Occasional high idle and no closed loop

[MysticBowtie]

MS3 Pro
Engine - Supercharged GM V8 LT1 (1997)
Ignition - GM LS1 ignition system
DATA LOG IS 4MB (too large) I can email it if you're willing to look at it.

(EDIT - the datalog is too big to upload 4MB, I'd be very happy to email it)

I've been trying to dial in the car while driving, and occasionally have a problem with the car idling up from the normal 850ish to 1500-1900 RPM. When this happens, it is sudden and can happen after simply accelerating, or turning the car off when at normal operating temp and turning it right back on. Today I caught it all on a data log while idling in the garage.

I was trying to get the idle better, and get the car to go into closed loop. I didn't gas the throttle, but just wanted the MS3 to do it's thing and adjust the idle for my pre-set values. It didn't ever get to closed loop, nor did it try to adjust to meet my AFR target of 14.7. I gave it under 10% throttle, and after that, the idle wouldn't go back down. I did notice that the TPS never went back to 0, but instead seemed to be happy at .3%. I have tightened the throttle body spring and solved that problem, but it's too late to start the car and re-log (infant next door). It doesn't idle up until 23,277.238 seconds into the log after I goosed the throttle 10%.

The weird part - I found that if I give it 3% throttle, the IAC will close, and the car will actually drop RPM until I release the throttle and it re-opens the IAC and idles back up. This can be seen at 23,494.963 and forward in the datalog.

I noticed that the I/O Pins list shows that I have an IAC1 and IAC2. My car only has a single IAC. Is this perhaps my problem? I can't find where I can turn off IAC2.

So, #1 - why won't my car go into closed loop
#2 - why does it idle well, then occasionally jump up the RPM by opening the IAC
#3 - The car will start with little to no gas on the second turn of the key, never the first - any suggestions to fix that would be an added bonus!

I really appreciate any help, I've been trying to figure this out for 2 days. Thanks for any help guys!!

Ben

[turbo conversion]

Are you using the stock GM IACV?

David

[billr]

Increase the homing steps, make sure it is going full closed and stalling there to find "home". Maybe turn off "closed loop" and get things stable with "open loop" first?

Edit: Just take a short log to post here... so easy to do!

[MysticBowtie]

Are you using the stock GM IACV?

David

Yes sir.

[MysticBowtie]

Increase the homing steps, make sure it is going full closed and stalling there to find "home". Maybe turn off "closed loop" and get things stable with "open loop" first?

Edit: Just take a short log to post here... so easy to do!

In open loop, it idles well. I'll take a short log of it. And post it a bit later today. Thanks for the interest!

Ben

[turbo conversion]

Are you using the stock GM IACV?

David

Yes sir.

On a stock GM IACV all four wires (IAC1A-IAC1B-IAC2A-IAC2B) will need to be wired correctly for it to function
or did I miss understand your first post?


David

edit: wording

[MysticBowtie]

The first file, "Rough Low Idle," shows the IAC being fully open causing high RPM until I give it a minimum of 2% throttle, which then lets the IAC valve close and try to act what I would call normal, trying to correct for a good idle.

EDIT BELOW
Hard to start - Takes two turns of the ignition, but no added throttle (It never starts on the first try): The data log named, "Hot Start - Rough Low Idle Drop," shows the car at operating temp at startup. It starts on the second try with zero throttle input as per usual. Then the idle drops low and when the IAC valve opens to full, there is no recovery. My thought is that the idle screw on the throttle body needs to be opened a bit more.

Thank you!

Ben

[muythaibxr]

Not necessarily related, but I would set PID ramp to target to something other than 0.

The real cause of the problem is the Max Decel Load.

It has to be above the value you set (25) for PID delay seconds before PID will activate. Load is dipping below your setting (25) several times in the log you posted. Closed loop never actually engaged in your log. Not even once.

Ken

[MysticBowtie]

Ken,

Thank you so much, that got it into CL!!

As far as the idle goes, it is still hunting for the 850 RPM that I have it set for, generally going low (around 550-600). The AFR seems to read pretty good, but the motor is on the verge of dying the whole time. I adjust the the idle screw and reset the TPS calibration, and that doesn't seem to be helping. It will eventually hit a point that the RPM just jumps up to 1500, then I back the screw out, and it goes low. I'm thinking the plugs might be fouled at this point, do you see anything else on this recent log that would lead you to believe I have something in the tune jacked up?

Off topic, I noticed your username. I used to train under Saekson Janjira here in Plano. Do you still fight/train?

[turbo conversion]

You may want to also try setting the algorithm under idle control to IAC Closed-loop always-on instead of IAC Closed-loop moving only.

David

[MysticBowtie]

You may want to also try setting the algorithm under idle control to IAC Closed-loop always-on instead of IAC Closed-loop moving only.

David

Thanks David. I'll do that.

Ben