cold idle surging

[99LS1SS]

Here's my tune, config and a log from a few minutes ago.

The config is basically your config modified a little.

[99LS1SS]

It looks like all hell breaks loose right when startup airflow stops.

The STITs start pulling fuel immediately after the startup airflow stops. Could this mean that my VE or MAF are wrong at those ranges?

I am totally at a loss as to what is happening.

[99LS1SS]

After staring at the log for the last hour and a half, it looks like, either the Adaptive Idle Spark control or the Adaptive Idle Airflow (and maybe both of them) are being overly aggressive at correcting the idle. I'm leaning towards the Adaptive Idle Spark control since the STIT are staying sort of constant.

This is my best guess as to what is happening, and I wish I knew for sure. The commanded idle is 988 right before the hunting starts. The actual idle is around 1080 which is roughly 100 rpm off. The adaptive overspeed spark pulls -2.0 of timing and the idle drops. But, it drops too fast and it causes it to add 1.3 degrees of timing and it seems to seesaw back and forth from there. It keeps pulling timing out and then going too far and immediately adding roughly the same amount of timing back and it keeps over correcting itself until the engine heats up and the idle drops down to a more manageable level and the swings in timing get smaller until they fade away.

What I've done is taken the overspeed and underspeed timing and cut their values by roughly 60% under 150 rpm. I've also "smoothed" the Idle RPM step down so there aren't any large drops in the idle and it comes down at a smoother rate.

If none of this works, then I suppose I'll have a nervous breakdown and consider myself a crappy tuner.

What I've determined above all else is that, OCD is either a really bad thing or a really good thing if your a tuner. It just depends on whether you're good at tuning or not.

[edcmat-l1]

Post your latest tune an datalog. It's more beneficial to have aggressive idle spark control. It reacts much faster than the IAC can. Usually, if the base idle airflow is close, and the fueling is close, you won't have any surge. If there is, it has been my experience that it's caused more by an over active IAC than anything.

But, anyway, post up the tune and data log.

[Sam88gta1]

Here's my tune, config and a log from a few minutes ago.

The config is basically your config modified a little.

Here are what your OLFA table ,idle tables and Spark idle correction tables should look like.

[edcmat-l1]

Try this one out. Reset your fuel trims using the scanner controls. This one should cure it for you.


Attachment 32692

[99LS1SS]

Here's this morning's log and tune. I took your advice and moved the under/overspeed back to where they were. It still hunted for idle though. I feel like there is something obvious missing. Does my VE look jacked up? I tuned it multiple times to get it close.

[edcmat-l1]

Did you try the tune I posted?

[edcmat-l1]

You need to include MAF Hz in your PIDs and then setup your MAF STFT histogram, and dial in the MAF. Your fuel trims are -20% as soon as the go active. Get those dialed in first. It's still an isue of too much fuel.

Did you reset your fuel trims using the scanner controls?

[edcmat-l1]

Try this one. MAKE SURE YOU RESET YOUR FUEL TRIMS!!

Attachment 32698

[99LS1SS]

Yes. That is it with the exception of a slight MAF change at idle. I saw the fuel trims and dropped my MAF settings back down. I'll log another idle at lunch and post it up.

[99LS1SS]

Try this one. MAKE SURE YOU RESET YOUR FUEL TRIMS!!

Attachment 32698

Lol. I reset my trims before every idle log.

[99LS1SS]

Out of curiosity and for my knowledge, edcmat-|1, what is the reasoning disabling the LTFT?

I've made the most recent changes. Unfortunately, I didn't have my computer when I had to start the car last time so it will be a little while before it cools off. I'll post up though.

Thank you for the help so far!

[99LS1SS]

Guys, since no suggestions have worked completely, I'm going to start back with the basics and make sure my VE and MAF are dialed in again. I have a feeling one or both of those are haunting me. I "thought" I had dialed them in correctly but, the longer this goes on the less I'm sure of that. I'll log my VE Error tomorrow morning and see if I can see anything obvious.

[99LS1SS]

What I've done that seemed to help as much as anything is to drop my Open Loop EQ table to all 1's down to 30 degrees.

[Ben Charles]

What I've done that seemed to help as much as anything is to drop my Open Loop EQ table to all 1's down to 30 degrees.

Cant really go Stoich at cold ECT's the engine needs fuel. If it runs well at 1, then your Ve/MAF tables are incorrect

[99LS1SS]

I would bet my VE is off if that is in fact the case.

Can you give me a good VE config to start tuning my VE?

[99LS1SS]

Here's a log from this morning's cold start. It stumbles at startup but it doesn't have the hunting throughout the temp range like it did.

[Ben Charles]

You need more startup airflow at the 30-48 ECT, notice how you max out idle desired at 40g\sec and STIT's are almost maxed out, I would crack open that TB some or port of that IAC in that 90mm TB. Your IAC at hot idle is 100, so yea crack open that TB, may have to do a small drill mod. I PROMISE you get more air at startup it will run better.

[99LS1SS]

Just so I am not adjusting the wrong tables. Are you referring to the Startup Airflow Initial table or the Base Running Airflow Idle Airflow table?
I will crack the TB some too. There's already a hole in the TB blade.